pkg/analyzer/lib/src/dart/analysis/driver.dart

// Copyright (c) 2016, the Dart project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

import 'dart:async';
import 'dart:typed_data';

import 'package:_fe_analyzer_shared/src/macros/executor/multi_executor.dart'
    as macro;
import 'package:analyzer/dart/analysis/declared_variables.dart';
import 'package:analyzer/dart/analysis/results.dart';
import 'package:analyzer/dart/ast/ast.dart';
import 'package:analyzer/error/error.dart';
import 'package:analyzer/error/listener.dart';
import 'package:analyzer/exception/exception.dart';
import 'package:analyzer/file_system/file_system.dart';
import 'package:analyzer/src/context/packages.dart';
import 'package:analyzer/src/dart/analysis/byte_store.dart';
import 'package:analyzer/src/dart/analysis/driver_based_analysis_context.dart';
import 'package:analyzer/src/dart/analysis/feature_set_provider.dart';
import 'package:analyzer/src/dart/analysis/file_content_cache.dart';
import 'package:analyzer/src/dart/analysis/file_state.dart';
import 'package:analyzer/src/dart/analysis/file_tracker.dart';
import 'package:analyzer/src/dart/analysis/index.dart';
import 'package:analyzer/src/dart/analysis/info_declaration_store.dart';
import 'package:analyzer/src/dart/analysis/library_analyzer.dart';
import 'package:analyzer/src/dart/analysis/library_context.dart';
import 'package:analyzer/src/dart/analysis/performance_logger.dart';
import 'package:analyzer/src/dart/analysis/results.dart';
import 'package:analyzer/src/dart/analysis/search.dart';
import 'package:analyzer/src/dart/analysis/session.dart';
import 'package:analyzer/src/dart/analysis/status.dart';
import 'package:analyzer/src/dart/analysis/testing_data.dart';
import 'package:analyzer/src/dart/analysis/unlinked_unit_store.dart';
import 'package:analyzer/src/dart/element/element.dart';
import 'package:analyzer/src/diagnostic/diagnostic.dart';
import 'package:analyzer/src/error/codes.dart';
import 'package:analyzer/src/exception/exception.dart';
import 'package:analyzer/src/generated/engine.dart'
    show AnalysisContext, AnalysisEngine, AnalysisOptions, AnalysisOptionsImpl;
import 'package:analyzer/src/generated/source.dart';
import 'package:analyzer/src/lint/registry.dart' as linter;
import 'package:analyzer/src/summary/api_signature.dart';
import 'package:analyzer/src/summary/format.dart';
import 'package:analyzer/src/summary/idl.dart';
import 'package:analyzer/src/summary/package_bundle_reader.dart';
import 'package:analyzer/src/summary2/ast_binary_flags.dart';
import 'package:analyzer/src/summary2/bundle_writer.dart';
import 'package:analyzer/src/summary2/macro.dart';
import 'package:analyzer/src/summary2/package_bundle_format.dart';
import 'package:analyzer/src/util/file_paths.dart' as file_paths;
import 'package:analyzer/src/util/performance/operation_performance.dart';
import 'package:analyzer/src/utilities/uri_cache.dart';

/// This class computes [AnalysisResult]s for Dart files.
///
/// Let the set of "explicitly analyzed files" denote the set of paths that have
/// been passed to [addFile] but not subsequently passed to [removeFile]. Let
/// the "current analysis results" denote the map from the set of explicitly
/// analyzed files to the most recent [AnalysisResult] delivered to [results]
/// for each file. Let the "current file state" represent a map from file path
/// to the file contents most recently read from that file, or fetched from the
/// content cache (considering all possible file paths, regardless of
/// whether they're in the set of explicitly analyzed files). Let the
/// "analysis state" be either "analyzing" or "idle".
///
/// (These are theoretical constructs; they may not necessarily reflect data
/// structures maintained explicitly by the driver).
///
/// Then we make the following guarantees:
///
///    - Whenever the analysis state is idle, the current analysis results are
///      consistent with the current file state.
///
///    - A call to [addFile] or [changeFile] causes the analysis state to
///      transition to "analyzing", and schedules the contents of the given
///      files to be read into the current file state prior to the next time
///      the analysis state transitions back to "idle".
///
///    - If at any time the client stops making calls to [addFile], [changeFile],
///      and [removeFile], the analysis state will eventually transition back to
///      "idle" after a finite amount of processing.
///
/// As a result of these guarantees, a client may ensure that the analysis
/// results are "eventually consistent" with the file system by simply calling
/// [changeFile] any time the contents of a file on the file system have changed.
///
/// TODO(scheglov) Clean up the list of implicitly analyzed files.
class AnalysisDriver implements AnalysisDriverGeneric {
  /// The version of data format, should be incremented on every format change.
  static const int DATA_VERSION = 311;

  /// The number of exception contexts allowed to write. Once this field is
  /// zero, we stop writing any new exception contexts in this process.
  static int allowedNumberOfContextsToWrite = 10;

  /// The scheduler that schedules analysis work in this, and possibly other
  /// analysis drivers.
  final AnalysisDriverScheduler _scheduler;

  /// The logger to write performed operations and performance to.
  final PerformanceLog _logger;

  /// The resource provider for working with files.
  final ResourceProvider _resourceProvider;

  /// The byte storage to get and put serialized data.
  ///
  /// It can be shared with other [AnalysisDriver]s.
  final ByteStore _byteStore;

  /// The cache of deserialized data read from SummaryDataReader.
  ///
  /// It can be shared with other [AnalysisDriver]s.
  final InfoDeclarationStore _infoDeclarationStore;

  /// The optional store with externally provided unlinked and corresponding
  /// linked summaries. These summaries are always added to the store for any
  /// file analysis.
  final SummaryDataStore? _externalSummaries;

  /// This [ContentCache] is consulted for a file content before reading
  /// the content from the file.
  final FileContentCache _fileContentCache;

  /// The already loaded unlinked units,  consulted before deserializing
  /// from file again.
  final UnlinkedUnitStore _unlinkedUnitStore;

  late final StoredFileContentStrategy _fileContentStrategy;

  /// The analysis options to analyze with.
  final AnalysisOptionsImpl _analysisOptions;

  /// The [Packages] object with packages and their language versions.
  final Packages _packages;

  /// The [SourceFactory] is used to resolve URIs to paths and restore URIs
  /// from file paths.
  final SourceFactory _sourceFactory;

  final MacroKernelBuilder? macroKernelBuilder;

  /// The instance of macro executor that is used for all macros.
  final macro.MultiMacroExecutor? macroExecutor;

  /// The container, shared with other drivers within the same collection,
  /// into which all drivers record files ownership.
  final OwnedFiles? ownedFiles;

  /// The declared environment variables.
  final DeclaredVariables declaredVariables;

  /// The analysis context that created this driver / session.
  DriverBasedAnalysisContext? analysisContext;

  /// The salt to mix into all hashes used as keys for unlinked data.
  Uint32List _saltForUnlinked = Uint32List(0);

  /// The salt to mix into all hashes used as keys for elements.
  Uint32List _saltForElements = Uint32List(0);

  /// The salt to mix into all hashes used as keys for linked data.
  Uint32List _saltForResolution = Uint32List(0);

  /// The set of priority files, that should be analyzed sooner.
  final _priorityFiles = <String>{};

  /// The file changes that should be applied before processing requests.
  final List<_FileChange> _pendingFileChanges = [];

  /// When [_applyFileChangesSynchronously] is `true`, affected files are
  /// accumulated here.
  Set<String> _accumulatedAffected = {};

  /// The completers to complete after [_pendingFileChanges] are applied.
  final _pendingFileChangesCompleters = <Completer<List<String>>>[];

  /// The mapping from the files for which analysis was requested using
  /// [getResult] to the [Completer]s to report the result.
  final _requestedFiles = <String, List<Completer<SomeResolvedUnitResult>>>{};

  /// The mapping from the files for which analysis was requested using
  /// [getResolvedLibrary] to the [Completer]s to report the result.
  final _requestedLibraries =
      <LibraryFileKind, List<Completer<SomeResolvedLibraryResult>>>{};

  /// The queue of requests for completion.
  final List<_ResolveForCompletionRequest> _resolveForCompletionRequests = [];

  /// The task that discovers available files.  If this field is not `null`,
  /// and the task is not completed, it should be performed and completed
  /// before any name searching task.
  _DiscoverAvailableFilesTask? _discoverAvailableFilesTask;

  /// The list of tasks to compute files defining a class member name.
  final _definingClassMemberNameTasks = <_FilesDefiningClassMemberNameTask>[];

  /// The list of tasks to compute files referencing a name.
  final _referencingNameTasks = <_FilesReferencingNameTask>[];

  /// The mapping from the files for which errors were requested using
  /// [getErrors] to the [Completer]s to report the result.
  final _errorsRequestedFiles = <String, List<Completer<SomeErrorsResult>>>{};

  /// The mapping from the files for which the index was requested using
  /// [getIndex] to the [Completer]s to report the result.
  final _indexRequestedFiles =
      <String, List<Completer<AnalysisDriverUnitIndex?>>>{};

  /// The mapping from the files for which the unit element was requested using
  /// [getUnitElement] to the [Completer]s to report the result.
  final _unitElementRequestedFiles =
      <String, List<Completer<SomeUnitElementResult>>>{};

  /// The list of dispose requests, added in [dispose2], almost always empty.
  /// We expect that at most one is added, at the very end of the life cycle.
  final List<Completer<void>> _disposeRequests = [];

  /// The controller for the [results] stream.
  final _resultController = StreamController<Object>();

  /// The stream that will be written to when analysis results are produced.
  late final Stream<Object> _onResults;

  /// Resolution signatures of the most recently produced results for files.
  final Map<String, String> _lastProducedSignatures = {};

  /// Cached results for [_priorityFiles].
  final Map<String, ResolvedUnitResult> _priorityResults = {};

  /// Cached results of [getResolvedLibrary].
  final Map<LibraryFileKind, ResolvedLibraryResultImpl> _resolvedLibraryCache =
      {};

  /// The controller for the [exceptions] stream.
  final StreamController<ExceptionResult> _exceptionController =
      StreamController<ExceptionResult>();

  /// The instance of the [Search] helper.
  late final Search _search;

  final AnalysisDriverTestView? testView;

  late FeatureSetProvider featureSetProvider;

  late FileSystemState _fsState;

  /// The [FileTracker] used by this driver.
  late FileTracker _fileTracker;

  /// Whether resolved units should be indexed.
  final bool enableIndex;

  /// The context in which libraries should be analyzed.
  LibraryContext? _libraryContext;

  /// Whether `dart:core` has been transitively discovered.
  bool _hasDartCoreDiscovered = false;

  /// This flag is reset to `false` when a new file is added, because it
  /// might be a library, so that some files that were disconnected parts
  /// could be analyzed now.
  bool _hasLibrariesDiscovered = false;

  /// If testing data is being retained, a pointer to the object that is
  /// retaining the testing data.  Otherwise `null`.
  final TestingData? testingData;

  bool _disposed = false;

