packages/flutter_goldens_client/lib/skia_client.dart - mirrors/flutter - Git at Google

 // Copyright 2014 The Flutter Authors. 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:convert';
 import 'dart:io' as io;

 import 'package:crypto/crypto.dart';
 import 'package:file/file.dart';
 import 'package:file/local.dart';
 import 'package:path/path.dart' as path;
 import 'package:platform/platform.dart';
 import 'package:process/process.dart';

 // If you are here trying to figure out how to use golden files in the Flutter
 // repo itself, consider reading this wiki page:
 // https://github.com/flutter/flutter/wiki/Writing-a-golden-file-test-for-package%3Aflutter

 const String _kFlutterRootKey = 'FLUTTER_ROOT';
 const String _kGoldctlKey = 'GOLDCTL';
 const String _kTestBrowserKey = 'FLUTTER_TEST_BROWSER';
 const String _kWebRendererKey = 'FLUTTER_WEB_RENDERER';

 /// Exception thrown when an error is returned from the [SkiaClient].
 class SkiaException implements Exception {
   /// Creates a new `SkiaException` with a required error [message].
   const SkiaException(this.message);

   /// A message describing the error.
   final String message;

   /// Returns a description of the Skia exception.
   ///
   /// The description always contains the [message].
   @override
   String toString() => 'SkiaException: $message';
 }

 /// A client for uploading image tests and making baseline requests to the
 /// Flutter Gold Dashboard.
 class SkiaGoldClient {
   /// Creates a [SkiaGoldClient] with the given [workDirectory].
   ///
   /// All other parameters are optional. They may be provided in tests to
   /// override the defaults for [fs], [process], [platform], and [httpClient].
   SkiaGoldClient(
     this.workDirectory, {
     this.fs = const LocalFileSystem(),
     this.process = const LocalProcessManager(),
     this.platform = const LocalPlatform(),
     io.HttpClient? httpClient,
   }) : httpClient = httpClient ?? io.HttpClient();

   /// The file system to use for storing the local clone of the repository.
   ///
   /// This is useful in tests, where a local file system (the default) can be
   /// replaced by a memory file system.
   final FileSystem fs;

   /// A wrapper for the [dart:io.Platform] API.
   ///
   /// This is useful in tests, where the system platform (the default) can be
   /// replaced by a mock platform instance.
   final Platform platform;

   /// A controller for launching sub-processes.
   ///
   /// This is useful in tests, where the real process manager (the default) can
   /// be replaced by a mock process manager that doesn't really create
   /// sub-processes.
   final ProcessManager process;

   /// A client for making Http requests to the Flutter Gold dashboard.
   final io.HttpClient httpClient;

   /// The local [Directory] within the [comparisonRoot] for the current test
   /// context. In this directory, the client will create image and JSON files
   /// for the goldctl tool to use.
   ///
   /// This is informed by the [FlutterGoldenFileComparator] [basedir]. It cannot
   /// be null.
   final Directory workDirectory;

   /// The local [Directory] where the Flutter repository is hosted.
   ///
   /// Uses the [fs] file system.
   Directory get _flutterRoot => fs.directory(platform.environment[_kFlutterRootKey]);

   /// The path to the local [Directory] where the goldctl tool is hosted.
   ///
   /// Uses the [platform] environment in this implementation.
   String get _goldctl => platform.environment[_kGoldctlKey]!;

   /// Prepares the local work space for golden file testing and calls the
   /// goldctl `auth` command.
   ///
   /// This ensures that the goldctl tool is authorized and ready for testing.
   /// Used by the [FlutterPostSubmitFileComparator] and the
   /// [FlutterPreSubmitFileComparator].
   Future<void> auth() async {
     if (await clientIsAuthorized()) {
       return;
     }
     final List<String> authCommand = <String>[
       _goldctl,
       'auth',
       '--work-dir', workDirectory
         .childDirectory('temp')
         .path,
       '--luci',
     ];

     final io.ProcessResult result = await process.run(authCommand);

     if (result.exitCode != 0) {
       final StringBuffer buf = StringBuffer()
         ..writeln('Skia Gold authorization failed.')
         ..writeln('Luci environments authenticate using the file provided '
           'by LUCI_CONTEXT. There may be an error with this file or Gold '
           'authentication.')
         ..writeln('Debug information for Gold --------------------------------')
         ..writeln('stdout: ${result.stdout}')
         ..writeln('stderr: ${result.stderr}');
       throw SkiaException(buf.toString());
     }
   }

   /// Signals if this client is initialized for uploading images to the Gold
   /// service.
   ///
   /// Since Flutter framework tests are executed in parallel, and in random
   /// order, this will signal is this instance of the Gold client has been
   /// initialized.
   bool _initialized = false;

