pkg/analyzer_cli/lib/src/options.dart - sdk.git - Git at Google

 // Copyright (c) 2015, 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:io' as io;

 import 'package:analyzer/dart/analysis/features.dart';
 import 'package:analyzer/file_system/file_system.dart';
 import 'package:analyzer/src/dart/analysis/experiments.dart';
 import 'package:analyzer/src/generated/engine.dart' show AnalysisOptionsImpl;
 import 'package:analyzer/src/util/file_paths.dart' as file_paths;
 import 'package:analyzer/src/util/sdk.dart';
 import 'package:analyzer_cli/src/ansi.dart' as ansi;
 import 'package:analyzer_cli/src/driver.dart';
 import 'package:args/args.dart';
 import 'package:pub_semver/pub_semver.dart';

 const _analysisOptionsFileOption = 'options';
 const _binaryName = 'dartanalyzer';
 const _defaultLanguageVersionOption = 'default-language-version';
 const _defineVariableOption = 'D';
 const _enableExperimentOption = 'enable-experiment';
 const _enableInitializingFormalAccessFlag = 'initializing-formal-access';
 const _ignoreUnrecognizedFlagsFlag = 'ignore-unrecognized-flags';
 const _packagesOption = 'packages';
 const _sdkPathOption = 'dart-sdk';

 /// Shared exit handler.
 ///
 /// *Visible for testing.*
 ExitHandler exitHandler = io.exit;

 T cast<T>(dynamic value) => value as T;

 T? castNullable<T>(dynamic value) => value as T?;

 /// Print the given [message] to stderr and exit with the given [exitCode].
 void printAndFail(String message, {int exitCode = 15}) {
   errorSink.writeln(message);
   exitHandler(exitCode);
 }

 /// Exit handler.
 ///
 /// *Visible for testing.*
 typedef ExitHandler = void Function(int code);

 /// Analyzer commandline configuration options.
 class CommandLineOptions {
   final ArgResults _argResults;

   /// The file path of the analysis options file that should be used in place of
   /// any file in the root directory or a parent of the root directory,
   /// or `null` if the normal lookup mechanism should be used.
   String? defaultAnalysisOptionsPath;

   /// The file path of the .packages file that should be used in place of any
   /// file found using the normal (Package Specification DEP) lookup mechanism,
   /// or `null` if the normal lookup mechanism should be used.
   String? defaultPackagesPath;

   /// A table mapping variable names to values for the declared variables.
   final Map<String, String> declaredVariables = {};

   /// The path to the dart SDK.
   String? dartSdkPath;

   /// Whether to disable cache flushing. This option can improve analysis
   /// speed at the expense of memory usage. It may also be useful for working
   /// around bugs.
   final bool disableCacheFlushing;

   /// Whether to display version information
   final bool displayVersion;

   /// Whether to ignore unrecognized flags
   final bool ignoreUnrecognizedFlags;

   /// Whether to log additional analysis messages and exceptions
   final bool log;

   /// Whether to use 'json' format for error display
   final bool jsonFormat;

   /// Whether to use 'machine' format for error display
   final bool machineFormat;

   /// The path to a file to write a performance log.
   /// (Or null if not enabled.)
   final String? perfReport;

   /// Batch mode (for unit testing)
   final bool batchMode;

   /// The source files to analyze
   final List<String> sourceFiles;

   /// Emit output in a verbose mode.
   final bool verbose;

   /// Use ANSI color codes for output.
   final bool color;

   /// Whether we should analyze the given source for the purposes of training a
   /// Dart analyzer snapshot.
   final bool trainSnapshot;

   /// Initialize options from the given parsed [args].
   CommandLineOptions._fromArgs(
     ResourceProvider resourceProvider,
     ArgResults args,
   )   : _argResults = args,
         dartSdkPath = castNullable(args[_sdkPathOption]),
         disableCacheFlushing = cast(args['disable-cache-flushing']),
         displayVersion = cast(args['version']),
         ignoreUnrecognizedFlags = cast(args[_ignoreUnrecognizedFlagsFlag]),
         log = cast(args['log']),
         jsonFormat = args['format'] == 'json',
         machineFormat = args['format'] == 'machine',
         perfReport = castNullable(args['x-perf-report']),
         batchMode = cast(args['batch']),
         sourceFiles = args.rest,
         trainSnapshot = cast(args['train-snapshot']),
         verbose = cast(args['verbose']),
         color = cast(args['color']) {
     //
     // File locations.
     //
     defaultAnalysisOptionsPath = _absoluteNormalizedPath(
       resourceProvider,
       castNullable(args[_analysisOptionsFileOption]),
     );
     defaultPackagesPath = _absoluteNormalizedPath(
       resourceProvider,
       castNullable(args[_packagesOption]),
     );