  /// Create a new instance of [AnalysisDriver].
  ///
  /// The given [SourceFactory] is cloned to ensure that it does not contain a
  /// reference to an [AnalysisContext] in which it could have been used.
  AnalysisDriver({
    required AnalysisDriverScheduler scheduler,
    required PerformanceLog logger,
    required ResourceProvider resourceProvider,
    required ByteStore byteStore,
    required SourceFactory sourceFactory,
    required AnalysisOptionsImpl analysisOptions,
    required Packages packages,
    this.macroKernelBuilder,
    this.macroExecutor,
    this.ownedFiles,
    this.analysisContext,
    FileContentCache? fileContentCache,
    UnlinkedUnitStore? unlinkedUnitStore,
    InfoDeclarationStore? infoDeclarationStore,
    this.enableIndex = false,
    SummaryDataStore? externalSummaries,
    DeclaredVariables? declaredVariables,
    bool retainDataForTesting = false,
    this.testView,
  })  : _scheduler = scheduler,
        _resourceProvider = resourceProvider,
        _byteStore = byteStore,
        _fileContentCache =
            fileContentCache ?? FileContentCache.ephemeral(resourceProvider),
        _unlinkedUnitStore = unlinkedUnitStore ?? UnlinkedUnitStoreImpl(),
        _infoDeclarationStore =
            infoDeclarationStore ?? NoOpInfoDeclarationStore(),
        _analysisOptions = analysisOptions,
        _logger = logger,
        _packages = packages,
        _sourceFactory = sourceFactory,
        _externalSummaries = externalSummaries,
        declaredVariables = declaredVariables ?? DeclaredVariables(),
        testingData = retainDataForTesting ? TestingData() : null {
    analysisContext?.driver = this;
    testView?.driver = this;
    _onResults = _resultController.stream.asBroadcastStream();

    _fileContentStrategy = StoredFileContentStrategy(_fileContentCache);

    _createFileTracker();
    _scheduler.add(this);
    _search = Search(this);
  }

  /// Return the set of files explicitly added to analysis using [addFile].
  Set<String> get addedFiles => _fileTracker.addedFiles;

  /// Return the analysis options used to control analysis.
  AnalysisOptions get analysisOptions => _analysisOptions;

  /// Return the current analysis session.
  AnalysisSessionImpl get currentSession {
    return libraryContext.elementFactory.analysisSession;
  }

  /// Return the stream that produces [ExceptionResult]s.
  Stream<ExceptionResult> get exceptions => _exceptionController.stream;

  /// The current file system state.
  FileSystemState get fsState => _fsState;

  @override
  bool get hasFilesToAnalyze {
    return hasPendingFileChanges ||
        _fileTracker.hasChangedFiles ||
        _requestedFiles.isNotEmpty ||
        _fileTracker.hasPendingFiles;
  }

  bool get hasPendingFileChanges => _pendingFileChanges.isNotEmpty;

  /// Return the set of files that are known at this moment. This set does not
  /// always include all added files or all implicitly used file. If a file has
  /// not been processed yet, it might be missing.
  Set<String> get knownFiles => _fsState.knownFilePaths;

  /// Return the context in which libraries should be analyzed.
  LibraryContext get libraryContext {
    return _libraryContext ??= LibraryContext(
      testData: testView?.libraryContext,
      analysisSession: AnalysisSessionImpl(this),
      logger: _logger,
      byteStore: _byteStore,
      infoDeclarationStore: _infoDeclarationStore,
      analysisOptions: _analysisOptions,
      declaredVariables: declaredVariables,
      sourceFactory: _sourceFactory,
      macroKernelBuilder: macroKernelBuilder,
      macroExecutor: macroExecutor,
      externalSummaries: _externalSummaries,
      fileSystemState: _fsState,
    );
  }

  /// Return the path of the folder at the root of the context.
  String get name => analysisContext?.contextRoot.root.path ?? '';

  /// Return the number of files scheduled for analysis.
  int get numberOfFilesToAnalyze => _fileTracker.numberOfPendingFiles;

  /// Return the list of files that the driver should try to analyze sooner.
  List<String> get priorityFiles => _priorityFiles.toList(growable: false);

  @override
  set priorityFiles(List<String> priorityPaths) {
    _priorityResults.keys
        .toSet()
        .difference(priorityPaths.toSet())
        .forEach(_priorityResults.remove);
    _priorityFiles.clear();
    _priorityFiles.addAll(priorityPaths);
    _scheduler.notify(this);
  }

  /// Return the [ResourceProvider] that is used to access the file system.
  ResourceProvider get resourceProvider => _resourceProvider;

  /// Return the [Stream] that produces [AnalysisResult]s for added files.
  ///
  /// Note that the stream supports only one single subscriber.
  ///
  /// Analysis starts when the [AnalysisDriverScheduler] is started and the
  /// driver is added to it. The analysis state transitions to "analyzing" and
  /// an analysis result is produced for every added file prior to the next time
  /// the analysis state transitions to "idle".
  ///
  /// [ResolvedUnitResult]s are produced for:
  /// 1. Files requested using [getResult].
  /// 2. Files passed to [addFile] which are also in [priorityFiles].
  ///
  /// [ErrorsResult]s are produced for:
  /// 1. Files passed to [addFile] which are not in [priorityFiles].
  ///
  /// At least one analysis result is produced for every file passed to
  /// [addFile] or [changeFile] prior to the next time the analysis state
  /// transitions to "idle", unless the file is later removed from analysis
  /// using [removeFile]. Analysis results for other files are produced only if
  /// the changes affect analysis results of other files.
  ///
  /// More than one result might be produced for the same file, even if the
  /// client does not change the state of the files.
  ///
  /// Results might be produced even for files that have never been added
  /// using [addFile], for example when [getResult] was called for a file.
  Stream<Object> get results => _onResults;

  /// Return the search support for the driver.
  Search get search => _search;

  /// Return the source factory used to resolve URIs to paths and restore URIs
  /// from file paths.
  SourceFactory get sourceFactory => _sourceFactory;

  @override
  AnalysisDriverPriority get workPriority {
    if (_disposeRequests.isNotEmpty) {
      return AnalysisDriverPriority.interactive;
    }
    if (_resolveForCompletionRequests.isNotEmpty) {
      return AnalysisDriverPriority.completion;
    }
    if (_requestedFiles.isNotEmpty) {
      return AnalysisDriverPriority.interactive;
    }
    if (_requestedLibraries.isNotEmpty) {
      return AnalysisDriverPriority.interactive;
    }
    if (_discoverAvailableFilesTask != null &&
        !_discoverAvailableFilesTask!.isCompleted) {
      return AnalysisDriverPriority.interactive;
    }
    if (_definingClassMemberNameTasks.isNotEmpty ||
        _referencingNameTasks.isNotEmpty) {
      return AnalysisDriverPriority.interactive;
    }
    if (_errorsRequestedFiles.isNotEmpty) {
      return AnalysisDriverPriority.interactive;
    }
    if (_indexRequestedFiles.isNotEmpty) {
      return AnalysisDriverPriority.interactive;
    }
    if (_unitElementRequestedFiles.isNotEmpty) {
      return AnalysisDriverPriority.interactive;
    }
    if (_priorityFiles.isNotEmpty) {
      for (String path in _priorityFiles) {
        if (_fileTracker.isFilePending(path)) {
          return AnalysisDriverPriority.priority;
        }
      }
    }
    if (_pendingFileChanges.isNotEmpty) {
      return AnalysisDriverPriority.general;
    }
    if (_fileTracker.hasChangedFiles) {
      return AnalysisDriverPriority.changedFiles;
    }
    if (_fileTracker.hasPendingChangedFiles) {
      return AnalysisDriverPriority.generalChanged;
    }
    if (_fileTracker.hasPendingImportFiles) {
      return AnalysisDriverPriority.generalImportChanged;
    }
    if (_fileTracker.hasPendingErrorFiles) {
      return AnalysisDriverPriority.generalWithErrors;
    }
    if (_fileTracker.hasPendingFiles) {
      return AnalysisDriverPriority.general;
    }
    if (_pendingFileChangesCompleters.isNotEmpty) {
      return AnalysisDriverPriority.general;
    }
    return AnalysisDriverPriority.nothing;
  }

  @override
  void addFile(String path) {
    _throwIfNotAbsolutePath(path);
    if (!_fsState.hasUri(path)) {
      return;
    }
    if (file_paths.isDart(resourceProvider.pathContext, path)) {
      _priorityResults.clear();
      _resolvedLibraryCache.clear();
      _pendingFileChanges.add(
        _FileChange(path, _FileChangeKind.add),
      );
      _scheduler.notify(this);
    }
  }

  /// Return a [Future] that completes after pending file changes are applied,
  /// so that [currentSession] can be used to compute results.
  ///
  /// The value is the set of all files that are potentially affected by
  /// the pending changes. This set can be both wider than the set of analyzed
  /// files (because it may include files imported from other packages, and
  /// which are on the import path from a changed file to an analyze file),
  /// and narrower than the set of analyzed files (because only files that
  /// were previously accessed are considered to be known and affected).
  Future<List<String>> applyPendingFileChanges() {
    if (_pendingFileChanges.isNotEmpty) {
      if (_disposed) throw DisposedAnalysisContextResult();
      var completer = Completer<List<String>>();
      _pendingFileChangesCompleters.add(completer);
      return completer.future;
    } else {
      var accumulatedAffected = _accumulatedAffected.toList();
      _accumulatedAffected = {};
      return Future.value(accumulatedAffected);
    }
  }

  /// Builds elements for library files from [uriList], and packs them into
  /// a bundle suitable for [PackageBundleReader].
  ///
  /// Disconnected non-library files are ignored.
  Future<Uint8List> buildPackageBundle({
    required List<Uri> uriList,
    PackageBundleSdk? packageBundleSdk,
  }) async {
    final elementFactory = libraryContext.elementFactory;

    final bundleWriter = BundleWriter(
      elementFactory.dynamicRef,
    );
    final packageBundleBuilder = PackageBundleBuilder();

    for (final uri in uriList) {
      final uriStr = uri.toString();
      final libraryResult = await getLibraryByUri(uriStr);
      if (libraryResult is LibraryElementResult) {
        final libraryElement = libraryResult.element as LibraryElementImpl;
        bundleWriter.writeLibraryElement(libraryElement);

        packageBundleBuilder.addLibrary(
          uriStr,
          libraryElement.units.map((e) {
            return e.source.uri.toString();
          }).toList(),
        );
      }
    }

    final writeWriterResult = bundleWriter.finish();

    return packageBundleBuilder.finish(
      resolutionBytes: writeWriterResult.resolutionBytes,
      sdk: packageBundleSdk,
    );
  }