   /// Executes the `imgtest init` command in the goldctl tool.
   ///
   /// The `imgtest` command collects and uploads test results to the Skia Gold
   /// backend, the `init` argument initializes the current test. Used by the
   /// [FlutterPostSubmitFileComparator].
   Future<void> imgtestInit() async {
     // This client has already been initialized
     if (_initialized) {
       return;
     }

     final File keys = workDirectory.childFile('keys.json');
     final File failures = workDirectory.childFile('failures.json');

     await keys.writeAsString(_getKeysJSON());
     await failures.create();
     final String commitHash = await _getCurrentCommit();

     final List<String> imgtestInitCommand = <String>[
       _goldctl,
       'imgtest', 'init',
       '--instance', 'flutter',
       '--work-dir', workDirectory
         .childDirectory('temp')
         .path,
       '--commit', commitHash,
       '--keys-file', keys.path,
       '--failure-file', failures.path,
       '--passfail',
     ];

     if (imgtestInitCommand.contains(null)) {
       final StringBuffer buf = StringBuffer()
         ..writeln('A null argument was provided for Skia Gold imgtest init.')
         ..writeln('Please confirm the settings of your golden file test.')
         ..writeln('Arguments provided:');
       imgtestInitCommand.forEach(buf.writeln);
       throw SkiaException(buf.toString());
     }

     final io.ProcessResult result = await process.run(imgtestInitCommand);

     if (result.exitCode != 0) {
       _initialized = false;
       final StringBuffer buf = StringBuffer()
         ..writeln('Skia Gold imgtest init failed.')
         ..writeln('An error occurred when initializing golden file test with ')
         ..writeln('goldctl.')
         ..writeln()
         ..writeln('Debug information for Gold --------------------------------')
         ..writeln('stdout: ${result.stdout}')
         ..writeln('stderr: ${result.stderr}');
       throw SkiaException(buf.toString());
     }
     _initialized = true;
   }

   /// Executes the `imgtest add` command in the goldctl tool.
   ///
   /// The `imgtest` command collects and uploads test results to the Skia Gold
   /// backend, the `add` argument uploads the current image test. A response is
   /// returned from the invocation of this command that indicates a pass or fail
   /// result.
   ///
   /// The [testName] and [goldenFile] parameters reference the current
   /// comparison being evaluated by the [FlutterPostSubmitFileComparator].
   Future<bool> imgtestAdd(String testName, File goldenFile) async {
     final List<String> imgtestCommand = <String>[
       _goldctl,
       'imgtest', 'add',
       '--work-dir', workDirectory
         .childDirectory('temp')
         .path,
       '--test-name', cleanTestName(testName),
       '--png-file', goldenFile.path,
       '--passfail',
       ..._getPixelMatchingArguments(),
     ];

     final io.ProcessResult result = await process.run(imgtestCommand);

     if (result.exitCode != 0) {
       // If an unapproved image has made it to post-submit, throw to close the
       // tree.
       String? resultContents;
       final File resultFile = workDirectory.childFile(fs.path.join(
         'result-state.json',
       ));
       if (await resultFile.exists()) {
         resultContents = await resultFile.readAsString();
       }

       final StringBuffer buf = StringBuffer()
         ..writeln('Skia Gold received an unapproved image in post-submit ')
         ..writeln('testing. Golden file images in flutter/flutter are triaged ')
         ..writeln('in pre-submit during code review for the given PR.')
         ..writeln()
         ..writeln('Visit https://flutter-gold.skia.org/ to view and approve ')
         ..writeln('the image(s), or revert the associated change. For more ')
         ..writeln('information, visit the wiki: ')
         ..writeln('https://github.com/flutter/flutter/wiki/Writing-a-golden-file-test-for-package:flutter')
         ..writeln()
         ..writeln('Debug information for Gold --------------------------------')
         ..writeln('stdout: ${result.stdout}')
         ..writeln('stderr: ${result.stderr}')
         ..writeln()
         ..writeln('result-state.json: ${resultContents ?? 'No result file found.'}');
       throw SkiaException(buf.toString());
     }

     return true;
   }

   /// Signals if this client is initialized for uploading tryjobs to the Gold
   /// service.
   ///
   /// Since Flutter framework tests are executed in parallel, and in random
   /// order, this will signal is this instance of the Gold client has been
   /// initialized for tryjobs.
   bool _tryjobInitialized = false;

   /// Executes the `imgtest init` command in the goldctl tool for tryjobs.
   ///
   /// The `imgtest` command collects and uploads test results to the Skia Gold
   /// backend, the `init` argument initializes the current tryjob. Used by the
   /// [FlutterPreSubmitFileComparator].
   Future<void> tryjobInit() async {
     // This client has already been initialized
     if (_tryjobInitialized) {
       return;
     }

     final File keys = workDirectory.childFile('keys.json');
     final File failures = workDirectory.childFile('failures.json');

     await keys.writeAsString(_getKeysJSON());
     await failures.create();
     final String commitHash = await _getCurrentCommit();

     final List<String> imgtestInitCommand = <String>[
       _goldctl,
       'imgtest', 'init',
       '--instance', 'flutter',
       '--work-dir', workDirectory
         .childDirectory('temp')
         .path,
       '--commit', commitHash,
       '--keys-file', keys.path,
       '--failure-file', failures.path,
       '--passfail',
       '--crs', 'github',
       '--patchset_id', commitHash,
       ...getCIArguments(),
     ];

     if (imgtestInitCommand.contains(null)) {
       final StringBuffer buf = StringBuffer()
         ..writeln('A null argument was provided for Skia Gold tryjob init.')
         ..writeln('Please confirm the settings of your golden file test.')
         ..writeln('Arguments provided:');
       imgtestInitCommand.forEach(buf.writeln);
       throw SkiaException(buf.toString());
     }

     final io.ProcessResult result = await process.run(imgtestInitCommand);

     if (result.exitCode != 0) {
       _tryjobInitialized = false;
       final StringBuffer buf = StringBuffer()
         ..writeln('Skia Gold tryjobInit failure.')
         ..writeln('An error occurred when initializing golden file tryjob with ')
         ..writeln('goldctl.')
         ..writeln()
         ..writeln('Debug information for Gold --------------------------------')
         ..writeln('stdout: ${result.stdout}')
         ..writeln('stderr: ${result.stderr}');
       throw SkiaException(buf.toString());
     }
     _tryjobInitialized = true;
   }