     //
     // Declared variables.
     //
     var variables = (args[_defineVariableOption] as List).cast<String>();
     for (var variable in variables) {
       var index = variable.indexOf('=');
       if (index < 0) {
         // TODO(brianwilkerson): Decide the semantics we want in this case.
         // The VM prints "No value given to -D option", then tries to load '-Dfoo'
         // as a file and dies. Unless there was nothing after the '-D', in which
         // case it prints the warning and ignores the option.
       } else {
         var name = variable.substring(0, index);
         if (name.isNotEmpty) {
           // TODO(brianwilkerson): Decide the semantics we want in the case where
           // there is no name. If there is no name, the VM tries to load a file
           // named '-D' and dies.
           declaredVariables[name] = variable.substring(index + 1);
         }
       }
     }
   }

   /// The default language version for files that are not in a package.
   /// (Or null if no default language version to force.)
   String? get defaultLanguageVersion {
     return castNullable(_argResults[_defaultLanguageVersionOption]);
   }

   /// A list of the names of the experiments that are to be enabled.
   List<String>? get enabledExperiments {
     return castNullable(_argResults[_enableExperimentOption]);
   }

   /// Update the [analysisOptions] with flags that the user specified
   /// explicitly. The [analysisOptions] are usually loaded from one of
   /// `analysis_options.yaml` files, possibly with includes. We consider
   /// flags that the user specified as command line options more important,
   /// so override the corresponding options.
   void updateAnalysisOptions(AnalysisOptionsImpl analysisOptions) {
     var defaultLanguageVersion = this.defaultLanguageVersion;
     if (defaultLanguageVersion != null) {
       var nonPackageLanguageVersion =
           Version.parse('$defaultLanguageVersion.0');
       analysisOptions.nonPackageLanguageVersion = nonPackageLanguageVersion;
       analysisOptions.nonPackageFeatureSet = FeatureSet.latestLanguageVersion()
           .restrictToVersion(nonPackageLanguageVersion);
     }

     var enabledExperiments = this.enabledExperiments!;
     if (enabledExperiments.isNotEmpty) {
       analysisOptions.contextFeatures = FeatureSet.fromEnableFlags2(
         sdkLanguageVersion: ExperimentStatus.currentVersion,
         flags: enabledExperiments,
       );
     }
   }

   /// Return a list of command-line arguments containing all of the given [args]
   /// that are defined by the given [parser]. An argument is considered to be
   /// defined by the parser if
   /// - it starts with '--' and the rest of the argument (minus any value
   ///   introduced by '=') is the name of a known option,
   /// - it starts with '-' and the rest of the argument (minus any value
   ///   introduced by '=') is the name of a known abbreviation, or
   /// - it starts with something other than '--' or '-'.
   ///
   /// This function allows command-line tools to implement the
   /// '--ignore-unrecognized-flags' option.
   static List<String> filterUnknownArguments(
       List<String> args, ArgParser parser) {
     var knownOptions = <String>{};
     var knownAbbreviations = <String>{};
     parser.options.forEach((String name, Option option) {
       knownOptions.add(name);
       var abbreviation = option.abbr;
       if (abbreviation != null) {
         knownAbbreviations.add(abbreviation);
       }
       if (option.negatable ?? false) {
         knownOptions.add('no-$name');
       }
     });
     String optionName(int prefixLength, String argument) {
       var equalsOffset = argument.lastIndexOf('=');
       if (equalsOffset < 0) {
         return argument.substring(prefixLength);
       }
       return argument.substring(prefixLength, equalsOffset);
     }

     var filtered = <String>[];
     for (var i = 0; i < args.length; i++) {
       var argument = args[i];
       if (argument.startsWith('--') && argument.length > 2) {
         if (knownOptions.contains(optionName(2, argument))) {
           filtered.add(argument);
         }
       } else if (argument.startsWith('-D') && argument.indexOf('=') > 0) {
         filtered.add(argument);
       }
       if (argument.startsWith('-') && argument.length > 1) {
         if (knownAbbreviations.contains(optionName(1, argument))) {
           filtered.add(argument);
         }
       } else {
         filtered.add(argument);
       }
     }
     return filtered;
   }