  /// The file with the given [path] might have changed - updated, added or
  /// removed. Or not, we don't know. Or it might have, but then changed back.
  ///
  /// The [path] must be absolute and normalized.
  ///
  /// The [path] can be any file - explicitly or implicitly analyzed, or neither.
  ///
  /// Causes the analysis state to transition to "analyzing" (if it is not in
  /// that state already). Schedules the file contents for [path] to be read
  /// into the current file state prior to the next time the analysis state
  /// transitions to "idle".
  ///
  /// Invocation of this method will not prevent a [Future] returned from
  /// [getResult] from completing with a result, but the result is not
  /// guaranteed to be consistent with the new current file state after this
  /// [changeFile] invocation.
  void changeFile(String path) {
    _throwIfNotAbsolutePath(path);
    if (!_fsState.hasUri(path)) {
      return;
    }
    if (file_paths.isDart(resourceProvider.pathContext, path)) {
      _priorityResults.clear();
      _resolvedLibraryCache.clear();
      _pendingFileChanges.add(
        _FileChange(path, _FileChangeKind.change),
      );
      _scheduler.notify(this);
    }
  }

  /// Clear the library context and any related data structures. Mostly we do
  /// this to reduce memory consumption. The library context holds to every
  /// library that was resynthesized, but after some initial analysis we might
  /// not get again to many of these libraries. So, we should clear the context
  /// periodically.
  void clearLibraryContext() {
    _libraryContext?.dispose();
    _libraryContext = null;
  }

  /// Return a [Future] that completes when discovery of all files that are
  /// potentially available is done, so that they are included in [knownFiles].
  Future<void> discoverAvailableFiles() {
    if (_discoverAvailableFilesTask != null &&
        _discoverAvailableFilesTask!.isCompleted) {
      return Future.value();
    }
    _discoverAvailableFiles();
    _scheduler.notify(this);
    return _discoverAvailableFilesTask!.completer.future;
  }

  @override
  Future<void> dispose2() async {
    final completer = Completer<void>();
    _disposed = true;
    _disposeRequests.add(completer);

    // Complete all waiting completers.
    for (var completerList in _requestedLibraries.values) {
      for (var completer in completerList) {
        completer.complete(DisposedAnalysisContextResult());
      }
    }
    _requestedLibraries.clear();

    for (var completerList in _requestedFiles.values) {
      for (var completer in completerList) {
        completer.complete(DisposedAnalysisContextResult());
      }
    }
    _requestedFiles.clear();

    for (var completerList in _unitElementRequestedFiles.values) {
      for (var completer in completerList) {
        completer.complete(DisposedAnalysisContextResult());
      }
    }
    _unitElementRequestedFiles.clear();

    for (var completerList in _errorsRequestedFiles.values) {
      for (var completer in completerList) {
        completer.complete(DisposedAnalysisContextResult());
      }
    }
    _errorsRequestedFiles.clear();

    for (var completer in _pendingFileChangesCompleters) {
      completer.completeError(DisposedAnalysisContextResult());
    }
    _pendingFileChangesCompleters.clear();

    _scheduler.notify(this);
    return completer.future;
  }

  /// Return the cached [ResolvedUnitResult] for the Dart file with the given
  /// [path]. If there is no cached result, return `null`. Usually only results
  /// of priority files are cached.
  ///
  /// The [path] must be absolute and normalized.
  ///
  /// The [path] can be any file - explicitly or implicitly analyzed, or neither.
  ResolvedUnitResult? getCachedResult(String path) {
    _throwIfNotAbsolutePath(path);
    return _priorityResults[path];
  }

  /// Return a [Future] that completes with the [ErrorsResult] for the Dart
  /// file with the given [path].
  ///
  /// The [path] must be absolute and normalized.
  ///
  /// This method does not use analysis priorities, and must not be used in
  /// interactive analysis, such as Analysis Server or its plugins.
  Future<SomeErrorsResult> getErrors(String path) async {
    if (!_isAbsolutePath(path)) {
      return Future.value(
        InvalidPathResult(),
      );
    }

    if (!_fsState.hasUri(path)) {
      return Future.value(
        NotPathOfUriResult(),
      );
    }

    if (_disposed) {
      return Future.value(
        DisposedAnalysisContextResult(),
      );
    }

    var completer = Completer<SomeErrorsResult>();
    _errorsRequestedFiles.putIfAbsent(path, () => []).add(completer);
    _scheduler.notify(this);
    return completer.future;
  }

  /// Return a [Future] that completes with the list of added files that
  /// define a class member with the given [name].
  Future<List<String>> getFilesDefiningClassMemberName(String name) {
    _discoverAvailableFiles();
    var task = _FilesDefiningClassMemberNameTask(this, name);
    _definingClassMemberNameTasks.add(task);
    _scheduler.notify(this);
    return task.completer.future;
  }

  /// Return a [Future] that completes with the list of known files that
  /// reference the given external [name].
  Future<List<String>> getFilesReferencingName(String name) {
    _discoverAvailableFiles();
    var task = _FilesReferencingNameTask(this, name);
    _referencingNameTasks.add(task);
    _scheduler.notify(this);
    return task.completer.future;
  }

  /// Return the [FileResult] for the Dart file with the given [path].
  ///
  /// The [path] must be absolute and normalized.
  SomeFileResult getFileSync(String path) {
    if (!_isAbsolutePath(path)) {
      return InvalidPathResult();
    }

    FileState file = _fsState.getFileForPath(path);
    return FileResultImpl(
      session: currentSession,
      path: path,
      uri: file.uri,
      lineInfo: file.lineInfo,
      isAugmentation: file.kind is AugmentationFileKind,
      isLibrary: file.kind is LibraryFileKind,
      isPart: file.kind is PartFileKind,
    );
  }

  /// Return a [Future] that completes with the [AnalysisDriverUnitIndex] for
  /// the file with the given [path], or with `null` if the file cannot be
  /// analyzed.
  Future<AnalysisDriverUnitIndex?> getIndex(String path) {
    _throwIfNotAbsolutePath(path);
    if (!enableIndex) {
      throw ArgumentError('Indexing is not enabled.');
    }
    if (!_fsState.hasUri(path)) {
      return Future.value();
    }
    var completer = Completer<AnalysisDriverUnitIndex?>();
    _indexRequestedFiles.putIfAbsent(path, () => []).add(completer);
    _scheduler.notify(this);
    return completer.future;
  }

  /// Return a [Future] that completes with [LibraryElementResult] for the given
  /// [uri], which is either resynthesized from the provided external summary
  /// store, or built for a file to which the given [uri] is resolved.
  Future<SomeLibraryElementResult> getLibraryByUri(String uri) async {
    var uriObj = uriCache.parse(uri);

    // Check if the element is already computed.
    if (_pendingFileChanges.isEmpty) {
      final rootReference = libraryContext.elementFactory.rootReference;
      final reference = rootReference.getChild('$uriObj');
      final element = reference.element;
      if (element is LibraryElementImpl) {
        return LibraryElementResultImpl(element);
      }
    }

    var fileOr = _fsState.getFileForUri(uriObj);
    switch (fileOr) {
      case null:
        return CannotResolveUriResult();
      case UriResolutionFile(:final file):
        final kind = file.kind;
        if (kind is LibraryFileKind) {
        } else if (kind is AugmentationFileKind) {
          return NotLibraryButAugmentationResult();
        } else if (kind is PartFileKind) {
          return NotLibraryButPartResult();
        } else {
          throw UnimplementedError('(${kind.runtimeType}) $kind');
        }

        var unitResult = await getUnitElement(file.path);
        if (unitResult is UnitElementResult) {
          return LibraryElementResultImpl(unitResult.element.library);
        }

        // Some invalid results are invalid results for this request.
        // Note that up-down promotion does not work.
        if (unitResult is InvalidResult &&
            unitResult is SomeLibraryElementResult) {
          return unitResult as SomeLibraryElementResult;
        }

        // Should not happen.
        return UnspecifiedInvalidResult();
      case UriResolutionExternalLibrary(:final source):
        final uri = source.uri;
        // TODO(scheglov) Check if the source is not for library.
        var element = libraryContext.getLibraryElement(uri);
        return LibraryElementResultImpl(element);
    }
  }

  /// Return a [ParsedLibraryResult] for the library with the given [path].
  ///
  /// The [path] must be absolute and normalized.
  SomeParsedLibraryResult getParsedLibrary(String path) {
    if (!_isAbsolutePath(path)) {
      return InvalidPathResult();
    }

    if (!_fsState.hasUri(path)) {
      return NotPathOfUriResult();
    }

    final file = _fsState.getFileForPath(path);
    final kind = file.kind;
    if (kind is LibraryFileKind) {
    } else if (kind is AugmentationFileKind) {
      return NotLibraryButAugmentationResult();
    } else if (kind is PartFileKind) {
      return NotLibraryButPartResult();
    } else {
      throw UnimplementedError('(${kind.runtimeType}) $kind');
    }

    var units = <ParsedUnitResult>[];
    for (var unitFile in kind.files) {
      var unitPath = unitFile.path;
      var unitResult = parseFileSync(unitPath);
      if (unitResult is! ParsedUnitResult) {
        return UnspecifiedInvalidResult();
      }
      units.add(unitResult);
    }

    return ParsedLibraryResultImpl(
      session: currentSession,
      units: units,
    );
  }

  /// Return a [ParsedLibraryResult] for the library with the given [uri].
  SomeParsedLibraryResult getParsedLibraryByUri(Uri uri) {
    var fileOr = _fsState.getFileForUri(uri);
    switch (fileOr) {
      case null:
        return CannotResolveUriResult();
      case UriResolutionFile(:final file):
        return getParsedLibrary(file.path);
      case UriResolutionExternalLibrary():
        return UriOfExternalLibraryResult();
    }
  }

  /// Return a [Future] that completes with a [ResolvedLibraryResult] for the
  /// Dart library file with the given [path].  If the file cannot be analyzed,
  /// the [Future] completes with an [InvalidResult].
  ///
  /// The [path] must be absolute and normalized.
  ///
  /// The [path] can be any file - explicitly or implicitly analyzed, or neither.
  ///
  /// Invocation of this method causes the analysis state to transition to
  /// "analyzing" (if it is not in that state already), the driver will produce
  /// the resolution result for it, which is consistent with the current file
  /// state (including new states of the files previously reported using
  /// [changeFile]), prior to the next time the analysis state transitions
  /// to "idle".
  Future<SomeResolvedLibraryResult> getResolvedLibrary(String path) async {
    if (!_isAbsolutePath(path)) {
      return InvalidPathResult();
    }

    if (!_fsState.hasUri(path)) {
      return NotPathOfUriResult();
    }

    if (_disposed) {
      return Future.value(
        DisposedAnalysisContextResult(),
      );
    }

    final file = _fsState.getFileForPath(path);
    final kind = file.kind;
    if (kind is LibraryFileKind) {
      final completer = Completer<SomeResolvedLibraryResult>();
      _requestedLibraries.putIfAbsent(kind, () => []).add(completer);
      _scheduler.notify(this);
      return completer.future;
    } else if (kind is AugmentationFileKind) {
      return NotLibraryButAugmentationResult();
    } else if (kind is PartFileKind) {
      return NotLibraryButPartResult();
    } else {
      throw UnimplementedError('(${kind.runtimeType}) $kind');
    }
  }