   /// Executes the `imgtest add` command in the goldctl tool for tryjobs.
   ///
   /// The `imgtest` command collects and uploads test results to the Skia Gold
   /// backend, the `add` argument uploads the current image test. A response is
   /// returned from the invocation of this command that indicates a pass or fail
   /// result for the tryjob.
   ///
   /// The [testName] and [goldenFile] parameters reference the current
   /// comparison being evaluated by the [FlutterPreSubmitFileComparator].
   Future<void> tryjobAdd(String testName, File goldenFile) async {
     final List<String> imgtestCommand = <String>[
       _goldctl,
       'imgtest', 'add',
       '--work-dir', workDirectory
         .childDirectory('temp')
         .path,
       '--test-name', cleanTestName(testName),
       '--png-file', goldenFile.path,
       ..._getPixelMatchingArguments(),
     ];

     final io.ProcessResult result = await process.run(imgtestCommand);

     final String/*!*/ resultStdout = result.stdout.toString();
     if (result.exitCode != 0 &&
       !(resultStdout.contains('Untriaged') || resultStdout.contains('negative image'))) {
       String? resultContents;
       final File resultFile = workDirectory.childFile(fs.path.join(
         'result-state.json',
       ));
       if (await resultFile.exists()) {
         resultContents = await resultFile.readAsString();
       }
       final StringBuffer buf = StringBuffer()
         ..writeln('Unexpected Gold tryjobAdd failure.')
         ..writeln('Tryjob execution for golden file test $testName failed for')
         ..writeln('a reason unrelated to pixel comparison.')
         ..writeln()
         ..writeln('Debug information for Gold --------------------------------')
         ..writeln('stdout: ${result.stdout}')
         ..writeln('stderr: ${result.stderr}')
         ..writeln()
         ..writeln()
         ..writeln('result-state.json: ${resultContents ?? 'No result file found.'}');
       throw SkiaException(buf.toString());
     }
   }

   // Constructs arguments for `goldctl` for controlling how pixels are compared.
   //
   // For AOT and CanvasKit exact pixel matching is used. For the HTML renderer
   // on the web a fuzzy matching algorithm is used that allows very small deltas
   // because Chromium cannot exactly reproduce the same golden on all computers.
   // It seems to depend on the hardware/OS/driver combination. However, those
   // differences are very small (typically not noticeable to human eye).
   List<String> _getPixelMatchingArguments() {
     // Only use fuzzy pixel matching in the HTML renderer.
     if (!_isBrowserTest || _isBrowserCanvasKitTest) {
       return const <String>[];
     }

     // The algorithm to be used when matching images. The available options are:
     // - "fuzzy": Allows for customizing the thresholds of pixel differences.
     // - "sobel": Same as "fuzzy" but performs edge detection before performing
     //            a fuzzy match.
     const String algorithm = 'fuzzy';

     // The number of pixels in this image that are allowed to differ from the
     // baseline.
     //
     // The chosen number - 20 - is arbitrary. Even for a small golden file, say
     // 50 x 50, it would be less than 1% of the total number of pixels. This
     // number should not grow too much. If it's growing, it is probably due to a
     // larger issue that needs to be addressed at the infra level.
     const int maxDifferentPixels = 20;

     // The maximum acceptable difference per pixel.
     //
     // Uses the Manhattan distance using the RGBA color components as
     // coordinates. The chosen number - 4 - is arbitrary. It's small enough to
     // both not be noticeable and not trigger test flakes due to sub-pixel
     // golden deltas. This number should not grow too much. If it's growing, it
     // is probably due to a larger issue that needs to be addressed at the infra
     // level.
     const int pixelDeltaThreshold = 4;

     return <String>[
       '--add-test-optional-key', 'image_matching_algorithm:$algorithm',
       '--add-test-optional-key', 'fuzzy_max_different_pixels:$maxDifferentPixels',
       '--add-test-optional-key', 'fuzzy_pixel_delta_threshold:$pixelDeltaThreshold',
     ];
   }

