pkgs/package_config/bin/package_config_of.dart - tools.git - Git at Google

 #! /bin/env dart
 // Copyright (c) 2025, 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.

 /// Utility for checking which package configuration applies to a specific file
 /// or path.
 library;

 import 'dart:convert';
 import 'dart:io';

 import 'package:package_config/package_config.dart';
 import 'package:path/path.dart' as p;

 /// Output modes.
 const _printText = 0;
 const _printJsonLines = 1;
 const _printJsonList = 2;

 void main(List<String> args) async {
   // Basic command line parser. No fancy.
   var files = <String>[];
   var stopAtPubspec = false;
   var noParent = false;
   var hasPrintedUsage = false;
   var parseFlags = true;
   var printFormat = _printText;
   for (var arg in args) {
     if (parseFlags && arg.startsWith('-')) {
       switch (arg) {
         case '-b':
           noParent = true;
         case '-g':
           stopAtPubspec = false;
         case '-h':
           if (!hasPrintedUsage) {
             hasPrintedUsage = true;
             stdout.writeln(usage);
           }
         case '-j':
           printFormat = _printJsonLines;
         case '-jl':
           printFormat = _printJsonList;
         case '-p':
           stopAtPubspec = true;
         case '--':
           parseFlags = false;
         default:
           stderr.writeln('Unexpected flag: $arg');
           if (!hasPrintedUsage) {
             hasPrintedUsage = true;
             stderr.writeln(usage);
           }
       }
     } else {
       files.add(arg);
     }
   }
   if (hasPrintedUsage) return;

   /// Check current directory if no PATHs on command line.
   if (files.isEmpty) {
     files.add(p.current);
   }

   var loader = PackageConfigLoader(
     stopAtPubspec: stopAtPubspec,
     noParent: noParent,
   );

   // Collects infos if printing as single JSON value.
   // Otherwise prints output for each file as soon as it's available.
   var jsonList = <Map<String, Object?>>[];

   for (var arg in files) {
     var fileInfo = await _resolveInfo(arg, loader);
     if (fileInfo == null) continue; // File does not exist, already reported.
     if (printFormat == _printText) {
       // Display as "readable" text.
       print(fileInfo);
     } else if (printFormat == _printJsonLines) {
       // Write JSON on a single line.
       stdout.writeln(
         const JsonEncoder.withIndent(null).convert(fileInfo.toJson()),
       );
     } else {
       // Store JSON in list, print entire list later.
       assert(printFormat == _printJsonList);
       jsonList.add(fileInfo.toJson());
     }
   }
   if (printFormat == _printJsonList) {
     stdout.writeln(const JsonEncoder.withIndent('  ').convert(jsonList));
   }
 }

 /// Finds package information for command line provided path.
 Future<ConfigInfo?> _resolveInfo(String arg, PackageConfigLoader loader) async {
   var path = p.normalize(arg);
   var file = File(path);
   if (file.existsSync()) {
     file = file.absolute;
     var directory = Directory(p.dirname(file.path));
     return await _resolvePackageConfig(directory, file, loader);
   }
   var directory = Directory(path);
   if (directory.existsSync()) {
     return await _resolvePackageConfig(directory.absolute, null, loader);
   }
   stderr.writeln('Cannot find file or directory: $arg');
   return null;
 }

 // --------------------------------------------------------------------
 // Convert package configuration information to a simple model object.

 /// Extract package configuration information for a file from a configuration.
 Future<ConfigInfo> _resolvePackageConfig(
   Directory path,
   File? file,
   PackageConfigLoader loader,
 ) async {
   var originPath = path.path;
   var targetPath = file?.path ?? originPath;
   var (configPath, config) = await loader.findPackageConfig(originPath);
   Package? package;
   Uri? packageUri;
   LanguageVersion? overrideVersion;
   if (config != null) {
     var uri = file?.uri ?? path.uri;
     package = config.packageOf(uri);
     if (package != null) {
       packageUri = config.toPackageUri(uri);
     }
   }
   if (file != null) {
     overrideVersion = _readOverrideVersion(file);
   }
   return ConfigInfo(
     targetPath,
     configPath,
     package,
     packageUri,
     overrideVersion,
   );
 }