  /// Return a [Future] that completes with a [ResolvedLibraryResult] for the
  /// Dart library file with the given [uri].  If the file cannot be analyzed,
  /// the [Future] completes with an [InvalidResult].
  ///
  /// Invocation of this method causes the analysis state to transition to
  /// "analyzing" (if it is not in that state already), the driver will produce
  /// the resolution result for it, which is consistent with the current file
  /// state (including new states of the files previously reported using
  /// [changeFile]), prior to the next time the analysis state transitions
  /// to "idle".
  Future<SomeResolvedLibraryResult> getResolvedLibraryByUri(Uri uri) async {
    var fileOr = _fsState.getFileForUri(uri);
    switch (fileOr) {
      case null:
        return CannotResolveUriResult();
      case UriResolutionFile(:final file):
        return getResolvedLibrary(file.path);
      case UriResolutionExternalLibrary():
        return UriOfExternalLibraryResult();
    }
  }

  /// Return a [Future] that completes with a [SomeResolvedUnitResult] for the
  /// Dart file with the given [path].  If the file cannot be analyzed,
  /// the [Future] completes with an [InvalidResult].
  ///
  /// The [path] must be absolute and normalized.
  ///
  /// The [path] can be any file - explicitly or implicitly analyzed, or neither.
  ///
  /// If the driver has the cached analysis result for the file, it is returned.
  /// If [sendCachedToStream] is `true`, then the result is also reported into
  /// the [results] stream, just as if it were freshly computed.
  ///
  /// Otherwise causes the analysis state to transition to "analyzing" (if it is
  /// not in that state already), the driver will produce the analysis result for
  /// it, which is consistent with the current file state (including new states
  /// of the files previously reported using [changeFile]), prior to the next
  /// time the analysis state transitions to "idle".
  Future<SomeResolvedUnitResult> getResult(String path,
      {bool sendCachedToStream = false}) {
    if (!_isAbsolutePath(path)) {
      return Future.value(
        InvalidPathResult(),
      );
    }

    if (!_fsState.hasUri(path)) {
      return Future.value(
        NotPathOfUriResult(),
      );
    }

    // Return the cached result.
    {
      ResolvedUnitResult? result = getCachedResult(path);
      if (result != null) {
        if (sendCachedToStream) {
          _resultController.add(result);
        }
        return Future.value(result);
      }
    }

    if (_disposed) {
      return Future.value(
        DisposedAnalysisContextResult(),
      );
    }

    // Schedule analysis.
    var completer = Completer<SomeResolvedUnitResult>();
    _requestedFiles.putIfAbsent(path, () => []).add(completer);
    _scheduler.notify(this);
    return completer.future;
  }

  /// Return a [Future] that completes with the [SomeUnitElementResult]
  /// for the file with the given [path].
  Future<SomeUnitElementResult> getUnitElement(String path) {
    if (!_isAbsolutePath(path)) {
      return Future.value(
        InvalidPathResult(),
      );
    }

    if (!_fsState.hasUri(path)) {
      return Future.value(
        NotPathOfUriResult(),
      );
    }

    if (_disposed) {
      return Future.value(
        DisposedAnalysisContextResult(),
      );
    }

    var completer = Completer<SomeUnitElementResult>();
    _unitElementRequestedFiles.putIfAbsent(path, () => []).add(completer);
    _scheduler.notify(this);
    return completer.future;
  }

  /// Return a [ParsedUnitResult] for the file with the given [path].
  ///
  /// The [path] must be absolute and normalized.
  ///
  /// The [path] can be any file - explicitly or implicitly analyzed, or neither.
  ///
  /// The parsing is performed in the method itself, and the result is not
  /// produced through the [results] stream (just because it is not a fully
  /// resolved unit).
  SomeParsedUnitResult parseFileSync(String path) {
    if (!_isAbsolutePath(path)) {
      return InvalidPathResult();
    }

    FileState file = _fsState.getFileForPath(path);
    RecordingErrorListener listener = RecordingErrorListener();
    CompilationUnit unit = file.parse(listener);
    return ParsedUnitResultImpl(
      session: currentSession,
      path: file.path,
      uri: file.uri,
      content: file.content,
      lineInfo: file.lineInfo,
      isAugmentation: file.kind is AugmentationFileKind,
      isLibrary: file.kind is LibraryFileKind,
      isPart: file.kind is PartFileKind,
      unit: unit,
      errors: listener.errors,
    );
  }

  @override
  Future<void> performWork() async {
    _discoverDartCore();
    _discoverLibraries();

    if (_resolveForCompletionRequests.isNotEmpty) {
      final request = _resolveForCompletionRequests.removeLast();
      try {
        final result = await _resolveForCompletion(request);
        request.completer.complete(result);
      } catch (exception, stackTrace) {
        _reportException(request.path, exception, stackTrace);
        request.completer.completeError(exception, stackTrace);
        _clearLibraryContextAfterException();
      }
      return;
    }

    // Analyze a requested file.
    if (_requestedFiles.isNotEmpty) {
      final path = _requestedFiles.keys.first;
      final completers = _requestedFiles.remove(path)!;
      _fileTracker.fileWasAnalyzed(path);
      try {
        final result = await _computeAnalysisResult(path, withUnit: true);
        final unitResult = result.unitResult!;
        for (final completer in completers) {
          completer.complete(unitResult);
        }
        _resultController.add(unitResult);
      } catch (exception, stackTrace) {
        _reportException(path, exception, stackTrace);
        for (final completer in completers) {
          completer.completeError(exception, stackTrace);
        }
        _clearLibraryContextAfterException();
      }
      return;
    }

    // Analyze a requested library.
    if (_requestedLibraries.isNotEmpty) {
      final library = _requestedLibraries.keys.first;
      try {
        var result = await _computeResolvedLibrary(library);
        for (var completer in _requestedLibraries.remove(library)!) {
          completer.complete(result);
        }
      } catch (exception, stackTrace) {
        for (var completer in _requestedLibraries.remove(library)!) {
          completer.completeError(exception, stackTrace);
        }
        _clearLibraryContextAfterException();
      }
      return;
    }

    // Process an error request.
    if (_errorsRequestedFiles.isNotEmpty) {
      var path = _errorsRequestedFiles.keys.first;
      var completers = _errorsRequestedFiles.remove(path)!;
      var result = await _computeErrors(
        path: path,
      );
      for (var completer in completers) {
        completer.complete(result);
      }
      return;
    }

    // Process an index request.
    if (_indexRequestedFiles.isNotEmpty) {
      String path = _indexRequestedFiles.keys.first;
      final index = await _computeIndex(path);
      for (var completer in _indexRequestedFiles.remove(path)!) {
        completer.complete(index);
      }
      return;
    }

    // Process a unit element request.
    if (_unitElementRequestedFiles.isNotEmpty) {
      String path = _unitElementRequestedFiles.keys.first;
      var completers = _unitElementRequestedFiles.remove(path)!;
      final result = (await _computeUnitElement(path))!;
      for (var completer in completers) {
        completer.complete(result);
      }
      return;
    }

    // Discover available files.
    if (_discoverAvailableFilesTask != null &&
        !_discoverAvailableFilesTask!.isCompleted) {
      _discoverAvailableFilesTask!.perform();
      return;
    }

    // Compute files defining a name.
    if (_definingClassMemberNameTasks.isNotEmpty) {
      _FilesDefiningClassMemberNameTask task =
          _definingClassMemberNameTasks.first;
      bool isDone = task.perform();
      if (isDone) {
        _definingClassMemberNameTasks.remove(task);
      }
      return;
    }

    // Compute files referencing a name.
    if (_referencingNameTasks.isNotEmpty) {
      _FilesReferencingNameTask task = _referencingNameTasks.first;
      bool isDone = task.perform();
      if (isDone) {
        _referencingNameTasks.remove(task);
      }
      return;
    }

    // Analyze a priority file.
    if (_priorityFiles.isNotEmpty) {
      for (String path in _priorityFiles) {
        if (_fileTracker.isFilePending(path)) {
          try {
            var result = await _computeAnalysisResult(path, withUnit: true);
            _resultController.add(result.unitResult!);
          } catch (exception, stackTrace) {
            _reportException(path, exception, stackTrace);
            _clearLibraryContextAfterException();
          } finally {
            _fileTracker.fileWasAnalyzed(path);
          }
          return;
        }
      }
    }

    // Analyze a general file.
    if (_fileTracker.hasPendingFiles) {
      String path = _fileTracker.anyPendingFile;
      try {
        var result = await _computeAnalysisResult(path,
            withUnit: false, skipIfSameSignature: true);
        if (result.isUnchangedErrors) {
          // We found that the set of errors is the same as we produced the
          // last time, so we don't need to produce it again now.
        } else {
          _resultController.add(result.errorsResult!);
          _lastProducedSignatures[path] = result._signature;
        }
      } catch (exception, stackTrace) {
        _reportException(path, exception, stackTrace);
        _clearLibraryContextAfterException();
      } finally {
        _fileTracker.fileWasAnalyzed(path);
      }
      return;
    }
  }

  /// Remove the file with the given [path] from the list of files to analyze.
  ///
  /// The [path] must be absolute and normalized.
  ///
  /// The results of analysis of the file might still be produced by the
  /// [results] stream. The driver will try to stop producing these results,
  /// but does not guarantee this.
  void removeFile(String path) {
    _throwIfNotAbsolutePath(path);
    if (!_fsState.hasUri(path)) {
      return;
    }
    if (file_paths.isDart(resourceProvider.pathContext, path)) {
      _lastProducedSignatures.remove(path);
      _priorityResults.clear();
      _resolvedLibraryCache.clear();
      _pendingFileChanges.add(
        _FileChange(path, _FileChangeKind.remove),
      );
      _scheduler.notify(this);
    }
  }

  Future<ResolvedForCompletionResultImpl?> resolveForCompletion({
    required String path,
    required int offset,
    required OperationPerformanceImpl performance,
  }) async {
    final request = _ResolveForCompletionRequest(
      path: path,
      offset: offset,
      performance: performance,
    );
    _resolveForCompletionRequests.add(request);
    _scheduler.notify(this);
    return request.completer.future;
  }

  void _addDeclaredVariablesToSignature(ApiSignature buffer) {
    var variableNames = declaredVariables.variableNames;
    buffer.addInt(variableNames.length);

    for (var name in variableNames) {
      var value = declaredVariables.get(name);
      buffer.addString(name);
      buffer.addString(value!);
    }
  }

  void _applyPendingFileChanges() {
    var accumulatedAffected = <String>{};
    for (var fileChange in _pendingFileChanges) {
      var path = fileChange.path;
      _removePotentiallyAffectedLibraries(accumulatedAffected, path);
      switch (fileChange.kind) {
        case _FileChangeKind.add:
          _fileTracker.addFile(path);
          break;
        case _FileChangeKind.change:
          _fileTracker.changeFile(path);
          break;
        case _FileChangeKind.remove:
          _fileTracker.removeFile(path);
          // TODO(scheglov) We have to do this because we discard files.
          // But this is not right, we need to handle removing better.
          clearLibraryContext();
          break;
      }
    }
    _pendingFileChanges.clear();

    // Read files, so that synchronous methods also see new content.
    while (_fileTracker.verifyChangedFilesIfNeeded()) {}

    if (_pendingFileChangesCompleters.isNotEmpty) {
      var completers = _pendingFileChangesCompleters.toList();
      _pendingFileChangesCompleters.clear();
      for (var completer in completers) {
        completer.complete(
          accumulatedAffected.toList(),
        );
      }
    }
  }