   /// Parse [args] into [CommandLineOptions] describing the specified
   /// analyzer options. In case of a format error, calls [printAndFail], which
   /// by default prints an error message to stderr and exits.
   static CommandLineOptions? parse(
       ResourceProvider resourceProvider, List<String> args,
       {void Function(String msg) printAndFail = printAndFail}) {
     var options = _parse(resourceProvider, args);

     /// Only happens in testing.
     if (options == null) {
       return null;
     }

     // Check SDK.
     {
       var sdkPath = options.dartSdkPath;

       // Check that SDK is existing directory.
       if (sdkPath != null) {
         if (!io.Directory(sdkPath).existsSync()) {
           printAndFail('Invalid Dart SDK path: $sdkPath');
           return null; // Only reachable in testing.
         }
       }

       // Infer if unspecified.
       sdkPath ??= getSdkPath();

       var pathContext = resourceProvider.pathContext;
       options.dartSdkPath = file_paths.absoluteNormalized(pathContext, sdkPath);
     }

     return options;
   }

   static String? _absoluteNormalizedPath(
     ResourceProvider resourceProvider,
     String? path,
   ) {
     if (path == null) {
       return null;
     }
     var pathContext = resourceProvider.pathContext;
     return pathContext.normalize(
       pathContext.absolute(path),
     );
   }

   /// Add the standard flags and options to the given [parser]. The standard flags
   /// are those that are typically used to control the way in which the code is
   /// analyzed.
   ///
   // TODO(danrubel): Update DDC to support all the options defined in this method
   // then remove the [ddc] named argument from this method.
   static void _defineAnalysisArguments(ArgParser parser,
       {bool hide = true, bool ddc = false}) {
     parser.addOption(_sdkPathOption,
         help: 'The path to the Dart SDK.', hide: ddc && hide);
     parser.addOption(_analysisOptionsFileOption,
         help: 'Path to an analysis options file.', hide: ddc && hide);
     parser.addMultiOption(_enableExperimentOption,
         help: 'Enable one or more experimental features. If multiple features '
             'are being added, they should be comma separated.',
         splitCommas: true);

     //
     // Hidden flags and options.
     //
     parser.addMultiOption(_defineVariableOption,
         abbr: 'D',
         help:
             'Define an environment declaration. For example, "-Dfoo=bar" defines '
             'an environment declaration named "foo" whose value is "bar".',
         hide: hide);
     parser.addOption(_packagesOption,
         help: 'The path to the package resolution configuration file, which '
             'supplies a mapping of package names\ninto paths.',
         hide: ddc);
     parser.addFlag(_enableInitializingFormalAccessFlag,
         help:
             'Enable support for allowing access to field formal parameters in a '
             'constructor\'s initializer list (deprecated).',
         defaultsTo: false,
         negatable: false,
         hide: hide || ddc);
   }

   static String _getVersion() {
     try {
       // This is relative to bin/snapshot, so ../..
       var versionPath =
           io.Platform.script.resolve('../../version').toFilePath();
       var versionFile = io.File(versionPath);
       return versionFile.readAsStringSync().trim();
     } catch (_) {
       // This happens when the script is not running in the context of an SDK.
       return '<unknown>';
     }
   }

   static CommandLineOptions? _parse(
     ResourceProvider resourceProvider,
     List<String> args,
   ) {
     var verbose = args.contains('-v') || args.contains('--verbose');
     var hide = !verbose;

     var parser = ArgParser(allowTrailingOptions: true);

     if (!hide) {
       parser.addSeparator('General options:');
     }

     // TODO(devoncarew): This defines some hidden flags, which would be better
     // defined with the rest of the hidden flags below (to group well with the
     // other flags).
     _defineAnalysisArguments(parser, hide: hide);

     parser
       ..addOption('format',
           help: 'Specifies the format in which errors are displayed; the only '
               'currently recognized values are \'json\' and \'machine\'.')
       ..addFlag('version',
           help: 'Print the analyzer version.',
           defaultsTo: false,
           negatable: false)
       ..addFlag('help',
           abbr: 'h',
           help:
               'Display this help message. Add --verbose to show hidden options.',
           defaultsTo: false,
           negatable: false)
       ..addFlag('verbose',
           abbr: 'v',
           defaultsTo: false,
           help: 'Verbose output.',
           negatable: false);

     parser.addFlag('color',
         help: 'Use ansi colors when printing messages.',
         defaultsTo: ansi.terminalSupportsAnsi(),
         hide: hide);