 /// Gathered package configuration information for [path].
 final class ConfigInfo {
   /// Original path being resolved.
   final String path;

   /// Path to package configuration file, if any.
   final String? configPath;

   /// Package that path belongs to, if any.
   final Package? package;

   /// Package URI for [path], if it has one.
   /// Always `null` if [package] is `null`.
   final Uri? packageUri;

   /// Language version override in file, if any.
   final LanguageVersion? languageVersionOverride;

   ConfigInfo(
     this.path,
     this.configPath,
     this.package,
     this.packageUri,
     this.languageVersionOverride,
   );

   Map<String, Object?> toJson() {
     return {
       JsonKey.path: path,
       if (configPath != null) JsonKey.configPath: configPath,
       if (package case var package?)
         JsonKey.package: {
           JsonKey.name: package.name,
           JsonKey.root: _fileUriPath(package.root),
           if (package.languageVersion case var languageVersion?)
             JsonKey.languageVersion: languageVersion.toString(),
           if (packageUri case var packageUri?) ...{
             JsonKey.packageUri: packageUri.toString(),
             if (package.root != package.packageUriRoot)
               JsonKey.lib: _fileUriPath(package.packageUriRoot),
           },
         },
       if (languageVersionOverride case var override?)
         JsonKey.languageVersionOverride: override.toString(),
     };
   }

   /// Package configuration information for a path in a readable format.
   @override
   String toString() {
     var buffer = StringBuffer();
     var sep = Platform.pathSeparator;
     var kind = path.endsWith(Platform.pathSeparator) ? 'directory' : 'file';
     buffer.writeln('Package configuration for $kind: ${p.relative(path)}');
     if (configPath case var configPath?) {
       buffer.writeln('- Package configuration: ${p.relative(configPath)}');
       if (package case var package?) {
         buffer.writeln('- In package: ${package.name}');
         if (package.languageVersion case var version?) {
           buffer.writeln('  - default language version: $version');
         }
         var rootUri = _fileUriPath(package.root);
         var rootPath = p.relative(Directory.fromUri(Uri.parse(rootUri)).path);
         buffer.writeln('  - with root: $rootPath$sep');
         if (packageUri case var packageUri?) {
           buffer.writeln('  - Has package URI: $packageUri');
           if (package.root != package.packageUriRoot) {
             var libPath = p.relative(
               Directory.fromUri(package.packageUriRoot).path,
             );
             buffer.writeln('    - relative to: $libPath$sep');
           } else {
             buffer.writeln('    - relative to root');
           }
         }
       } else {
         buffer.writeln('- Is not part of any package');
       }
     } else {
       buffer.writeln('- No package configuration found');
       assert(package == null);
     }
     if (languageVersionOverride case var override?) {
       buffer.writeln('- Language version override: // @dart=$override');
     }
     return buffer.toString();
   }

   static String _fileUriPath(Uri uri) {
     assert(uri.isScheme('file'));
     return File.fromUri(uri).path;
   }
 }

 // Constants for all used JSON keys to prevent mis-typing.
 extension type const JsonKey(String value) implements String {
   static const JsonKey path = JsonKey('path');
   static const JsonKey configPath = JsonKey('configPath');
   static const JsonKey package = JsonKey('package');
   static const JsonKey name = JsonKey('name');
   static const JsonKey root = JsonKey('root');
   static const JsonKey packageUri = JsonKey('packageUri');
   static const JsonKey lib = JsonKey('lib');
   static const JsonKey languageVersion = JsonKey('languageVersion');
   static const JsonKey languageVersionOverride = JsonKey(
     'languageVersionOverride',
   );
 }

 // --------------------------------------------------------------------
 // Find language version override marker in file.