  /// There was an exception during a file analysis, we don't know why.
  /// But it might have been caused by an inconsistency of files state, and
  /// the library context state. Reset the library context, and hope that
  /// we will solve the inconsistency while loading / building summaries.
  void _clearLibraryContextAfterException() {
    clearLibraryContext();
  }

  /// Return the cached or newly computed analysis result of the file with the
  /// given [path].
  ///
  /// The [withUnit] flag control which result will be returned.
  /// When `true`, [AnalysisResult.unitResult] will be set.
  /// Otherwise [AnalysisResult.errorsResult] will be set.
  ///
  /// Return [AnalysisResult._UNCHANGED] if [skipIfSameSignature] is `true` and
  /// the resolved signature of the file in its library is the same as the one
  /// that was the most recently produced to the client.
  Future<AnalysisResult> _computeAnalysisResult(String path,
      {required bool withUnit, bool skipIfSameSignature = false}) async {
    FileState file = _fsState.getFileForPath(path);

    // Prepare the library - the file itself, or the known library.
    final kind = file.kind;
    final library = kind.library ?? kind.asLibrary;

    // Prepare the signature and key.
    String signature = _getResolvedUnitSignature(library, file);
    String key = _getResolvedUnitKey(signature);

    // Skip reading if the signature, so errors, are the same as the last time.
    if (skipIfSameSignature) {
      assert(!withUnit);
      if (_lastProducedSignatures[path] == signature) {
        return AnalysisResult.unchangedErrors(signature);
      }
    }

    // If we don't need the fully resolved unit, check for the cached result.
    if (!withUnit) {
      var bytes = _byteStore.get(key);
      if (bytes != null) {
        return _getAnalysisResultFromBytes(file, signature, bytes);
      }
    }

    // We need the fully resolved unit, or the result is not cached.
    return _logger.runAsync('Compute analysis result for $path', () async {
      _logger.writeln('Work in $name');
      try {
        testView?.numOfAnalyzedLibraries++;

        if (!_hasLibraryByUri('dart:core')) {
          return _newMissingDartLibraryResult(file, 'dart:core');
        }

        if (!_hasLibraryByUri('dart:async')) {
          return _newMissingDartLibraryResult(file, 'dart:async');
        }

        await libraryContext.load(
          targetLibrary: library,
          performance: OperationPerformanceImpl('<root>'),
        );

        var results = LibraryAnalyzer(
          analysisOptions as AnalysisOptionsImpl,
          declaredVariables,
          libraryContext.elementFactory.libraryOfUri2(library.file.uri),
          libraryContext.elementFactory.analysisSession.inheritanceManager,
          library,
          resourceProvider.pathContext,
          testingData: testingData,
        ).analyze();

        final isLibraryWithPriorityFile = _isLibraryWithPriorityFile(library);

        late AnalysisResult result;
        final resolvedUnits = <ResolvedUnitResultImpl>[];
        for (var unitResult in results) {
          var unitFile = unitResult.file;

          final index = enableIndex
              ? indexUnit(unitResult.unit)
              : AnalysisDriverUnitIndexBuilder();

          final unitBytes = AnalysisDriverResolvedUnitBuilder(
            errors: unitResult.errors.map((error) {
              return ErrorEncoding.encode(error);
            }).toList(),
            index: index,
          ).toBuffer();

          final resolvedUnit = _createResolvedUnitImpl(
            file: unitFile,
            unitResult: unitResult,
          );
          resolvedUnits.add(resolvedUnit);

          if (isLibraryWithPriorityFile) {
            _priorityResults[unitFile.path] = resolvedUnit;
          }

          String unitSignature = _getResolvedUnitSignature(library, unitFile);
          String unitKey = _getResolvedUnitKey(unitSignature);
          _byteStore.putGet(unitKey, unitBytes);

          _updateHasErrorOrWarningFlag(file, resolvedUnit.errors);

          if (unitFile == file) {
            if (withUnit) {
              result = AnalysisResult.unit(signature, resolvedUnit, index);
            } else {
              result = AnalysisResult.errors(
                signature,
                _createErrorsResultImpl(
                  file: unitFile,
                  errors: unitResult.errors,
                ),
                index,
              );
            }
          }
        }

        if (isLibraryWithPriorityFile) {
          final libraryResult = ResolvedLibraryResultImpl(
            session: currentSession,
            element: resolvedUnits.first.libraryElement,
            units: resolvedUnits,
          );
          _resolvedLibraryCache[library] = libraryResult;
        }

        // Return the result, full or partial.
        _logger.writeln('Computed new analysis result.');
        return result;
      } catch (exception, stackTrace) {
        String? contextKey =
            _storeExceptionContext(path, library, exception, stackTrace);
        throw _ExceptionState(exception, stackTrace, contextKey);
      }
    });
  }

  Future<SomeErrorsResult> _computeErrors({
    required String path,
  }) async {
    var analysisResult = await _computeAnalysisResult(path, withUnit: false);
    return analysisResult.errorsResult!;
  }

  Future<AnalysisDriverUnitIndex> _computeIndex(String path) async {
    var analysisResult = await _computeAnalysisResult(path, withUnit: false);
    return analysisResult._index!;
  }

  /// Return the newly computed resolution result of the library with the
  /// given [path].
  Future<ResolvedLibraryResultImpl> _computeResolvedLibrary(
    LibraryFileKind library,
  ) async {
    final cached = _resolvedLibraryCache[library];
    if (cached != null) {
      return cached;
    }

    final path = library.file.path;
    return _logger.runAsync('Compute resolved library $path', () async {
      testView?.numOfAnalyzedLibraries++;
      await libraryContext.load(
        targetLibrary: library,
        performance: OperationPerformanceImpl('<root>'),
      );

      var unitResults = LibraryAnalyzer(
              analysisOptions as AnalysisOptionsImpl,
              declaredVariables,
              libraryContext.elementFactory.libraryOfUri2(library.file.uri),
              libraryContext.elementFactory.analysisSession.inheritanceManager,
              library,
              resourceProvider.pathContext,
              testingData: testingData)
          .analyze();
      var resolvedUnits = <ResolvedUnitResult>[];

      final isLibraryWithPriorityFile = _isLibraryWithPriorityFile(library);
      for (final unitResult in unitResults) {
        final unitFile = unitResult.file;
        final resolvedUnit = _createResolvedUnitImpl(
          file: unitFile,
          unitResult: unitResult,
        );
        resolvedUnits.add(resolvedUnit);
        if (isLibraryWithPriorityFile) {
          _priorityResults[unitFile.path] = resolvedUnit;
        }
      }

      final result = ResolvedLibraryResultImpl(
        session: currentSession,
        element: resolvedUnits.first.libraryElement,
        units: resolvedUnits,
      );

      if (isLibraryWithPriorityFile) {
        _resolvedLibraryCache[library] = result;
      }

      return result;
    });
  }

  Future<UnitElementResult?> _computeUnitElement(String path) async {
    FileState file = _fsState.getFileForPath(path);

    // Prepare the library - the file itself, or the known library.
    final kind = file.kind;
    final library = kind.library ?? kind.asLibrary;

    return _logger.runAsync('Compute unit element for $path', () async {
      _logger.writeln('Work in $name');
      await libraryContext.load(
        targetLibrary: library,
        performance: OperationPerformanceImpl('<root>'),
      );
      var element = libraryContext.computeUnitElement(library, file);
      return UnitElementResultImpl(
        session: currentSession,
        path: path,
        uri: file.uri,
        lineInfo: file.lineInfo,
        isAugmentation: file.kind is AugmentationFileKind,
        isLibrary: file.kind is LibraryFileKind,
        isPart: file.kind is PartFileKind,
        element: element,
      );
    });
  }

  ErrorsResultImpl _createErrorsResultImpl({
    required FileState file,
    required List<AnalysisError> errors,
  }) {
    return ErrorsResultImpl(
      session: currentSession,
      path: file.path,
      uri: file.uri,
      lineInfo: file.lineInfo,
      isAugmentation: file.kind is AugmentationFileKind,
      isLibrary: file.kind is LibraryFileKind,
      isPart: file.kind is PartFileKind,
      errors: errors,
    );
  }

  /// Creates new [FileSystemState] and [FileTracker] objects.
  ///
  /// This is used both on initial construction and whenever the configuration
  /// changes.
  void _createFileTracker() {
    _fillSalt();

    featureSetProvider = FeatureSetProvider.build(
      sourceFactory: sourceFactory,
      resourceProvider: _resourceProvider,
      packages: _packages,
      packageDefaultFeatureSet: _analysisOptions.contextFeatures,
      nonPackageDefaultLanguageVersion:
          _analysisOptions.nonPackageLanguageVersion,
      nonPackageDefaultFeatureSet: _analysisOptions.nonPackageFeatureSet,
    );

    _fsState = FileSystemState(
      _logger,
      _byteStore,
      _resourceProvider,
      name,
      sourceFactory,
      analysisContext?.contextRoot.workspace,
      declaredVariables,
      _saltForUnlinked,
      _saltForElements,
      featureSetProvider,
      fileContentStrategy: _fileContentStrategy,
      unlinkedUnitStore: _unlinkedUnitStore,
      prefetchFiles: null,
      isGenerated: (_) => false,
      onNewFile: _onNewFile,
      testData: testView?.fileSystem,
    );
    _fileTracker = FileTracker(_logger, _fsState, _fileContentStrategy);
  }

  ResolvedUnitResultImpl _createResolvedUnitImpl({
    required FileState file,
    required UnitAnalysisResult unitResult,
  }) {
    return ResolvedUnitResultImpl(
      session: currentSession,
      path: file.path,
      uri: file.uri,
      exists: file.exists,
      content: file.content,
      lineInfo: file.lineInfo,
      isAugmentation: file.kind is AugmentationFileKind,
      isLibrary: file.kind is LibraryFileKind,
      isPart: file.kind is PartFileKind,
      unit: unitResult.unit,
      errors: unitResult.errors,
    );
  }

  /// If this has not been done yet, schedule discovery of all files that are
  /// potentially available, so that they are included in [knownFiles].
  void _discoverAvailableFiles() {
    _discoverAvailableFilesTask ??= _DiscoverAvailableFilesTask(this);
  }