   /// Returns the latest positive digest for the given test known to Flutter
   /// Gold at head.
   Future<String?> getExpectationForTest(String testName) async {
     late String? expectation;
     final String traceID = getTraceID(testName);
     await io.HttpOverrides.runWithHttpOverrides<Future<void>>(() async {
       final Uri requestForExpectations = Uri.parse(
         'https://flutter-gold.skia.org/json/v2/latestpositivedigest/$traceID'
       );
       late String rawResponse;
       try {
         final io.HttpClientRequest request = await httpClient.getUrl(requestForExpectations);
         final io.HttpClientResponse response = await request.close();
         rawResponse = await utf8.decodeStream(response);
         final dynamic jsonResponse = json.decode(rawResponse);
         if (jsonResponse is! Map<String, dynamic>) {
           throw const FormatException('Skia gold expectations do not match expected format.');
         }
         expectation = jsonResponse['digest'] as String?;
       } on FormatException catch (error) {
         // Ideally we'd use something like package:test's printOnError, but best reliability
         // in getting logs on CI for now we're just using print.
         // See also: https://github.com/flutter/flutter/issues/91285
         print( // ignore: avoid_print
           'Formatting error detected requesting expectations from Flutter Gold.\n'
           'error: $error\n'
           'url: $requestForExpectations\n'
           'response: $rawResponse'
         );
         rethrow;
       }
     },
       SkiaGoldHttpOverrides(),
     );
     return expectation;
   }

   /// Returns a list of bytes representing the golden image retrieved from the
   /// Flutter Gold dashboard.
   ///
   /// The provided image hash represents an expectation from Flutter Gold.
   Future<List<int>>getImageBytes(String imageHash) async {
     final List<int> imageBytes = <int>[];
     await io.HttpOverrides.runWithHttpOverrides<Future<void>>(() async {
       final Uri requestForImage = Uri.parse(
         'https://flutter-gold.skia.org/img/images/$imageHash.png',
       );
       final io.HttpClientRequest request = await httpClient.getUrl(requestForImage);
       final io.HttpClientResponse response = await request.close();
       await response.forEach((List<int> bytes) => imageBytes.addAll(bytes));
     },
       SkiaGoldHttpOverrides(),
     );
     return imageBytes;
   }

   /// Returns the current commit hash of the Flutter repository.
   Future<String> _getCurrentCommit() async {
     if (!_flutterRoot.existsSync()) {
       throw SkiaException('Flutter root could not be found: $_flutterRoot\n');
     } else {
       final io.ProcessResult revParse = await process.run(
         <String>['git', 'rev-parse', 'HEAD'],
         workingDirectory: _flutterRoot.path,
       );
       if (revParse.exitCode != 0) {
         throw const SkiaException('Current commit of Flutter can not be found.');
       }
       return (revParse.stdout as String/*!*/).trim();
     }
   }

   /// Returns a JSON String with keys value pairs used to uniquely identify the
   /// configuration that generated the given golden file.
   ///
   /// Currently, the only key value pairs being tracked is the platform the
   /// image was rendered on, and for web tests, the browser the image was
   /// rendered on.
   String _getKeysJSON() {
     final Map<String, dynamic> keys = <String, dynamic>{
       'Platform' : platform.operatingSystem,
       'CI' : 'luci',
     };
     if (_isBrowserTest) {
       keys['Browser'] = _browserKey;
       keys['Platform'] = '${keys['Platform']}-browser';
       if (_isBrowserCanvasKitTest) {
         keys['WebRenderer'] = 'canvaskit';
       }
     }
     return json.encode(keys);
   }

   /// Removes the file extension from the [fileName] to represent the test name
   /// properly.
   String cleanTestName(String fileName) {
     return fileName.split(path.extension(fileName))[0];
   }

   /// Returns a boolean value to prevent the client from re-authorizing itself
   /// for multiple tests.
   Future<bool> clientIsAuthorized() async {
     final File authFile = workDirectory.childFile(fs.path.join(
       'temp',
       'auth_opt.json',
     ))/*!*/;

     if (await authFile.exists()) {
       final String contents = await authFile.readAsString();
       final Map<String, dynamic> decoded = json.decode(contents) as Map<String, dynamic>;
       return !(decoded['GSUtil'] as bool/*!*/);
     }
     return false;
   }

   /// Returns a list of arguments for initializing a tryjob based on the testing
   /// environment.
   List<String> getCIArguments() {
     final String jobId = platform.environment['LOGDOG_STREAM_PREFIX']!.split('/').last;
     final List<String> refs = platform.environment['GOLD_TRYJOB']!.split('/');
     final String pullRequest = refs[refs.length - 2];

     return <String>[
       '--changelist', pullRequest,
       '--cis', 'buildbucket',
       '--jobid', jobId,
     ];
   }

   bool get _isBrowserTest {
     return platform.environment[_kTestBrowserKey] != null;
   }

   bool get _isBrowserCanvasKitTest {
     return _isBrowserTest && platform.environment[_kWebRendererKey] == 'canvaskit';
   }

   String get _browserKey {
     assert(_isBrowserTest);
     return platform.environment[_kTestBrowserKey]!;
   }

   /// Returns a trace id based on the current testing environment to lookup
   /// the latest positive digest on Flutter Gold with a hex-encoded md5 hash of
   /// the image keys.
   String getTraceID(String testName) {
     final Map<String, dynamic> keys = <String, dynamic>{
       if (_isBrowserTest)
         'Browser' : _browserKey,
       if (_isBrowserCanvasKitTest)
         'WebRenderer' : 'canvaskit',
       'CI' : 'luci',
       'Platform' : platform.operatingSystem,
       'name' : testName,
       'source_type' : 'flutter',
     };
     final String jsonTrace = json.encode(keys);
     final String md5Sum = md5.convert(utf8.encode(jsonTrace)).toString();
     return md5Sum;
   }
 }