 /// Tries to find a language override marker in a Dart file.
 ///
 /// Uses a best-effort approach to scan for a line
 /// of the form `// @dart=X.Y` before any Dart directive.
 /// Any consistently and idiomatically formatted file will be recognized
 /// correctly. A file with a multiline `/*...*/` comment where
 /// internal lines do not start with `*`, or where a Dart directive
 /// follows a `*/` on the same line, may be misinterpreted.
 LanguageVersion? _readOverrideVersion(File file) {
   String fileContent;
   try {
     fileContent = file.readAsStringSync();
   } catch (e) {
     stderr
       ..writeln('Error reading ${file.path} as UTF-8 text:')
       ..writeln(e);
     return null;
   }
   // Skip BOM only at start.
   const bom = '\uFEFF';
   var contentStart = 0;
   // Skip BOM only at start.
   if (fileContent.startsWith(bom)) contentStart = 1;
   // Skip `#! ...` line only at start.
   if (fileContent.startsWith('#!', contentStart)) {
     // Skip until end-of-line, whether ended by `\n` or `\r\n`.
     var endOfHashBang = fileContent.indexOf('\n', contentStart + 2);
     if (endOfHashBang < 0) return null; // No EOL after `#!`.
     contentStart = endOfHashBang + 1;
   }
   // Match lines until one that looks like a version override or not a comment.
   for (var match in leadRegExp.allMatches(fileContent, contentStart)) {
     if (match.namedGroup('major') case var major?) {
       // Found `// @dart=<major>.<minor>` line.
       var minor = match.namedGroup('minor')!;
       return LanguageVersion(int.parse(major), int.parse(minor));
     } else if (match.namedGroup('other') != null) {
       // Found non-comment, so too late for language version markers.
       break;
     }
   }
   return null;
 }

 /// Heuristic scanner for finding leading comment lines.
 ///
 /// Finds leading comments and any language version override marker
 /// within them.
 ///
 /// Accepts empty lines or lines starting with `/*`, `*` or `//` as
 /// initial comment lines, and any other non-space/tab first character
 /// as a non-comment, which ends the section
 /// that can contain language overrides.
 ///
 /// It's possible to construct files where that's not correct, fx.
 /// ```
 /// /* something */ import "banana.dart";
 /// // @dart=2.14
 /// ```
 /// To be absolutely certain, the code would need to properly tokenize
 /// *nested* comments, which is not a job for a RegExp.
 /// This RegExp should work for well-behaved and -formatted files.
 final leadRegExp = RegExp(
   r'^[ \t]*'
   r'(?:'
   r'$' // Empty line
   r'|'
   r'/?\*' // Line starting with `/*` or `*`, assumed a comment continuation.
   r'|'
   // Line starting with `//`, and possibly followed by language override.
   r'//(?: *@ *dart *= *(?<major>\d+) *\. *(?<minor>\d+) *$)?'
   r'|'
   r'(?<other>[^ \t/*])' // Any other line, assumed to end initial comments.
   r')',
   multiLine: true,
 );

 // --------------------------------------------------------------------
 // Find and load (and cache) package configurations

 class PackageConfigLoader {
   /// Stop searching at the current working directory.
   final bool noParent;

   /// Stop searching if finding a `pubspec.yaml` with no package configuration.
   final bool stopAtPubspec;

   /// Cache lookup results in case someone does more lookups on the same path.
   final Map<
     (String path, bool stopAtPubspec),
     (String? configPath, PackageConfig? config)
   >
   _packageConfigCache = {};

   PackageConfigLoader({this.stopAtPubspec = false, this.noParent = false});

   /// Finds a package configuration relative to [path].
   ///
   /// Caches result for each directory looked at.
   /// If someone does multiple lookups in the same directory, there is no need
   /// to find and parse the same configuration more than once.
   Future<(String? path, PackageConfig? config)> findPackageConfig(
     String path,
   ) async =>
       _packageConfigCache[(
         path,
         stopAtPubspec,
       )] ??= await _findPackageConfigNoCache(path);