  /// When we look at a part that has a `part of name;` directive, we
  /// usually don't know the library (in contrast to `part of uri;`).
  /// So, we have no choice than to resolve this part as its own library.
  ///
  /// But parts of `dart:xyz` libraries are special. The reason is that
  /// `dart:core` is always implicitly imported. So, when we start building
  /// the library cycle of such "part as a library", we discover `dart:core`,
  /// and see that it contains our part. So, we don't add it as a library on
  /// its own. But have already committed that it is a library. This causes
  /// an exception in `LinkedElementFactory`.
  ///
  /// The current workaround for this is to discover `dart:core` before any
  /// analysis.
  void _discoverDartCore() {
    if (_hasDartCoreDiscovered) {
      return;
    }
    _hasDartCoreDiscovered = true;

    final dartCoreUri = uriCache.parse('dart:core');
    final dartCoreResolution = _fsState.getFileForUri(dartCoreUri);
    if (dartCoreResolution is UriResolutionFile) {
      final kind = dartCoreResolution.file.kind;
      if (kind is LibraryFileKind) {
        kind.discoverReferencedFiles();
      }
    }
  }

  void _discoverLibraries() {
    if (_hasLibrariesDiscovered) {
      return;
    }
    _hasLibrariesDiscovered = true;

    for (final path in _fileTracker.addedFiles) {
      _fsState.getFileForPath(path);
    }
  }

  void _fillSalt() {
    _fillSaltForUnlinked();
    _fillSaltForElements();
    _fillSaltForResolution();
  }

  void _fillSaltForElements() {
    var buffer = ApiSignature();
    buffer.addInt(DATA_VERSION);
    buffer.addUint32List(_analysisOptions.signatureForElements);
    _addDeclaredVariablesToSignature(buffer);
    _saltForElements = buffer.toUint32List();
  }

  void _fillSaltForResolution() {
    var buffer = ApiSignature();
    buffer.addInt(DATA_VERSION);
    buffer.addBool(enableIndex);
    buffer.addBool(enableDebugResolutionMarkers);
    buffer.addUint32List(_analysisOptions.signature);
    _addDeclaredVariablesToSignature(buffer);

    var workspace = analysisContext?.contextRoot.workspace;
    workspace?.contributeToResolutionSalt(buffer);

    _saltForResolution = buffer.toUint32List();
  }

  void _fillSaltForUnlinked() {
    var buffer = ApiSignature();
    buffer.addInt(DATA_VERSION);
    buffer.addBool(enableIndex);
    buffer.addUint32List(_analysisOptions.unlinkedSignature);
    _saltForUnlinked = buffer.toUint32List();
  }

  /// Load the [AnalysisResult] for the given [file] from the [bytes]. Set
  /// optional [content] and [resolvedUnit].
  AnalysisResult _getAnalysisResultFromBytes(
    FileState file,
    String signature,
    Uint8List bytes, {
    String? content,
    CompilationUnit? resolvedUnit,
    List<AnalysisError>? errors,
  }) {
    var unit = AnalysisDriverResolvedUnit.fromBuffer(bytes);
    errors ??= _getErrorsFromSerialized(file, unit.errors);
    _updateHasErrorOrWarningFlag(file, errors);
    var index = unit.index!;
    if (content != null && resolvedUnit != null) {
      var resolvedUnitResult = ResolvedUnitResultImpl(
        session: currentSession,
        path: file.path,
        uri: file.uri,
        exists: file.exists,
        content: content,
        lineInfo: file.lineInfo,
        isAugmentation: file.kind is AugmentationFileKind,
        isLibrary: file.kind is LibraryFileKind,
        isPart: file.kind is PartFileKind,
        unit: resolvedUnit,
        errors: errors,
      );
      return AnalysisResult.unit(signature, resolvedUnitResult, index);
    } else {
      var errorsResult = _createErrorsResultImpl(
        file: file,
        errors: errors,
      );
      return AnalysisResult.errors(signature, errorsResult, index);
    }
  }

  /// Return [AnalysisError]s for the given [serialized] errors.
  List<AnalysisError> _getErrorsFromSerialized(
      FileState file, List<AnalysisDriverUnitError> serialized) {
    List<AnalysisError> errors = <AnalysisError>[];
    for (AnalysisDriverUnitError error in serialized) {
      var analysisError = ErrorEncoding.decode(file.source, error);
      if (analysisError != null) {
        errors.add(analysisError);
      }
    }
    return errors;
  }

  /// Return the key to store fully resolved results for the [signature].
  String _getResolvedUnitKey(String signature) {
    return '$signature.resolved';
  }

  /// Return the signature that identifies fully resolved results for the [file]
  /// in the [library], e.g. element model, errors, index, etc.
  String _getResolvedUnitSignature(LibraryFileKind library, FileState file) {
    ApiSignature signature = ApiSignature();
    signature.addUint32List(_saltForResolution);
    signature.addString(library.file.uriStr);
    signature.addString(library.libraryCycle.apiSignature);
    signature.addString(file.uriStr);
    signature.addString(file.contentHash);
    return signature.toHex();
  }

  bool _hasLibraryByUri(String uriStr) {
    var uri = uriCache.parse(uriStr);
    var fileOr = _fsState.getFileForUri(uri);
    return switch (fileOr) {
      null => false,
      UriResolutionFile(:final file) => file.exists,
      UriResolutionExternalLibrary() => true,
    };
  }

  bool _isAbsolutePath(String path) {
    return _resourceProvider.pathContext.isAbsolute(path);
  }

  bool _isLibraryWithPriorityFile(LibraryFileKind library) {
    for (final file in library.files) {
      if (_priorityFiles.contains(file.path)) {
        return true;
      }
    }
    return false;
  }

  Future<void> _maybeDispose() async {
    if (_disposeRequests.isNotEmpty) {
      _scheduler.remove(this);
      clearLibraryContext();

      for (final completer in _disposeRequests.toList()) {
        completer.complete();
      }
    }
  }

  /// We detected that one of the required `dart` libraries is missing.
  /// Return the empty analysis result with the error.
  AnalysisResult _newMissingDartLibraryResult(
      FileState file, String missingUri) {
    // TODO(scheglov) Find a better way to report this.
    var errorsResult = ErrorsResultImpl(
      session: currentSession,
      path: file.path,
      uri: file.uri,
      lineInfo: file.lineInfo,
      isAugmentation: file.kind is AugmentationFileKind,
      isLibrary: file.kind is LibraryFileKind,
      isPart: file.kind is PartFileKind,
      errors: [
        AnalysisError.tmp(
          source: file.source,
          offset: 0,
          length: 0,
          errorCode: CompileTimeErrorCode.MISSING_DART_LIBRARY,
          arguments: [missingUri],
        ),
      ],
    );
    return AnalysisResult.errors(
        'missing', errorsResult, AnalysisDriverUnitIndexBuilder());
  }

  void _onNewFile(FileState file) {
    final ownedFiles = this.ownedFiles;
    if (ownedFiles != null) {
      if (addedFiles.contains(file.path)) {
        ownedFiles.addAdded(file.uri, this);
      } else {
        ownedFiles.addKnown(file.uri, this);
      }
    }
  }

  void _removePotentiallyAffectedLibraries(
    Set<String> accumulatedAffected,
    String path,
  ) {
    var affected = <FileState>{};
    _fsState.collectAffected(path, affected);

    final removedKeys = <String>{};
    _libraryContext?.remove(affected, removedKeys);

    // TODO(scheglov) Eventually list of `LibraryOrAugmentationFileKind`.
    for (final file in affected) {
      final kind = file.kind;
      if (kind is LibraryFileKind) {
        kind.invalidateLibraryCycle();
      }
      accumulatedAffected.add(file.path);
    }

    _libraryContext?.elementFactory.replaceAnalysisSession(
      AnalysisSessionImpl(this),
    );
  }

  void _reportException(String path, Object exception, StackTrace stackTrace) {
    String? contextKey;
    if (exception is _ExceptionState) {
      var state = exception;
      exception = exception.exception;
      stackTrace = state.stackTrace;
      contextKey = state.contextKey;
    }

    CaughtException caught = CaughtException(exception, stackTrace);

    var fileContentMap = <String, String>{};

    try {
      final file = _fsState.getFileForPath(path);
      final fileKind = file.kind;
      final libraryKind = fileKind.library;
      if (libraryKind != null) {
        for (final file in libraryKind.files) {
          fileContentMap[file.path] = file.content;
        }
      } else {
        final file = fileKind.file;
        fileContentMap[file.path] = file.content;
      }
    } catch (_) {
      // We might get an exception while parsing to access parts.
      // Ignore, continue with the exception that we are reporting now.
    }

    if (exception is CaughtExceptionWithFiles) {
      for (var nested in exception.fileContentMap.entries) {
        fileContentMap['nested-${nested.key}'] = nested.value;
      }
    }

    _exceptionController.add(
      ExceptionResult(
        filePath: path,
        fileContentMap: fileContentMap,
        exception: caught,
        contextKey: contextKey,
      ),
    );
  }

  Future<ResolvedForCompletionResultImpl?> _resolveForCompletion(
    _ResolveForCompletionRequest request,
  ) async {
    return request.performance.runAsync('body', (performance) async {
      final path = request.path;
      if (!_isAbsolutePath(path)) {
        return null;
      }

      if (!_fsState.hasUri(path)) {
        return null;
      }

      var file = _fsState.getFileForPath(path);

      // Prepare the library - the file itself, or the known library.
      final kind = file.kind;
      final library = kind.library ?? kind.asLibrary;

      await performance.runAsync(
        'libraryContext',
        (performance) async {
          await libraryContext.load(
            targetLibrary: library,
            performance: performance,
          );
        },
      );
      var unitElement = libraryContext.computeUnitElement(library, file);

      var analysisResult = LibraryAnalyzer(
        analysisOptions as AnalysisOptionsImpl,
        declaredVariables,
        libraryContext.elementFactory.libraryOfUri2(library.file.uri),
        libraryContext.elementFactory.analysisSession.inheritanceManager,
        library,
        resourceProvider.pathContext,
        testingData: testingData,
      ).analyzeForCompletion(
        file: file,
        offset: request.offset,
        unitElement: unitElement,
        performance: performance,
      );

      return ResolvedForCompletionResultImpl(
        analysisSession: currentSession,
        path: path,
        uri: file.uri,
        exists: file.exists,
        content: file.content,
        lineInfo: file.lineInfo,
        parsedUnit: analysisResult.parsedUnit,
        unitElement: unitElement,
        resolvedNodes: analysisResult.resolvedNodes,
      );
    });
  }

  String? _storeExceptionContext(String path, LibraryFileKind library,
      Object exception, StackTrace stackTrace) {
    if (allowedNumberOfContextsToWrite <= 0) {
      return null;
    } else {
      allowedNumberOfContextsToWrite--;
    }
    try {
      final contextFiles = library.files
          .map((file) => AnalysisDriverExceptionFileBuilder(
              path: file.path, content: file.content))
          .toList();
      contextFiles.sort((a, b) => a.path.compareTo(b.path));
      AnalysisDriverExceptionContextBuilder contextBuilder =
          AnalysisDriverExceptionContextBuilder(
              path: path,
              exception: exception.toString(),
              stackTrace: stackTrace.toString(),
              files: contextFiles);
      var bytes = contextBuilder.toBuffer();

      String twoDigits(int n) {
        if (n >= 10) return '$n';
        return '0$n';
      }

      String threeDigits(int n) {
        if (n >= 100) return '$n';
        if (n >= 10) return '0$n';
        return '00$n';
      }

      DateTime time = DateTime.now();
      String m = twoDigits(time.month);
      String d = twoDigits(time.day);
      String h = twoDigits(time.hour);
      String min = twoDigits(time.minute);
      String sec = twoDigits(time.second);
      String ms = threeDigits(time.millisecond);
      String key = 'exception_${time.year}$m${d}_$h$min${sec}_$ms';

      _byteStore.putGet(key, bytes);
      return key;
    } catch (_) {
      return null;
    }
  }