     // Hidden flags.
     if (!hide) {
       parser.addSeparator('Less frequently used flags:');
     }

     parser
       ..addFlag('batch',
           help: 'Read commands from standard input (for testing).',
           defaultsTo: false,
           negatable: false,
           hide: hide)
       ..addFlag(_ignoreUnrecognizedFlagsFlag,
           help: 'Ignore unrecognized command line flags.',
           defaultsTo: false,
           negatable: false,
           hide: hide)
       ..addOption(_defaultLanguageVersionOption,
           help: 'The default language version when it is not specified via '
               'other ways (internal, tests only).',
           hide: false)
       ..addFlag('disable-cache-flushing', defaultsTo: false, hide: hide)
       ..addOption('x-perf-report',
           help: 'Writes a performance report to the given file (experimental).',
           hide: hide)
       ..addFlag('enable-conditional-directives',
           help:
               'deprecated -- Enable support for conditional directives (DEP 40).',
           defaultsTo: false,
           negatable: false,
           hide: hide)
       ..addFlag('log',
           help: 'Log additional messages and exceptions.',
           defaultsTo: false,
           negatable: false,
           hide: hide)
       ..addFlag('use-analysis-driver-memory-byte-store',
           help: 'Use memory byte store, not the file system cache.',
           defaultsTo: false,
           negatable: false,
           hide: hide)
       ..addMultiOption('url-mapping',
           help: '--url-mapping=libraryUri,/path/to/library.dart directs the '
               'analyzer to use "library.dart" as the source for an import '
               'of "libraryUri".',
           splitCommas: false,
           hide: hide)
       ..addFlag('train-snapshot',
           help: 'Analyze the given source for the purposes of training a '
               'dartanalyzer snapshot.',
           hide: hide,
           negatable: false);

     try {
       if (args.contains('--$_ignoreUnrecognizedFlagsFlag')) {
         args = filterUnknownArguments(args, parser);
       }
       var results = parser.parse(args);

       // Help requests.
       if (cast(results['help'])) {
         _showUsage(parser, fromHelp: true);
         exitHandler(0);
         return null; // Only reachable in testing.
       }

       // Batch mode and input files.
       if (cast(results['batch'])) {
         if (results.rest.isNotEmpty) {
           errorSink.writeln('No source files expected in the batch mode.');
           _showUsage(parser);
           exitHandler(15);
           return null; // Only reachable in testing.
         }
       } else if (cast(results['version'])) {
         outSink.writeln('$_binaryName version ${_getVersion()}');
         exitHandler(0);
         return null; // Only reachable in testing.
       } else {
         if (results.rest.isEmpty) {
           _showUsage(parser, fromHelp: true);
           exitHandler(15);
           return null; // Only reachable in testing.
         }
       }

       if (results.wasParsed(_enableExperimentOption)) {
         var names =
             (results[_enableExperimentOption] as List).cast<String>().toList();
         var errorFound = false;
         for (var validationResult in validateFlags(names)) {
           if (validationResult.isError) {
             errorFound = true;
           }
           var kind = validationResult.isError ? 'ERROR' : 'WARNING';
           errorSink.writeln('$kind: ${validationResult.message}');
         }
         if (errorFound) {
           _showUsage(parser);
           exitHandler(15);
           return null; // Only reachable in testing.
         }
       }

       return CommandLineOptions._fromArgs(resourceProvider, results);
     } on FormatException catch (e) {
       errorSink.writeln(e.message);
       _showUsage(parser);
       exitHandler(15);
       return null; // Only reachable in testing.
     }
   }

   static void _showUsage(ArgParser parser, {bool fromHelp = false}) {
     errorSink.writeln(
         'Usage: $_binaryName [options...] <directory or list of files>');

     errorSink.writeln('');
     errorSink.writeln(parser.usage);

     errorSink.writeln('');
     errorSink.writeln('''
 Run "dartanalyzer -h -v" for verbose help output, including less commonly used options.
 For more information, see https://dart.dev/tools/dartanalyzer.\n''');
   }
 }
	// Copyright (c) 2015, 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:io' as io;