   Future<(String? path, PackageConfig? config)> _findPackageConfigNoCache(
     String path,
   ) async {
     var configPath = p.join(path, '.dart_tool', 'package_config.json');
     var configFile = File(configPath);
     if (configFile.existsSync()) {
       var hasError = false;
       var config = await loadPackageConfig(
         configFile.absolute,
         onError: (error) {
           stderr.writeln(
             'Error parsing package configuration config ($configPath):\n'
             ' $error',
           );
           hasError = true;
         },
       );
       return (configPath, hasError ? null : config);
     }
     if (stopAtPubspec) {
       var pubspecPath = p.join(path, 'pubspec.yaml');
       var pubspecFile = File(pubspecPath);
       if (pubspecFile.existsSync()) {
         stderr
           ..writeln('Found pubspec.yaml with no .dart_tool/package_config.json')
           ..writeln('  at $path');
         return (null, null);
       }
     }
     if (noParent && path == p.current) return (null, null);
     var parentPath = p.dirname(path);
     if (parentPath == path) return (null, null);
     // Recurse on parent path.
     return findPackageConfig(parentPath);
   }
 }

 const String usage = '''
 Usage: dart package_config_of.dart [-p|-j|-jl|-h] PATH*

 Searches from (each) PATH for a `.dart_tool/package_config.json` file,
 loads that, and prints information about that package configuration
 and the configuration for PATH in it.
 If no PATH is given, the current directory is used.

 Flags:
   -p    : Stop when finding a 'pubspec.yaml' file without a package config.
           The default is to ignore `pubspec.yaml` files and only look for
           `.dart_tool/package_config.json` files, which will work correctly
           for Pub workspaces.
   -b    : Stop if reaching the current working directory.
           When looking for a package configuration, don't try further out
           than the current directory.
           Only works for starting PATHs inside the current directory.
   -j    : Output as JSON. Emits a single JSON object for each file, on
           a line of its own (JSON-lines format). See format below.
           Default is to output human readable text.
   -jl   : Emits as a single JSON list containing the JSON outputs.
           See format of individual elements below.
           Default is to output human readable text.
   -h    : Print this help text. Ignore any PATHs.

 A JSON object written using -j or -jl has following entries:
     "path": "PATH", normalized and ends in a `/` if a directory.
     "configPath": path to config file. Omitted if no or invalid config.
     "package": The package that PATH belongs to, if any. A map with:
         "name": Package name.
         "root": Path to package root.
         "languageVersion": "A.B", default language version for package.
         "packageUri": The package: URI of PATH, if one exists.
         "lib": If package URI exists, the package URI root,
                unless it's the same as the package root.
     "languageVersionOverride": "A.B", if file has '//@dart=' version override.
 ''';
	#! /bin/env dart
	// Copyright (c) 2025, 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.

	/// Utility for checking which package configuration applies to a specific file
	/// or path.
	library;

	import 'dart:convert';
	import 'dart:io';

	import 'package:package_config/package_config.dart';
	import 'package:path/path.dart' as p;

	/// Output modes.
	const _printText = 0;
	const _printJsonLines = 1;
	const _printJsonList = 2;

	void main(List<String> args) async {
	// Basic command line parser. No fancy.
	var files = <String>[];
	var stopAtPubspec = false;
	var noParent = false;
	var hasPrintedUsage = false;
	var parseFlags = true;
	var printFormat = _printText;
	for (var arg in args) {
	if (parseFlags && arg.startsWith('-')) {
	switch (arg) {
	case '-b':
	noParent = true;
	case '-g':
	stopAtPubspec = false;
	case '-h':
	if (!hasPrintedUsage) {
	hasPrintedUsage = true;
	stdout.writeln(usage);
	}
	case '-j':
	printFormat = _printJsonLines;
	case '-jl':
	printFormat = _printJsonList;
	case '-p':
	stopAtPubspec = true;
	case '--':
	parseFlags = false;
	default:
	stderr.writeln('Unexpected flag: $arg');
	if (!hasPrintedUsage) {
	hasPrintedUsage = true;
	stderr.writeln(usage);
	}
	}
	} else {
	files.add(arg);
	}
	}
	if (hasPrintedUsage) return;

	/// Check current directory if no PATHs on command line.
	if (files.isEmpty) {
	files.add(p.current);
	}

	var loader = PackageConfigLoader(
	stopAtPubspec: stopAtPubspec,
	noParent: noParent,
	);