  /// The driver supports only absolute paths, this method is used to validate
  /// any input paths to prevent errors later.
  void _throwIfNotAbsolutePath(String path) {
    if (!_isAbsolutePath(path)) {
      throw ArgumentError('Only absolute paths are supported: $path');
    }
  }

  /// Given the list of [errors] for the [file], update the [file]'s
  /// [FileState.hasErrorOrWarning] flag.
  void _updateHasErrorOrWarningFlag(
      FileState file, List<AnalysisError> errors) {
    for (AnalysisError error in errors) {
      ErrorSeverity severity = error.errorCode.errorSeverity;
      if (severity == ErrorSeverity.ERROR) {
        file.hasErrorOrWarning = true;
        return;
      }
    }
    file.hasErrorOrWarning = false;
  }
}

/// A generic schedulable interface via the AnalysisDriverScheduler. Currently
/// only implemented by [AnalysisDriver] and the angular plugin, at least as
/// a temporary measure until the official plugin API is ready (and a different
/// scheduler is used)
abstract class AnalysisDriverGeneric {
  /// Return `true` if the driver has a file to analyze.
  bool get hasFilesToAnalyze;

  /// Set the list of files that the driver should try to analyze sooner.
  ///
  /// Every path in the list must be absolute and normalized.
  ///
  /// The driver will produce the results through the [results] stream. The
  /// exact order in which results are produced is not defined, neither
  /// between priority files, nor between priority and non-priority files.
  set priorityFiles(List<String> priorityPaths);

  /// Return the priority of work that the driver needs to perform.
  AnalysisDriverPriority get workPriority;

  /// Add the file with the given [path] to the set of files that are explicitly
  /// being analyzed.
  ///
  /// The [path] must be absolute and normalized.
  ///
  /// The results of analysis are eventually produced by the [results] stream.
  void addFile(String path);

  /// Notify the driver that the client is going to stop using it.
  Future<void> dispose2();

  /// Perform a single chunk of work and produce [results].
  Future<void> performWork();
}

/// Priorities of [AnalysisDriver] work. The farther a priority to the beginning
/// of the list, the earlier the corresponding [AnalysisDriver] should be asked
/// to perform work.
enum AnalysisDriverPriority {
  nothing,
  general,
  generalWithErrors,
  generalImportChanged,
  generalChanged,
  changedFiles,
  priority,
  interactive,
  completion
}

/// Instances of this class schedule work in multiple [AnalysisDriver]s so that
/// work with the highest priority is performed first.
class AnalysisDriverScheduler {
  /// Time interval in milliseconds before pumping the event queue.
  ///
  /// Relinquishing execution flow and running the event loop after every task
  /// has too much overhead. Instead we use a fixed length of time, so we can
  /// spend less time overall and still respond quickly enough.
  static const int _MS_BEFORE_PUMPING_EVENT_QUEUE = 2;

  /// Event queue pumping is required to allow IO and other asynchronous data
  /// processing while analysis is active. For example Analysis Server needs to
  /// be able to process `updateContent` or `setPriorityFiles` requests while
  /// background analysis is in progress.
  ///
  /// The number of pumpings is arbitrary, might be changed if we see that
  /// analysis or other data processing tasks are starving. Ideally we would
  /// need to run all asynchronous operations using a single global scheduler.
  static const int _NUMBER_OF_EVENT_QUEUE_PUMPINGS = 128;

  final PerformanceLog _logger;

  /// The object used to watch as analysis drivers are created and deleted.
  final DriverWatcher? driverWatcher;

  final List<AnalysisDriverGeneric> _drivers = [];
  final Monitor _hasWork = Monitor();
  final StatusSupport _statusSupport = StatusSupport();

  bool _started = false;

  /// The optional worker that is invoked when its work priority is higher
  /// than work priorities in drivers.
  ///
  /// Don't use outside of Analyzer and Analysis Server.
  SchedulerWorker? outOfBandWorker;

  AnalysisDriverScheduler(this._logger, {this.driverWatcher});

  /// Return `true` if we are currently analyzing code.
  bool get isAnalyzing => _hasFilesToAnalyze;

  /// Return the stream that produces [AnalysisStatus] events.
  Stream<AnalysisStatus> get status => _statusSupport.stream;

  /// Return `true` if there is a driver with a file to analyze.
  bool get _hasFilesToAnalyze {
    for (AnalysisDriverGeneric driver in _drivers) {
      if (driver.hasFilesToAnalyze) {
        return true;
      }
    }
    return false;
  }

  /// Add the given [driver] and schedule it to perform its work.
  void add(AnalysisDriverGeneric driver) {
    _drivers.add(driver);
    _hasWork.notify();
    if (driver is AnalysisDriver && driver.analysisContext != null) {
      driverWatcher?.addedDriver(driver);
    }
  }

  /// Notify that there is a change to the [driver], it might need to
  /// perform some work.
  void notify(AnalysisDriverGeneric? driver) {
    // TODO(brianwilkerson) Consider removing the parameter, given that it isn't
    //  referenced in the body.
    _hasWork.notify();
    _statusSupport.preTransitionToAnalyzing();
  }

  /// Remove the given [driver] from the scheduler, so that it will not be
  /// asked to perform any new work.
  void remove(AnalysisDriverGeneric driver) {
    if (driver is AnalysisDriver) {
      driverWatcher?.removedDriver(driver);
    }
    _drivers.remove(driver);
    _hasWork.notify();
  }

  /// Start the scheduler, so that any [AnalysisDriver] created before or
  /// after will be asked to perform work.
  void start() {
    if (_started) {
      throw StateError('The scheduler has already been started.');
    }
    _started = true;
    _run();
  }

  /// Usually we transition status to analyzing only if there are files to
  /// analyze. However when used in the server, there are rare cases when
  /// analysis roots don't have any Dart files, but for consistency we still
  /// want to get status to transition to analysis, and back to idle.
  void transitionToAnalyzingToIdleIfNoFilesToAnalyze() {
    if (!_hasFilesToAnalyze) {
      _statusSupport.transitionToAnalyzing();
      _statusSupport.transitionToIdle();
    }
  }

  /// Return a future that will be completed the next time the status is idle.
  ///
  /// If the status is currently idle, the returned future will be signaled
  /// immediately.
  Future<void> waitForIdle() => _statusSupport.waitForIdle();

  /// Run infinitely analysis cycle, selecting the drivers with the highest
  /// priority first.
  Future<void> _run() async {
    // Give other microtasks the time to run before doing the analysis cycle.
    await null;
    Stopwatch timer = Stopwatch()..start();
    PerformanceLogSection? analysisSection;
    while (true) {
      // Pump the event queue.
      if (timer.elapsedMilliseconds > _MS_BEFORE_PUMPING_EVENT_QUEUE) {
        await _pumpEventQueue(_NUMBER_OF_EVENT_QUEUE_PUMPINGS);
        timer.reset();
      }

      await _hasWork.signal;

      for (final driver in _drivers.toList()) {
        if (driver is AnalysisDriver) {
          await driver._maybeDispose();
        }
      }

      for (var driver in _drivers) {
        if (driver is AnalysisDriver) {
          driver._applyPendingFileChanges();
        }
      }

      // Transition to analyzing if there are files to analyze.
      if (_hasFilesToAnalyze) {
        _statusSupport.transitionToAnalyzing();
        analysisSection ??= _logger.enter('Analyzing');
      }

      // Find the driver with the highest priority.
      late AnalysisDriverGeneric bestDriver;
      AnalysisDriverPriority bestPriority = AnalysisDriverPriority.nothing;
      for (AnalysisDriverGeneric driver in _drivers) {
        AnalysisDriverPriority priority = driver.workPriority;
        if (priority.index > bestPriority.index) {
          bestDriver = driver;
          bestPriority = priority;
        }
      }

      if (outOfBandWorker != null) {
        var workerPriority = outOfBandWorker!.workPriority;
        if (workerPriority != AnalysisDriverPriority.nothing) {
          if (workerPriority.index > bestPriority.index) {
            await outOfBandWorker!.performWork();
            _hasWork.notify();
            continue;
          }
        }
      }

      // Transition to idle if no files to analyze.
      if (!_hasFilesToAnalyze) {
        _statusSupport.transitionToIdle();
        analysisSection?.exit();
        analysisSection = null;
      }

      // Continue to sleep if no work to do.
      if (bestPriority == AnalysisDriverPriority.nothing) {
        continue;
      }

      // Ask the driver to perform a chunk of work.
      await bestDriver.performWork();

      // Schedule one more cycle.
      _hasWork.notify();
    }
  }

  /// Returns a [Future] that completes after performing [times] pumpings of
  /// the event queue.
  static Future _pumpEventQueue(int times) {
    if (times == 0) {
      return Future.value();
    }
    return Future.delayed(Duration.zero, () => _pumpEventQueue(times - 1));
  }
}

class AnalysisDriverTestView {
  final fileSystem = FileSystemTestData();

  late final libraryContext = LibraryContextTestData(
    fileSystemTestData: fileSystem,
  );

  late final AnalysisDriver driver;

  int numOfAnalyzedLibraries = 0;

  FileTracker get fileTracker => driver._fileTracker;

  Set<String> get loadedLibraryUriSet {
    var elementFactory = driver.libraryContext.elementFactory;
    var libraryReferences = elementFactory.rootReference.children;
    return libraryReferences.map((e) => e.name).toSet();
  }

  Map<String, ResolvedUnitResult> get priorityResults {
    return driver._priorityResults;
  }
}

/// The result of analyzing of a single file.
///
/// These results are self-consistent, i.e. the file content, line info, the
/// resolved unit correspond to each other. All referenced elements, even
/// external ones, are also self-consistent. But none of the results is
/// guaranteed to be consistent with the state of the files.
///
/// Every result is independent, and is not guaranteed to be consistent with
/// any previously returned result, even inside of the same library.
class AnalysisResult {
  /// The signature of the result based on the content of the file, and the
  /// transitive closure of files imported and exported by the library of
  /// the requested file.
  final String _signature;

  final bool isUnchangedErrors;

  /// Is not `null` if this result is a result with errors.
  /// Otherwise is `null`, and usually [unitResult] is set.
  final ErrorsResultImpl? errorsResult;

  /// Is not `null` if this result is a result with a resolved unit.
  /// Otherwise is `null`, and usually [errorsResult] is set.
  final ResolvedUnitResultImpl? unitResult;

  /// The index of the unit.
  final AnalysisDriverUnitIndex? _index;

  AnalysisResult.errors(
      this._signature, this.errorsResult, AnalysisDriverUnitIndex index)
      : isUnchangedErrors = false,
        unitResult = null,
        _index = index;

  AnalysisResult.unchangedErrors(this._signature)
      : isUnchangedErrors = true,
        errorsResult = null,
        unitResult = null,
        _index = null;

  AnalysisResult.unit(
      this._signature, this.unitResult, AnalysisDriverUnitIndex index)
      : isUnchangedErrors = false,
        errorsResult = null,
        _index = index;
}

/// An object that watches for the creation and removal of analysis drivers.
///
/// Clients may not extend, implement or mix-in this class.
abstract class DriverWatcher {
  /// The context manager has just added the given analysis [driver]. This method
  /// must be called before the driver has been allowed to perform any analysis.
  void addedDriver(AnalysisDriver driver);