 /// Used to make HttpRequests during testing.
 class SkiaGoldHttpOverrides extends io.HttpOverrides { }
	// Copyright 2014 The Flutter Authors. 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:convert';
	import 'dart:io' as io;

	import 'package:crypto/crypto.dart';
	import 'package:file/file.dart';
	import 'package:file/local.dart';
	import 'package:path/path.dart' as path;
	import 'package:platform/platform.dart';
	import 'package:process/process.dart';

	// If you are here trying to figure out how to use golden files in the Flutter
	// repo itself, consider reading this wiki page:
	// https://github.com/flutter/flutter/wiki/Writing-a-golden-file-test-for-package%3Aflutter

	const String _kFlutterRootKey = 'FLUTTER_ROOT';
	const String _kGoldctlKey = 'GOLDCTL';
	const String _kTestBrowserKey = 'FLUTTER_TEST_BROWSER';
	const String _kWebRendererKey = 'FLUTTER_WEB_RENDERER';

	/// Exception thrown when an error is returned from the [SkiaClient].
	class SkiaException implements Exception {
	/// Creates a new `SkiaException` with a required error [message].
	const SkiaException(this.message);

	/// A message describing the error.
	final String message;

	/// Returns a description of the Skia exception.
	///
	/// The description always contains the [message].
	@override
	String toString() => 'SkiaException: $message';
	}

	/// A client for uploading image tests and making baseline requests to the
	/// Flutter Gold Dashboard.
	class SkiaGoldClient {
	/// Creates a [SkiaGoldClient] with the given [workDirectory].
	///
	/// All other parameters are optional. They may be provided in tests to
	/// override the defaults for [fs], [process], [platform], and [httpClient].
	SkiaGoldClient(
	this.workDirectory, {
	this.fs = const LocalFileSystem(),
	this.process = const LocalProcessManager(),
	this.platform = const LocalPlatform(),
	io.HttpClient? httpClient,
	}) : httpClient = httpClient ?? io.HttpClient();

	/// The file system to use for storing the local clone of the repository.
	///
	/// This is useful in tests, where a local file system (the default) can be
	/// replaced by a memory file system.
	final FileSystem fs;

	/// A wrapper for the [dart:io.Platform] API.
	///
	/// This is useful in tests, where the system platform (the default) can be
	/// replaced by a mock platform instance.
	final Platform platform;

	/// A controller for launching sub-processes.
	///
	/// This is useful in tests, where the real process manager (the default) can
	/// be replaced by a mock process manager that doesn't really create
	/// sub-processes.
	final ProcessManager process;

	/// A client for making Http requests to the Flutter Gold dashboard.
	final io.HttpClient httpClient;

	/// The local [Directory] within the [comparisonRoot] for the current test
	/// context. In this directory, the client will create image and JSON files
	/// for the goldctl tool to use.
	///
	/// This is informed by the [FlutterGoldenFileComparator] [basedir]. It cannot
	/// be null.
	final Directory workDirectory;

	/// The local [Directory] where the Flutter repository is hosted.
	///
	/// Uses the [fs] file system.
	Directory get _flutterRoot => fs.directory(platform.environment[_kFlutterRootKey]);

	/// The path to the local [Directory] where the goldctl tool is hosted.
	///
	/// Uses the [platform] environment in this implementation.
	String get _goldctl => platform.environment[_kGoldctlKey]!;

	/// Prepares the local work space for golden file testing and calls the
	/// goldctl `auth` command.
	///
	/// This ensures that the goldctl tool is authorized and ready for testing.
	/// Used by the [FlutterPostSubmitFileComparator] and the
	/// [FlutterPreSubmitFileComparator].
	Future<void> auth() async {
	if (await clientIsAuthorized()) {
	return;
	}
	final List<String> authCommand = <String>[
	_goldctl,
	'auth',
	'--work-dir', workDirectory
	.childDirectory('temp')
	.path,
	'--luci',
	];

	final io.ProcessResult result = await process.run(authCommand);

	if (result.exitCode != 0) {
	final StringBuffer buf = StringBuffer()
	..writeln('Skia Gold authorization failed.')
	..writeln('Luci environments authenticate using the file provided '
	'by LUCI_CONTEXT. There may be an error with this file or Gold '
	'authentication.')
	..writeln('Debug information for Gold --------------------------------')
	..writeln('stdout: ${result.stdout}')
	..writeln('stderr: ${result.stderr}');
	throw SkiaException(buf.toString());
	}
	}

	/// Signals if this client is initialized for uploading images to the Gold
	/// service.
	///
	/// Since Flutter framework tests are executed in parallel, and in random
	/// order, this will signal is this instance of the Gold client has been
	/// initialized.
	bool _initialized = false;