	import 'package:analyzer/dart/analysis/features.dart';
	import 'package:analyzer/file_system/file_system.dart';
	import 'package:analyzer/src/dart/analysis/experiments.dart';
	import 'package:analyzer/src/generated/engine.dart' show AnalysisOptionsImpl;
	import 'package:analyzer/src/util/file_paths.dart' as file_paths;
	import 'package:analyzer/src/util/sdk.dart';
	import 'package:analyzer_cli/src/ansi.dart' as ansi;
	import 'package:analyzer_cli/src/driver.dart';
	import 'package:args/args.dart';
	import 'package:pub_semver/pub_semver.dart';

	const _analysisOptionsFileOption = 'options';
	const _binaryName = 'dartanalyzer';
	const _defaultLanguageVersionOption = 'default-language-version';
	const _defineVariableOption = 'D';
	const _enableExperimentOption = 'enable-experiment';
	const _enableInitializingFormalAccessFlag = 'initializing-formal-access';
	const _ignoreUnrecognizedFlagsFlag = 'ignore-unrecognized-flags';
	const _packagesOption = 'packages';
	const _sdkPathOption = 'dart-sdk';

	/// Shared exit handler.
	///
	/// Visible for testing.
	ExitHandler exitHandler = io.exit;

	T cast<T>(dynamic value) => value as T;

	T? castNullable<T>(dynamic value) => value as T?;

	/// Print the given [message] to stderr and exit with the given [exitCode].
	void printAndFail(String message, {int exitCode = 15}) {
	errorSink.writeln(message);
	exitHandler(exitCode);
	}

	/// Exit handler.
	///
	/// Visible for testing.
	typedef ExitHandler = void Function(int code);

	/// Analyzer commandline configuration options.
	class CommandLineOptions {
	final ArgResults _argResults;

	/// The file path of the analysis options file that should be used in place of
	/// any file in the root directory or a parent of the root directory,
	/// or `null` if the normal lookup mechanism should be used.
	String? defaultAnalysisOptionsPath;

	/// The file path of the .packages file that should be used in place of any
	/// file found using the normal (Package Specification DEP) lookup mechanism,
	/// or `null` if the normal lookup mechanism should be used.
	String? defaultPackagesPath;

	/// A table mapping variable names to values for the declared variables.
	final Map<String, String> declaredVariables = {};

	/// The path to the dart SDK.
	String? dartSdkPath;

	/// Whether to disable cache flushing. This option can improve analysis
	/// speed at the expense of memory usage. It may also be useful for working
	/// around bugs.
	final bool disableCacheFlushing;

	/// Whether to display version information
	final bool displayVersion;

	/// Whether to ignore unrecognized flags
	final bool ignoreUnrecognizedFlags;

	/// Whether to log additional analysis messages and exceptions
	final bool log;

	/// Whether to use 'json' format for error display
	final bool jsonFormat;

	/// Whether to use 'machine' format for error display
	final bool machineFormat;

	/// The path to a file to write a performance log.
	/// (Or null if not enabled.)
	final String? perfReport;

	/// Batch mode (for unit testing)
	final bool batchMode;

	/// The source files to analyze
	final List<String> sourceFiles;

	/// Emit output in a verbose mode.
	final bool verbose;

	/// Use ANSI color codes for output.
	final bool color;

	/// Whether we should analyze the given source for the purposes of training a
	/// Dart analyzer snapshot.
	final bool trainSnapshot;

	/// Initialize options from the given parsed [args].
	CommandLineOptions._fromArgs(
	ResourceProvider resourceProvider,
	ArgResults args,
	) : _argResults = args,
	dartSdkPath = castNullable(args[_sdkPathOption]),
	disableCacheFlushing = cast(args['disable-cache-flushing']),
	displayVersion = cast(args['version']),
	ignoreUnrecognizedFlags = cast(args[_ignoreUnrecognizedFlagsFlag]),
	log = cast(args['log']),
	jsonFormat = args['format'] == 'json',
	machineFormat = args['format'] == 'machine',
	perfReport = castNullable(args['x-perf-report']),
	batchMode = cast(args['batch']),
	sourceFiles = args.rest,
	trainSnapshot = cast(args['train-snapshot']),
	verbose = cast(args['verbose']),
	color = cast(args['color']) {
	//
	// File locations.
	//
	defaultAnalysisOptionsPath = _absoluteNormalizedPath(
	resourceProvider,
	castNullable(args[_analysisOptionsFileOption]),
	);
	defaultPackagesPath = _absoluteNormalizedPath(
	resourceProvider,
	castNullable(args[_packagesOption]),
	);