	// Collects infos if printing as single JSON value.
	// Otherwise prints output for each file as soon as it's available.
	var jsonList = <Map<String, Object?>>[];

	for (var arg in files) {
	var fileInfo = await _resolveInfo(arg, loader);
	if (fileInfo == null) continue; // File does not exist, already reported.
	if (printFormat == _printText) {
	// Display as "readable" text.
	print(fileInfo);
	} else if (printFormat == _printJsonLines) {
	// Write JSON on a single line.
	stdout.writeln(
	const JsonEncoder.withIndent(null).convert(fileInfo.toJson()),
	);
	} else {
	// Store JSON in list, print entire list later.
	assert(printFormat == _printJsonList);
	jsonList.add(fileInfo.toJson());
	}
	}
	if (printFormat == _printJsonList) {
	stdout.writeln(const JsonEncoder.withIndent(' ').convert(jsonList));
	}
	}

	/// Finds package information for command line provided path.
	Future<ConfigInfo?> _resolveInfo(String arg, PackageConfigLoader loader) async {
	var path = p.normalize(arg);
	var file = File(path);
	if (file.existsSync()) {
	file = file.absolute;
	var directory = Directory(p.dirname(file.path));
	return await _resolvePackageConfig(directory, file, loader);
	}
	var directory = Directory(path);
	if (directory.existsSync()) {
	return await _resolvePackageConfig(directory.absolute, null, loader);
	}
	stderr.writeln('Cannot find file or directory: $arg');
	return null;
	}

	// --------------------------------------------------------------------
	// Convert package configuration information to a simple model object.

	/// Extract package configuration information for a file from a configuration.
	Future<ConfigInfo> _resolvePackageConfig(
	Directory path,
	File? file,
	PackageConfigLoader loader,
	) async {
	var originPath = path.path;
	var targetPath = file?.path ?? originPath;
	var (configPath, config) = await loader.findPackageConfig(originPath);
	Package? package;
	Uri? packageUri;
	LanguageVersion? overrideVersion;
	if (config != null) {
	var uri = file?.uri ?? path.uri;
	package = config.packageOf(uri);
	if (package != null) {
	packageUri = config.toPackageUri(uri);
	}
	}
	if (file != null) {
	overrideVersion = _readOverrideVersion(file);
	}
	return ConfigInfo(
	targetPath,
	configPath,
	package,
	packageUri,
	overrideVersion,
	);
	}

	/// Gathered package configuration information for [path].
	final class ConfigInfo {
	/// Original path being resolved.
	final String path;

	/// Path to package configuration file, if any.
	final String? configPath;

	/// Package that path belongs to, if any.
	final Package? package;

	/// Package URI for [path], if it has one.
	/// Always `null` if [package] is `null`.
	final Uri? packageUri;

	/// Language version override in file, if any.
	final LanguageVersion? languageVersionOverride;

	ConfigInfo(
	this.path,
	this.configPath,
	this.package,
	this.packageUri,
	this.languageVersionOverride,
	);

	Map<String, Object?> toJson() {
	return {
	JsonKey.path: path,
	if (configPath != null) JsonKey.configPath: configPath,
	if (package case var package?)
	JsonKey.package: {
	JsonKey.name: package.name,
	JsonKey.root: _fileUriPath(package.root),
	if (package.languageVersion case var languageVersion?)
	JsonKey.languageVersion: languageVersion.toString(),
	if (packageUri case var packageUri?) ...{
	JsonKey.packageUri: packageUri.toString(),
	if (package.root != package.packageUriRoot)
	JsonKey.lib: _fileUriPath(package.packageUriRoot),
	},
	},
	if (languageVersionOverride case var override?)
	JsonKey.languageVersionOverride: override.toString(),
	};
	}