	/// Executes the `imgtest init` command in the goldctl tool.
	///
	/// The `imgtest` command collects and uploads test results to the Skia Gold
	/// backend, the `init` argument initializes the current test. Used by the
	/// [FlutterPostSubmitFileComparator].
	Future<void> imgtestInit() async {
	// This client has already been initialized
	if (_initialized) {
	return;
	}

	final File keys = workDirectory.childFile('keys.json');
	final File failures = workDirectory.childFile('failures.json');

	await keys.writeAsString(_getKeysJSON());
	await failures.create();
	final String commitHash = await _getCurrentCommit();

	final List<String> imgtestInitCommand = <String>[
	_goldctl,
	'imgtest', 'init',
	'--instance', 'flutter',
	'--work-dir', workDirectory
	.childDirectory('temp')
	.path,
	'--commit', commitHash,
	'--keys-file', keys.path,
	'--failure-file', failures.path,
	'--passfail',
	];

	if (imgtestInitCommand.contains(null)) {
	final StringBuffer buf = StringBuffer()
	..writeln('A null argument was provided for Skia Gold imgtest init.')
	..writeln('Please confirm the settings of your golden file test.')
	..writeln('Arguments provided:');
	imgtestInitCommand.forEach(buf.writeln);
	throw SkiaException(buf.toString());
	}

	final io.ProcessResult result = await process.run(imgtestInitCommand);

	if (result.exitCode != 0) {
	_initialized = false;
	final StringBuffer buf = StringBuffer()
	..writeln('Skia Gold imgtest init failed.')
	..writeln('An error occurred when initializing golden file test with ')
	..writeln('goldctl.')
	..writeln()
	..writeln('Debug information for Gold --------------------------------')
	..writeln('stdout: ${result.stdout}')
	..writeln('stderr: ${result.stderr}');
	throw SkiaException(buf.toString());
	}
	_initialized = true;
	}

	/// Executes the `imgtest add` command in the goldctl tool.
	///
	/// The `imgtest` command collects and uploads test results to the Skia Gold
	/// backend, the `add` argument uploads the current image test. A response is
	/// returned from the invocation of this command that indicates a pass or fail
	/// result.
	///
	/// The [testName] and [goldenFile] parameters reference the current
	/// comparison being evaluated by the [FlutterPostSubmitFileComparator].
	Future<bool> imgtestAdd(String testName, File goldenFile) async {
	final List<String> imgtestCommand = <String>[
	_goldctl,
	'imgtest', 'add',
	'--work-dir', workDirectory
	.childDirectory('temp')
	.path,
	'--test-name', cleanTestName(testName),
	'--png-file', goldenFile.path,
	'--passfail',
	..._getPixelMatchingArguments(),
	];

	final io.ProcessResult result = await process.run(imgtestCommand);

	if (result.exitCode != 0) {
	// If an unapproved image has made it to post-submit, throw to close the
	// tree.
	String? resultContents;
	final File resultFile = workDirectory.childFile(fs.path.join(
	'result-state.json',
	));
	if (await resultFile.exists()) {
	resultContents = await resultFile.readAsString();
	}

	final StringBuffer buf = StringBuffer()
	..writeln('Skia Gold received an unapproved image in post-submit ')
	..writeln('testing. Golden file images in flutter/flutter are triaged ')
	..writeln('in pre-submit during code review for the given PR.')
	..writeln()
	..writeln('Visit https://flutter-gold.skia.org/ to view and approve ')
	..writeln('the image(s), or revert the associated change. For more ')
	..writeln('information, visit the wiki: ')
	..writeln('https://github.com/flutter/flutter/wiki/Writing-a-golden-file-test-for-package:flutter')
	..writeln()
	..writeln('Debug information for Gold --------------------------------')
	..writeln('stdout: ${result.stdout}')
	..writeln('stderr: ${result.stderr}')
	..writeln()
	..writeln('result-state.json: ${resultContents ?? 'No result file found.'}');
	throw SkiaException(buf.toString());
	}

	return true;
	}

	/// Signals if this client is initialized for uploading tryjobs to the Gold
	/// service.
	///
	/// Since Flutter framework tests are executed in parallel, and in random
	/// order, this will signal is this instance of the Gold client has been
	/// initialized for tryjobs.
	bool _tryjobInitialized = false;

	/// Executes the `imgtest init` command in the goldctl tool for tryjobs.
	///
	/// The `imgtest` command collects and uploads test results to the Skia Gold
	/// backend, the `init` argument initializes the current tryjob. Used by the
	/// [FlutterPreSubmitFileComparator].
	Future<void> tryjobInit() async {
	// This client has already been initialized
	if (_tryjobInitialized) {
	return;
	}

	final File keys = workDirectory.childFile('keys.json');
	final File failures = workDirectory.childFile('failures.json');

	await keys.writeAsString(_getKeysJSON());
	await failures.create();
	final String commitHash = await _getCurrentCommit();

	final List<String> imgtestInitCommand = <String>[
	_goldctl,
	'imgtest', 'init',
	'--instance', 'flutter',
	'--work-dir', workDirectory
	.childDirectory('temp')
	.path,
	'--commit', commitHash,
	'--keys-file', keys.path,
	'--failure-file', failures.path,
	'--passfail',
	'--crs', 'github',
	'--patchset_id', commitHash,
	...getCIArguments(),
	];

	if (imgtestInitCommand.contains(null)) {
	final StringBuffer buf = StringBuffer()
	..writeln('A null argument was provided for Skia Gold tryjob init.')
	..writeln('Please confirm the settings of your golden file test.')
	..writeln('Arguments provided:');
	imgtestInitCommand.forEach(buf.writeln);
	throw SkiaException(buf.toString());
	}

	final io.ProcessResult result = await process.run(imgtestInitCommand);

	if (result.exitCode != 0) {
	_tryjobInitialized = false;
	final StringBuffer buf = StringBuffer()
	..writeln('Skia Gold tryjobInit failure.')
	..writeln('An error occurred when initializing golden file tryjob with ')
	..writeln('goldctl.')
	..writeln()
	..writeln('Debug information for Gold --------------------------------')
	..writeln('stdout: ${result.stdout}')
	..writeln('stderr: ${result.stderr}');
	throw SkiaException(buf.toString());
	}
	_tryjobInitialized = true;
	}