  /// The context manager has just removed the given analysis [driver].
  void removedDriver(AnalysisDriver driver);
}

class ErrorEncoding {
  static AnalysisError? decode(
    Source source,
    AnalysisDriverUnitError error,
  ) {
    String errorName = error.uniqueName;
    ErrorCode? errorCode =
        errorCodeByUniqueName(errorName) ?? _lintCodeByUniqueName(errorName);
    if (errorCode == null) {
      // This could fail because the error code is no longer defined, or, in
      // the case of a lint rule, if the lint rule has been disabled since the
      // errors were written.
      AnalysisEngine.instance.instrumentationService
          .logError('No error code for "$error" in "$source"');
      return null;
    }

    var contextMessages = <DiagnosticMessageImpl>[];
    for (var message in error.contextMessages) {
      var url = message.url;
      contextMessages.add(
        DiagnosticMessageImpl(
          filePath: message.filePath,
          length: message.length,
          message: message.message,
          offset: message.offset,
          url: url.isEmpty ? null : url,
        ),
      );
    }

    return AnalysisError.forValues(
      source: source,
      offset: error.offset,
      length: error.length,
      errorCode: errorCode,
      message: error.message,
      correctionMessage: error.correction.isEmpty ? null : error.correction,
      contextMessages: contextMessages,
    );
  }

  static AnalysisDriverUnitErrorBuilder encode(AnalysisError error) {
    var contextMessages = <DiagnosticMessageBuilder>[];
    for (var message in error.contextMessages) {
      contextMessages.add(
        DiagnosticMessageBuilder(
          filePath: message.filePath,
          length: message.length,
          message: message.messageText(includeUrl: false),
          offset: message.offset,
          url: message.url,
        ),
      );
    }

    return AnalysisDriverUnitErrorBuilder(
      offset: error.offset,
      length: error.length,
      uniqueName: error.errorCode.uniqueName,
      message: error.message,
      correction: error.correction ?? '',
      contextMessages: contextMessages,
    );
  }

  /// Return the lint code with the given [errorName], or `null` if there is no
  /// lint registered with that name.
  static ErrorCode? _lintCodeByUniqueName(String errorName) {
    return linter.Registry.ruleRegistry.codeForUniqueName(errorName);
  }
}

/// Exception that happened during analysis.
class ExceptionResult {
  /// The path of the library being analyzed when the [exception] happened.
  ///
  /// Absolute and normalized.
  final String filePath;

  /// The content of the library and its parts.
  final Map<String, String> fileContentMap;

  /// The exception during analysis of the file with the [filePath].
  final CaughtException exception;

  /// If the exception happened during a file analysis, and the context in which
  /// the exception happened was stored, this field is the key of the context
  /// in the byte store. May be `null` if the context is unknown, the maximum
  /// number of context to store was reached, etc.
  final String? contextKey;

  ExceptionResult({
    required this.filePath,
    required this.fileContentMap,
    required this.exception,
    required this.contextKey,
  });
}

/// Container that keeps track of file owners.
class OwnedFiles {
  /// Key: the absolute file URI.
  /// Value: the driver to which the file is added.
  final Map<Uri, AnalysisDriver> addedFiles = {};

  /// Key: the absolute file URI.
  /// Value: a driver in which this file is available via dependencies.
  /// This map does not contain any files that are in [addedFiles].
  final Map<Uri, AnalysisDriver> knownFiles = {};

  void addAdded(Uri uri, AnalysisDriver analysisDriver) {
    addedFiles[uri] ??= analysisDriver;
    knownFiles.remove(uri);
  }

  void addKnown(Uri uri, AnalysisDriver analysisDriver) {
    if (!addedFiles.containsKey(uri)) {
      knownFiles[uri] = analysisDriver;
    }
  }
}

/// Worker in [AnalysisDriverScheduler].
abstract class SchedulerWorker {
  /// Return the priority of work that this worker needs to perform.
  AnalysisDriverPriority get workPriority;

  /// Perform a single chunk of work.
  Future<void> performWork();
}

/// Task that discovers all files that are available to the driver, and makes
/// them known.
class _DiscoverAvailableFilesTask {
  static const int _MS_WORK_INTERVAL = 5;

  final AnalysisDriver driver;

  final Completer<void> completer = Completer<void>();

  Iterator<Folder>? folderIterator;

  final List<String> files = [];

  int fileIndex = 0;

  _DiscoverAvailableFilesTask(this.driver);

  bool get isCompleted => completer.isCompleted;

  /// Perform the next piece of work, and set [isCompleted] to `true` to
  /// indicate that the task is done, or keeps it `false` to indicate that the
  /// task should continue to be run.
  void perform() {
    if (folderIterator == null) {
      files.addAll(driver.addedFiles);

      // Discover SDK libraries.
      var dartSdk = driver._sourceFactory.dartSdk;
      if (dartSdk != null) {
        for (var sdkLibrary in dartSdk.sdkLibraries) {
          var file = dartSdk.mapDartUri(sdkLibrary.shortName)!.fullName;
          files.add(file);
        }
      }

      // Discover files in package/lib folders.
      var packageMap = driver._sourceFactory.packageMap;
      if (packageMap != null) {
        folderIterator = packageMap.values.expand((f) => f).iterator;
      } else {
        folderIterator = <Folder>[].iterator;
      }
    }

    // List each package/lib folder recursively.
    Stopwatch timer = Stopwatch()..start();
    while (folderIterator!.moveNext()) {
      var folder = folderIterator!.current;
      _appendFilesRecursively(folder);

      // Note: must check if we are exiting before calling moveNext()
      // otherwise we will skip one iteration of the loop when we come back.
      if (timer.elapsedMilliseconds > _MS_WORK_INTERVAL) {
        return;
      }
    }

    // Get know files one by one.
    while (fileIndex < files.length) {
      if (timer.elapsedMilliseconds > _MS_WORK_INTERVAL) {
        return;
      }
      var file = files[fileIndex++];
      driver._fsState.getFileForPath(file);
    }

    // The task is done, clean up.
    folderIterator = null;
    files.clear();
    completer.complete();
  }

  void _appendFilesRecursively(Folder folder) {
    try {
      var pathContext = driver.resourceProvider.pathContext;
      for (var child in folder.getChildren()) {
        if (child is File) {
          var path = child.path;
          if (file_paths.isDart(pathContext, path)) {
            files.add(path);
          }
        } else if (child is Folder) {
          _appendFilesRecursively(child);
        }
      }
    } catch (_) {}
  }
}

/// Information about an exception and its context.
class _ExceptionState {
  final Object exception;
  final StackTrace stackTrace;

  /// The key under which the context of the exception was stored, or `null`
  /// if unknown, the maximum number of context to store was reached, etc.
  final String? contextKey;

  _ExceptionState(this.exception, this.stackTrace, this.contextKey);

  @override
  String toString() => '$exception\n$stackTrace';
}

class _FileChange {
  final String path;
  final _FileChangeKind kind;

  _FileChange(this.path, this.kind);

  @override
  String toString() {
    return '[path: $path][kind: $kind]';
  }
}

enum _FileChangeKind { add, change, remove }

/// Task that computes the list of files that were added to the driver and
/// declare a class member with the given [name].
class _FilesDefiningClassMemberNameTask {
  static const int _MS_WORK_INTERVAL = 5;

  final AnalysisDriver driver;
  final String name;
  final Completer<List<String>> completer = Completer<List<String>>();

  final List<String> definingFiles = <String>[];
  final Set<String> checkedFiles = <String>{};
  final List<String> filesToCheck = <String>[];

  _FilesDefiningClassMemberNameTask(this.driver, this.name);

  /// Perform work for a fixed length of time, and complete the [completer] to
  /// either return `true` to indicate that the task is done, or return `false`
  /// to indicate that the task should continue to be run.
  ///
  /// Each invocation of an asynchronous method has overhead, which looks as
  /// `_SyncCompleter.complete` invocation, we see as much as 62% in some
  /// scenarios. Instead we use a fixed length of time, so we can spend less time
  /// overall and keep quick enough response time.
  bool perform() {
    Stopwatch timer = Stopwatch()..start();
    while (timer.elapsedMilliseconds < _MS_WORK_INTERVAL) {
      // Prepare files to check.
      if (filesToCheck.isEmpty) {
        Set<String> newFiles = driver.knownFiles.difference(checkedFiles);
        filesToCheck.addAll(newFiles);
      }

      // If no more files to check, complete and done.
      if (filesToCheck.isEmpty) {
        completer.complete(definingFiles);
        return true;
      }

      // Check the next file.
      String path = filesToCheck.removeLast();
      FileState file = driver._fsState.getFileForPath(path);
      if (file.definedClassMemberNames.contains(name)) {
        definingFiles.add(path);
      }
      checkedFiles.add(path);
    }

    // We're not done yet.
    return false;
  }
}

/// Task that computes the list of files that were added to the driver and
/// have at least one reference to an identifier [name] defined outside of the
/// file.
class _FilesReferencingNameTask {
  static const int _WORK_FILES = 100;
  static const int _MS_WORK_INTERVAL = 5;

  final AnalysisDriver driver;
  final String name;
  final Completer<List<String>> completer = Completer<List<String>>();

  int fileStamp = -1;
  List<FileState>? filesToCheck;
  int filesToCheckIndex = -1;

  final List<String> referencingFiles = <String>[];

  _FilesReferencingNameTask(this.driver, this.name);

  /// Perform work for a fixed length of time, and complete the [completer] to
  /// either return `true` to indicate that the task is done, or return `false`
  /// to indicate that the task should continue to be run.
  ///
  /// Each invocation of an asynchronous method has overhead, which looks as
  /// `_SyncCompleter.complete` invocation, we see as much as 62% in some
  /// scenarios. Instead we use a fixed length of time, so we can spend less time
  /// overall and keep quick enough response time.
  bool perform() {
    if (driver._fsState.fileStamp != fileStamp) {
      filesToCheck = null;
      referencingFiles.clear();
    }

    // Prepare files to check.
    if (filesToCheck == null) {
      fileStamp = driver._fsState.fileStamp;
      filesToCheck = driver._fsState.knownFiles.toList();
      filesToCheckIndex = 0;
    }

    Stopwatch timer = Stopwatch()..start();
    while (filesToCheckIndex < filesToCheck!.length) {
      if (filesToCheckIndex % _WORK_FILES == 0 &&
          timer.elapsedMilliseconds > _MS_WORK_INTERVAL) {
        return false;
      }
      FileState file = filesToCheck![filesToCheckIndex++];
      if (file.referencedNames.contains(name)) {
        referencingFiles.add(file.path);
      }
    }

    // If no more files to check, complete and done.
    completer.complete(referencingFiles);
    return true;
  }
}

class _ResolveForCompletionRequest {
  final String path;
  final int offset;
  final OperationPerformanceImpl performance;
  final Completer<ResolvedForCompletionResultImpl?> completer = Completer();

  _ResolveForCompletionRequest({
    required this.path,
    required this.offset,
    required this.performance,
  });
}