	/// Package configuration information for a path in a readable format.
	@override
	String toString() {
	var buffer = StringBuffer();
	var sep = Platform.pathSeparator;
	var kind = path.endsWith(Platform.pathSeparator) ? 'directory' : 'file';
	buffer.writeln('Package configuration for $kind: ${p.relative(path)}');
	if (configPath case var configPath?) {
	buffer.writeln('- Package configuration: ${p.relative(configPath)}');
	if (package case var package?) {
	buffer.writeln('- In package: ${package.name}');
	if (package.languageVersion case var version?) {
	buffer.writeln(' - default language version: $version');
	}
	var rootUri = _fileUriPath(package.root);
	var rootPath = p.relative(Directory.fromUri(Uri.parse(rootUri)).path);
	buffer.writeln(' - with root: $rootPath$sep');
	if (packageUri case var packageUri?) {
	buffer.writeln(' - Has package URI: $packageUri');
	if (package.root != package.packageUriRoot) {
	var libPath = p.relative(
	Directory.fromUri(package.packageUriRoot).path,
	);
	buffer.writeln(' - relative to: $libPath$sep');
	} else {
	buffer.writeln(' - relative to root');
	}
	}
	} else {
	buffer.writeln('- Is not part of any package');
	}
	} else {
	buffer.writeln('- No package configuration found');
	assert(package == null);
	}
	if (languageVersionOverride case var override?) {
	buffer.writeln('- Language version override: // @dart=$override');
	}
	return buffer.toString();
	}

	static String _fileUriPath(Uri uri) {
	assert(uri.isScheme('file'));
	return File.fromUri(uri).path;
	}
	}

	// Constants for all used JSON keys to prevent mis-typing.
	extension type const JsonKey(String value) implements String {
	static const JsonKey path = JsonKey('path');
	static const JsonKey configPath = JsonKey('configPath');
	static const JsonKey package = JsonKey('package');
	static const JsonKey name = JsonKey('name');
	static const JsonKey root = JsonKey('root');
	static const JsonKey packageUri = JsonKey('packageUri');
	static const JsonKey lib = JsonKey('lib');
	static const JsonKey languageVersion = JsonKey('languageVersion');
	static const JsonKey languageVersionOverride = JsonKey(
	'languageVersionOverride',
	);
	}

	// --------------------------------------------------------------------
	// Find language version override marker in file.

	/// Tries to find a language override marker in a Dart file.
	///
	/// Uses a best-effort approach to scan for a line
	/// of the form `// @dart=X.Y` before any Dart directive.
	/// Any consistently and idiomatically formatted file will be recognized
	/// correctly. A file with a multiline `/.../` comment where
	/// internal lines do not start with `*`, or where a Dart directive
	/// follows a `*/` on the same line, may be misinterpreted.
	LanguageVersion? _readOverrideVersion(File file) {
	String fileContent;
	try {
	fileContent = file.readAsStringSync();
	} catch (e) {
	stderr
	..writeln('Error reading ${file.path} as UTF-8 text:')
	..writeln(e);
	return null;
	}
	// Skip BOM only at start.
	const bom = '\uFEFF';
	var contentStart = 0;
	// Skip BOM only at start.
	if (fileContent.startsWith(bom)) contentStart = 1;
	// Skip `#! ...` line only at start.
	if (fileContent.startsWith('#!', contentStart)) {
	// Skip until end-of-line, whether ended by `\n` or `\r\n`.
	var endOfHashBang = fileContent.indexOf('\n', contentStart + 2);
	if (endOfHashBang < 0) return null; // No EOL after `#!`.
	contentStart = endOfHashBang + 1;
	}
	// Match lines until one that looks like a version override or not a comment.
	for (var match in leadRegExp.allMatches(fileContent, contentStart)) {
	if (match.namedGroup('major') case var major?) {
	// Found `// @dart=<major>.<minor>` line.
	var minor = match.namedGroup('minor')!;
	return LanguageVersion(int.parse(major), int.parse(minor));
	} else if (match.namedGroup('other') != null) {
	// Found non-comment, so too late for language version markers.
	break;
	}
	}
	return null;
	}

	/// Heuristic scanner for finding leading comment lines.
	///
	/// Finds leading comments and any language version override marker
	/// within them.
	///
	/// Accepts empty lines or lines starting with `/`, `` or `//` as
	/// initial comment lines, and any other non-space/tab first character
	/// as a non-comment, which ends the section
	/// that can contain language overrides.
	///
	/// It's possible to construct files where that's not correct, fx.
	/// ```
	/// /* something */ import "banana.dart";
	/// // @dart=2.14
	/// ```
	/// To be absolutely certain, the code would need to properly tokenize
	/// nested comments, which is not a job for a RegExp.
	/// This RegExp should work for well-behaved and -formatted files.
	final leadRegExp = RegExp(
	r'^[ \t]*'
	r'(?:'
	r'$' // Empty line
	r'\|'
	r'/?\' // Line starting with `/` or `*`, assumed a comment continuation.
	r'\|'
	// Line starting with `//`, and possibly followed by language override.
	r'//(?: @ dart = (?<major>\d+) \. (?<minor>\d+) *$)?'
	r'\|'
	r'(?<other>[^ \t/*])' // Any other line, assumed to end initial comments.
	r')',
	multiLine: true,
	);