	//
	// Declared variables.
	//
	var variables = (args[_defineVariableOption] as List).cast<String>();
	for (var variable in variables) {
	var index = variable.indexOf('=');
	if (index < 0) {
	// TODO(brianwilkerson): Decide the semantics we want in this case.
	// The VM prints "No value given to -D option", then tries to load '-Dfoo'
	// as a file and dies. Unless there was nothing after the '-D', in which
	// case it prints the warning and ignores the option.
	} else {
	var name = variable.substring(0, index);
	if (name.isNotEmpty) {
	// TODO(brianwilkerson): Decide the semantics we want in the case where
	// there is no name. If there is no name, the VM tries to load a file
	// named '-D' and dies.
	declaredVariables[name] = variable.substring(index + 1);
	}
	}
	}
	}

	/// The default language version for files that are not in a package.
	/// (Or null if no default language version to force.)
	String? get defaultLanguageVersion {
	return castNullable(_argResults[_defaultLanguageVersionOption]);
	}

	/// A list of the names of the experiments that are to be enabled.
	List<String>? get enabledExperiments {
	return castNullable(_argResults[_enableExperimentOption]);
	}

	/// Update the [analysisOptions] with flags that the user specified
	/// explicitly. The [analysisOptions] are usually loaded from one of
	/// `analysis_options.yaml` files, possibly with includes. We consider
	/// flags that the user specified as command line options more important,
	/// so override the corresponding options.
	void updateAnalysisOptions(AnalysisOptionsImpl analysisOptions) {
	var defaultLanguageVersion = this.defaultLanguageVersion;
	if (defaultLanguageVersion != null) {
	var nonPackageLanguageVersion =
	Version.parse('$defaultLanguageVersion.0');
	analysisOptions.nonPackageLanguageVersion = nonPackageLanguageVersion;
	analysisOptions.nonPackageFeatureSet = FeatureSet.latestLanguageVersion()
	.restrictToVersion(nonPackageLanguageVersion);
	}

	var enabledExperiments = this.enabledExperiments!;
	if (enabledExperiments.isNotEmpty) {
	analysisOptions.contextFeatures = FeatureSet.fromEnableFlags2(
	sdkLanguageVersion: ExperimentStatus.currentVersion,
	flags: enabledExperiments,
	);
	}
	}

	/// Return a list of command-line arguments containing all of the given [args]
	/// that are defined by the given [parser]. An argument is considered to be
	/// defined by the parser if
	/// - it starts with '--' and the rest of the argument (minus any value
	/// introduced by '=') is the name of a known option,
	/// - it starts with '-' and the rest of the argument (minus any value
	/// introduced by '=') is the name of a known abbreviation, or
	/// - it starts with something other than '--' or '-'.
	///
	/// This function allows command-line tools to implement the
	/// '--ignore-unrecognized-flags' option.
	static List<String> filterUnknownArguments(
	List<String> args, ArgParser parser) {
	var knownOptions = <String>{};
	var knownAbbreviations = <String>{};
	parser.options.forEach((String name, Option option) {
	knownOptions.add(name);
	var abbreviation = option.abbr;
	if (abbreviation != null) {
	knownAbbreviations.add(abbreviation);
	}
	if (option.negatable ?? false) {
	knownOptions.add('no-$name');
	}
	});
	String optionName(int prefixLength, String argument) {
	var equalsOffset = argument.lastIndexOf('=');
	if (equalsOffset < 0) {
	return argument.substring(prefixLength);
	}
	return argument.substring(prefixLength, equalsOffset);
	}

	var filtered = <String>[];
	for (var i = 0; i < args.length; i++) {
	var argument = args[i];
	if (argument.startsWith('--') && argument.length > 2) {
	if (knownOptions.contains(optionName(2, argument))) {
	filtered.add(argument);
	}
	} else if (argument.startsWith('-D') && argument.indexOf('=') > 0) {
	filtered.add(argument);
	}
	if (argument.startsWith('-') && argument.length > 1) {
	if (knownAbbreviations.contains(optionName(1, argument))) {
	filtered.add(argument);
	}
	} else {
	filtered.add(argument);
	}
	}
	return filtered;
	}