	/// Executes the `imgtest add` command in the goldctl tool for tryjobs.
	///
	/// The `imgtest` command collects and uploads test results to the Skia Gold
	/// backend, the `add` argument uploads the current image test. A response is
	/// returned from the invocation of this command that indicates a pass or fail
	/// result for the tryjob.
	///
	/// The [testName] and [goldenFile] parameters reference the current
	/// comparison being evaluated by the [FlutterPreSubmitFileComparator].
	Future<void> tryjobAdd(String testName, File goldenFile) async {
	final List<String> imgtestCommand = <String>[
	_goldctl,
	'imgtest', 'add',
	'--work-dir', workDirectory
	.childDirectory('temp')
	.path,
	'--test-name', cleanTestName(testName),
	'--png-file', goldenFile.path,
	..._getPixelMatchingArguments(),
	];

	final io.ProcessResult result = await process.run(imgtestCommand);

	final String/!/ resultStdout = result.stdout.toString();
	if (result.exitCode != 0 &&
	!(resultStdout.contains('Untriaged') \|\| resultStdout.contains('negative image'))) {
	String? resultContents;
	final File resultFile = workDirectory.childFile(fs.path.join(
	'result-state.json',
	));
	if (await resultFile.exists()) {
	resultContents = await resultFile.readAsString();
	}
	final StringBuffer buf = StringBuffer()
	..writeln('Unexpected Gold tryjobAdd failure.')
	..writeln('Tryjob execution for golden file test $testName failed for')
	..writeln('a reason unrelated to pixel comparison.')
	..writeln()
	..writeln('Debug information for Gold --------------------------------')
	..writeln('stdout: ${result.stdout}')
	..writeln('stderr: ${result.stderr}')
	..writeln()
	..writeln()
	..writeln('result-state.json: ${resultContents ?? 'No result file found.'}');
	throw SkiaException(buf.toString());
	}
	}

	// Constructs arguments for `goldctl` for controlling how pixels are compared.
	//
	// For AOT and CanvasKit exact pixel matching is used. For the HTML renderer
	// on the web a fuzzy matching algorithm is used that allows very small deltas
	// because Chromium cannot exactly reproduce the same golden on all computers.
	// It seems to depend on the hardware/OS/driver combination. However, those
	// differences are very small (typically not noticeable to human eye).
	List<String> _getPixelMatchingArguments() {
	// Only use fuzzy pixel matching in the HTML renderer.
	if (!_isBrowserTest \|\| _isBrowserCanvasKitTest) {
	return const <String>[];
	}

	// The algorithm to be used when matching images. The available options are:
	// - "fuzzy": Allows for customizing the thresholds of pixel differences.
	// - "sobel": Same as "fuzzy" but performs edge detection before performing
	// a fuzzy match.
	const String algorithm = 'fuzzy';

	// The number of pixels in this image that are allowed to differ from the
	// baseline.
	//
	// The chosen number - 20 - is arbitrary. Even for a small golden file, say
	// 50 x 50, it would be less than 1% of the total number of pixels. This
	// number should not grow too much. If it's growing, it is probably due to a
	// larger issue that needs to be addressed at the infra level.
	const int maxDifferentPixels = 20;

	// The maximum acceptable difference per pixel.
	//
	// Uses the Manhattan distance using the RGBA color components as
	// coordinates. The chosen number - 4 - is arbitrary. It's small enough to
	// both not be noticeable and not trigger test flakes due to sub-pixel
	// golden deltas. This number should not grow too much. If it's growing, it
	// is probably due to a larger issue that needs to be addressed at the infra
	// level.
	const int pixelDeltaThreshold = 4;

	return <String>[
	'--add-test-optional-key', 'image_matching_algorithm:$algorithm',
	'--add-test-optional-key', 'fuzzy_max_different_pixels:$maxDifferentPixels',
	'--add-test-optional-key', 'fuzzy_pixel_delta_threshold:$pixelDeltaThreshold',
	];
	}

	/// Returns the latest positive digest for the given test known to Flutter
	/// Gold at head.
	Future<String?> getExpectationForTest(String testName) async {
	late String? expectation;
	final String traceID = getTraceID(testName);
	await io.HttpOverrides.runWithHttpOverrides<Future<void>>(() async {
	final Uri requestForExpectations = Uri.parse(
	'https://flutter-gold.skia.org/json/v2/latestpositivedigest/$traceID'
	);
	late String rawResponse;
	try {
	final io.HttpClientRequest request = await httpClient.getUrl(requestForExpectations);
	final io.HttpClientResponse response = await request.close();
	rawResponse = await utf8.decodeStream(response);
	final dynamic jsonResponse = json.decode(rawResponse);
	if (jsonResponse is! Map<String, dynamic>) {
	throw const FormatException('Skia gold expectations do not match expected format.');
	}
	expectation = jsonResponse['digest'] as String?;
	} on FormatException catch (error) {
	// Ideally we'd use something like package:test's printOnError, but best reliability
	// in getting logs on CI for now we're just using print.
	// See also: https://github.com/flutter/flutter/issues/91285
	print( // ignore: avoid_print
	'Formatting error detected requesting expectations from Flutter Gold.\n'
	'error: $error\n'
	'url: $requestForExpectations\n'
	'response: $rawResponse'
	);
	rethrow;
	}
	},
	SkiaGoldHttpOverrides(),
	);
	return expectation;
	}