	// --------------------------------------------------------------------
	// Find and load (and cache) package configurations

	class PackageConfigLoader {
	/// Stop searching at the current working directory.
	final bool noParent;

	/// Stop searching if finding a `pubspec.yaml` with no package configuration.
	final bool stopAtPubspec;

	/// Cache lookup results in case someone does more lookups on the same path.
	final Map<
	(String path, bool stopAtPubspec),
	(String? configPath, PackageConfig? config)
	>
	_packageConfigCache = {};

	PackageConfigLoader({this.stopAtPubspec = false, this.noParent = false});

	/// Finds a package configuration relative to [path].
	///
	/// Caches result for each directory looked at.
	/// If someone does multiple lookups in the same directory, there is no need
	/// to find and parse the same configuration more than once.
	Future<(String? path, PackageConfig? config)> findPackageConfig(
	String path,
	) async =>
	_packageConfigCache[(
	path,
	stopAtPubspec,
	)] ??= await _findPackageConfigNoCache(path);

	Future<(String? path, PackageConfig? config)> _findPackageConfigNoCache(
	String path,
	) async {
	var configPath = p.join(path, '.dart_tool', 'package_config.json');
	var configFile = File(configPath);
	if (configFile.existsSync()) {
	var hasError = false;
	var config = await loadPackageConfig(
	configFile.absolute,
	onError: (error) {
	stderr.writeln(
	'Error parsing package configuration config ($configPath):\n'
	' $error',
	);
	hasError = true;
	},
	);
	return (configPath, hasError ? null : config);
	}
	if (stopAtPubspec) {
	var pubspecPath = p.join(path, 'pubspec.yaml');
	var pubspecFile = File(pubspecPath);
	if (pubspecFile.existsSync()) {
	stderr
	..writeln('Found pubspec.yaml with no .dart_tool/package_config.json')
	..writeln(' at $path');
	return (null, null);
	}
	}
	if (noParent && path == p.current) return (null, null);
	var parentPath = p.dirname(path);
	if (parentPath == path) return (null, null);
	// Recurse on parent path.
	return findPackageConfig(parentPath);
	}
	}

	const String usage = '''
	Usage: dart package_config_of.dart [-p\|-j\|-jl\|-h] PATH*

	Searches from (each) PATH for a `.dart_tool/package_config.json` file,
	loads that, and prints information about that package configuration
	and the configuration for PATH in it.
	If no PATH is given, the current directory is used.

	Flags:
	-p : Stop when finding a 'pubspec.yaml' file without a package config.
	The default is to ignore `pubspec.yaml` files and only look for
	`.dart_tool/package_config.json` files, which will work correctly
	for Pub workspaces.
	-b : Stop if reaching the current working directory.
	When looking for a package configuration, don't try further out
	than the current directory.
	Only works for starting PATHs inside the current directory.
	-j : Output as JSON. Emits a single JSON object for each file, on
	a line of its own (JSON-lines format). See format below.
	Default is to output human readable text.
	-jl : Emits as a single JSON list containing the JSON outputs.
	See format of individual elements below.
	Default is to output human readable text.
	-h : Print this help text. Ignore any PATHs.

	A JSON object written using -j or -jl has following entries:
	"path": "PATH", normalized and ends in a `/` if a directory.
	"configPath": path to config file. Omitted if no or invalid config.
	"package": The package that PATH belongs to, if any. A map with:
	"name": Package name.
	"root": Path to package root.
	"languageVersion": "A.B", default language version for package.
	"packageUri": The package: URI of PATH, if one exists.
	"lib": If package URI exists, the package URI root,
	unless it's the same as the package root.
	"languageVersionOverride": "A.B", if file has '//@dart=' version override.
	''';