	/// Parse [args] into [CommandLineOptions] describing the specified
	/// analyzer options. In case of a format error, calls [printAndFail], which
	/// by default prints an error message to stderr and exits.
	static CommandLineOptions? parse(
	ResourceProvider resourceProvider, List<String> args,
	{void Function(String msg) printAndFail = printAndFail}) {
	var options = _parse(resourceProvider, args);

	/// Only happens in testing.
	if (options == null) {
	return null;
	}

	// Check SDK.
	{
	var sdkPath = options.dartSdkPath;

	// Check that SDK is existing directory.
	if (sdkPath != null) {
	if (!io.Directory(sdkPath).existsSync()) {
	printAndFail('Invalid Dart SDK path: $sdkPath');
	return null; // Only reachable in testing.
	}
	}

	// Infer if unspecified.
	sdkPath ??= getSdkPath();

	var pathContext = resourceProvider.pathContext;
	options.dartSdkPath = file_paths.absoluteNormalized(pathContext, sdkPath);
	}

	return options;
	}

	static String? _absoluteNormalizedPath(
	ResourceProvider resourceProvider,
	String? path,
	) {
	if (path == null) {
	return null;
	}
	var pathContext = resourceProvider.pathContext;
	return pathContext.normalize(
	pathContext.absolute(path),
	);
	}

	/// Add the standard flags and options to the given [parser]. The standard flags
	/// are those that are typically used to control the way in which the code is
	/// analyzed.
	///
	// TODO(danrubel): Update DDC to support all the options defined in this method
	// then remove the [ddc] named argument from this method.
	static void _defineAnalysisArguments(ArgParser parser,
	{bool hide = true, bool ddc = false}) {
	parser.addOption(_sdkPathOption,
	help: 'The path to the Dart SDK.', hide: ddc && hide);
	parser.addOption(_analysisOptionsFileOption,
	help: 'Path to an analysis options file.', hide: ddc && hide);
	parser.addMultiOption(_enableExperimentOption,
	help: 'Enable one or more experimental features. If multiple features '
	'are being added, they should be comma separated.',
	splitCommas: true);

	//
	// Hidden flags and options.
	//
	parser.addMultiOption(_defineVariableOption,
	abbr: 'D',
	help:
	'Define an environment declaration. For example, "-Dfoo=bar" defines '
	'an environment declaration named "foo" whose value is "bar".',
	hide: hide);
	parser.addOption(_packagesOption,
	help: 'The path to the package resolution configuration file, which '
	'supplies a mapping of package names\ninto paths.',
	hide: ddc);
	parser.addFlag(_enableInitializingFormalAccessFlag,
	help:
	'Enable support for allowing access to field formal parameters in a '
	'constructor\'s initializer list (deprecated).',
	defaultsTo: false,
	negatable: false,
	hide: hide \|\| ddc);
	}

	static String _getVersion() {
	try {
	// This is relative to bin/snapshot, so ../..
	var versionPath =
	io.Platform.script.resolve('../../version').toFilePath();
	var versionFile = io.File(versionPath);
	return versionFile.readAsStringSync().trim();
	} catch (_) {
	// This happens when the script is not running in the context of an SDK.
	return '<unknown>';
	}
	}

	static CommandLineOptions? _parse(
	ResourceProvider resourceProvider,
	List<String> args,
	) {
	var verbose = args.contains('-v') \|\| args.contains('--verbose');
	var hide = !verbose;

	var parser = ArgParser(allowTrailingOptions: true);

	if (!hide) {
	parser.addSeparator('General options:');
	}

	// TODO(devoncarew): This defines some hidden flags, which would be better
	// defined with the rest of the hidden flags below (to group well with the
	// other flags).
	_defineAnalysisArguments(parser, hide: hide);

	parser
	..addOption('format',
	help: 'Specifies the format in which errors are displayed; the only '
	'currently recognized values are \'json\' and \'machine\'.')
	..addFlag('version',
	help: 'Print the analyzer version.',
	defaultsTo: false,
	negatable: false)
	..addFlag('help',
	abbr: 'h',
	help:
	'Display this help message. Add --verbose to show hidden options.',
	defaultsTo: false,
	negatable: false)
	..addFlag('verbose',
	abbr: 'v',
	defaultsTo: false,
	help: 'Verbose output.',
	negatable: false);

	parser.addFlag('color',
	help: 'Use ansi colors when printing messages.',
	defaultsTo: ansi.terminalSupportsAnsi(),
	hide: hide);