	/// Returns a list of bytes representing the golden image retrieved from the
	/// Flutter Gold dashboard.
	///
	/// The provided image hash represents an expectation from Flutter Gold.
	Future<List<int>>getImageBytes(String imageHash) async {
	final List<int> imageBytes = <int>[];
	await io.HttpOverrides.runWithHttpOverrides<Future<void>>(() async {
	final Uri requestForImage = Uri.parse(
	'https://flutter-gold.skia.org/img/images/$imageHash.png',
	);
	final io.HttpClientRequest request = await httpClient.getUrl(requestForImage);
	final io.HttpClientResponse response = await request.close();
	await response.forEach((List<int> bytes) => imageBytes.addAll(bytes));
	},
	SkiaGoldHttpOverrides(),
	);
	return imageBytes;
	}

	/// Returns the current commit hash of the Flutter repository.
	Future<String> _getCurrentCommit() async {
	if (!_flutterRoot.existsSync()) {
	throw SkiaException('Flutter root could not be found: $_flutterRoot\n');
	} else {
	final io.ProcessResult revParse = await process.run(
	<String>['git', 'rev-parse', 'HEAD'],
	workingDirectory: _flutterRoot.path,
	);
	if (revParse.exitCode != 0) {
	throw const SkiaException('Current commit of Flutter can not be found.');
	}
	return (revParse.stdout as String/!/).trim();
	}
	}

	/// Returns a JSON String with keys value pairs used to uniquely identify the
	/// configuration that generated the given golden file.
	///
	/// Currently, the only key value pairs being tracked is the platform the
	/// image was rendered on, and for web tests, the browser the image was
	/// rendered on.
	String _getKeysJSON() {
	final Map<String, dynamic> keys = <String, dynamic>{
	'Platform' : platform.operatingSystem,
	'CI' : 'luci',
	};
	if (_isBrowserTest) {
	keys['Browser'] = _browserKey;
	keys['Platform'] = '${keys['Platform']}-browser';
	if (_isBrowserCanvasKitTest) {
	keys['WebRenderer'] = 'canvaskit';
	}
	}
	return json.encode(keys);
	}

	/// Removes the file extension from the [fileName] to represent the test name
	/// properly.
	String cleanTestName(String fileName) {
	return fileName.split(path.extension(fileName))[0];
	}

	/// Returns a boolean value to prevent the client from re-authorizing itself
	/// for multiple tests.
	Future<bool> clientIsAuthorized() async {
	final File authFile = workDirectory.childFile(fs.path.join(
	'temp',
	'auth_opt.json',
	))/!/;

	if (await authFile.exists()) {
	final String contents = await authFile.readAsString();
	final Map<String, dynamic> decoded = json.decode(contents) as Map<String, dynamic>;
	return !(decoded['GSUtil'] as bool/!/);
	}
	return false;
	}

	/// Returns a list of arguments for initializing a tryjob based on the testing
	/// environment.
	List<String> getCIArguments() {
	final String jobId = platform.environment['LOGDOG_STREAM_PREFIX']!.split('/').last;
	final List<String> refs = platform.environment['GOLD_TRYJOB']!.split('/');
	final String pullRequest = refs[refs.length - 2];

	return <String>[
	'--changelist', pullRequest,
	'--cis', 'buildbucket',
	'--jobid', jobId,
	];
	}

	bool get _isBrowserTest {
	return platform.environment[_kTestBrowserKey] != null;
	}

	bool get _isBrowserCanvasKitTest {
	return _isBrowserTest && platform.environment[_kWebRendererKey] == 'canvaskit';
	}

	String get _browserKey {
	assert(_isBrowserTest);
	return platform.environment[_kTestBrowserKey]!;
	}

	/// Returns a trace id based on the current testing environment to lookup
	/// the latest positive digest on Flutter Gold with a hex-encoded md5 hash of
	/// the image keys.
	String getTraceID(String testName) {
	final Map<String, dynamic> keys = <String, dynamic>{
	if (_isBrowserTest)
	'Browser' : _browserKey,
	if (_isBrowserCanvasKitTest)
	'WebRenderer' : 'canvaskit',
	'CI' : 'luci',
	'Platform' : platform.operatingSystem,
	'name' : testName,
	'source_type' : 'flutter',
	};
	final String jsonTrace = json.encode(keys);
	final String md5Sum = md5.convert(utf8.encode(jsonTrace)).toString();
	return md5Sum;
	}
	}

	/// Used to make HttpRequests during testing.
	class SkiaGoldHttpOverrides extends io.HttpOverrides { }