	// Hidden flags.
	if (!hide) {
	parser.addSeparator('Less frequently used flags:');
	}

	parser
	..addFlag('batch',
	help: 'Read commands from standard input (for testing).',
	defaultsTo: false,
	negatable: false,
	hide: hide)
	..addFlag(_ignoreUnrecognizedFlagsFlag,
	help: 'Ignore unrecognized command line flags.',
	defaultsTo: false,
	negatable: false,
	hide: hide)
	..addOption(_defaultLanguageVersionOption,
	help: 'The default language version when it is not specified via '
	'other ways (internal, tests only).',
	hide: false)
	..addFlag('disable-cache-flushing', defaultsTo: false, hide: hide)
	..addOption('x-perf-report',
	help: 'Writes a performance report to the given file (experimental).',
	hide: hide)
	..addFlag('enable-conditional-directives',
	help:
	'deprecated -- Enable support for conditional directives (DEP 40).',
	defaultsTo: false,
	negatable: false,
	hide: hide)
	..addFlag('log',
	help: 'Log additional messages and exceptions.',
	defaultsTo: false,
	negatable: false,
	hide: hide)
	..addFlag('use-analysis-driver-memory-byte-store',
	help: 'Use memory byte store, not the file system cache.',
	defaultsTo: false,
	negatable: false,
	hide: hide)
	..addMultiOption('url-mapping',
	help: '--url-mapping=libraryUri,/path/to/library.dart directs the '
	'analyzer to use "library.dart" as the source for an import '
	'of "libraryUri".',
	splitCommas: false,
	hide: hide)
	..addFlag('train-snapshot',
	help: 'Analyze the given source for the purposes of training a '
	'dartanalyzer snapshot.',
	hide: hide,
	negatable: false);

	try {
	if (args.contains('--$_ignoreUnrecognizedFlagsFlag')) {
	args = filterUnknownArguments(args, parser);
	}
	var results = parser.parse(args);

	// Help requests.
	if (cast(results['help'])) {
	_showUsage(parser, fromHelp: true);
	exitHandler(0);
	return null; // Only reachable in testing.
	}

	// Batch mode and input files.
	if (cast(results['batch'])) {
	if (results.rest.isNotEmpty) {
	errorSink.writeln('No source files expected in the batch mode.');
	_showUsage(parser);
	exitHandler(15);
	return null; // Only reachable in testing.
	}
	} else if (cast(results['version'])) {
	outSink.writeln('$_binaryName version ${_getVersion()}');
	exitHandler(0);
	return null; // Only reachable in testing.
	} else {
	if (results.rest.isEmpty) {
	_showUsage(parser, fromHelp: true);
	exitHandler(15);
	return null; // Only reachable in testing.
	}
	}

	if (results.wasParsed(_enableExperimentOption)) {
	var names =
	(results[_enableExperimentOption] as List).cast<String>().toList();
	var errorFound = false;
	for (var validationResult in validateFlags(names)) {
	if (validationResult.isError) {
	errorFound = true;
	}
	var kind = validationResult.isError ? 'ERROR' : 'WARNING';
	errorSink.writeln('$kind: ${validationResult.message}');
	}
	if (errorFound) {
	_showUsage(parser);
	exitHandler(15);
	return null; // Only reachable in testing.
	}
	}

	return CommandLineOptions._fromArgs(resourceProvider, results);
	} on FormatException catch (e) {
	errorSink.writeln(e.message);
	_showUsage(parser);
	exitHandler(15);
	return null; // Only reachable in testing.
	}
	}

	static void _showUsage(ArgParser parser, {bool fromHelp = false}) {
	errorSink.writeln(
	'Usage: $_binaryName [options...] <directory or list of files>');

	errorSink.writeln('');
	errorSink.writeln(parser.usage);

	errorSink.writeln('');
	errorSink.writeln('''
	Run "dartanalyzer -h -v" for verbose help output, including less commonly used options.
	For more information, see https://dart.dev/tools/dartanalyzer.\n''');
	}
	}