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Compare screenshots, generate report of differences. #8579

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Merged
merged 2 commits into from
Feb 25, 2025
Merged

Compare screenshots, generate report of differences. #8579

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b18ab58
Compare screenshots, generate report of differences.
isoos Feb 21, 2025
87ac3f7
Update pkg/pub_integration/tool/compare_screenshots.dart
isoos Feb 21, 2025
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1 change: 1 addition & 0 deletions pkg/pub_integration/pubspec.yaml
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Original file line number Diff line number Diff line change
Expand Up @@ -17,5 +17,6 @@ dependencies:

dev_dependencies:
coverage: any # test already depends on it
markdown: ^7.3.0
shelf: ^1.4.0
test: ^1.16.5
125 changes: 125 additions & 0 deletions pkg/pub_integration/tool/compare_screenshots.dart
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Original file line number Diff line number Diff line change
@@ -0,0 +1,125 @@
// 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.

import 'dart:io';

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

/// Compares the screenshots from the previous and current test runs.
/// Uses imagemagick for image processing.
///
/// `dart <script.dart> <before-dir> <after-dir> <report-dir>`
Future<void> main(List<String> args) async {
final beforeFiles = await _list(args[0]);
final afterFiles = await _list(args[1]);

final reportDir = Directory(args[2]);
await reportDir.create(recursive: true);
await _CompareTool(beforeFiles, afterFiles, reportDir)._compare();
}

class _CompareTool {
final Directory _reportDir;
final Map<String, File> _beforeFiles;
final Map<String, File> _afterFiles;
final _report = StringBuffer();

_CompareTool(
this._beforeFiles,
this._afterFiles,
this._reportDir,
);

Future<void> _compare() async {
_report.writeln(
'Screenshot comparison report generated at ${DateTime.now().toIso8601String()}.');

final newFiles = _afterFiles.keys
.where((key) => !_beforeFiles.containsKey(key))
.toList();
if (newFiles.isNotEmpty) {
_report.writeln([
'',
'# New files',
newFiles.map((e) => '- `$e`').join('\n'),
].join('\n\n'));
}

final missingFiles = _beforeFiles.keys
.where((key) => !_afterFiles.containsKey(key))
.toList();
if (missingFiles.isNotEmpty) {
_report.writeln([
'',
'# Missing files',
missingFiles.map((e) => '- `$e`').join('\n'),
].join('\n\n'));
}

for (final path in _afterFiles.keys) {
final after = _afterFiles[path]!;
if (!_beforeFiles.containsKey(path)) continue;
final before = _beforeFiles[path]!;

// quick byte-content check
final afterBytes = await after.readAsBytes();
final beforeBytes = await before.readAsBytes();
if (afterBytes.length == beforeBytes.length &&
afterBytes.indexed.every((e) => beforeBytes[e.$1] == e.$2)) {
continue;
}

final relativeDir = p.dirname(path);
final basename = p.basenameWithoutExtension(path);
final diffPath =
p.join(_reportDir.path, relativeDir, '$basename-diff.png');
await File(diffPath).parent.create(recursive: true);

final pr = await Process.run('compare', [
before.path,
after.path,
diffPath,
]);
if (pr.exitCode == 0) continue;

final beforeFile =
File(p.join(_reportDir.path, relativeDir, '$basename-before.png'));
await beforeFile.writeAsBytes(beforeBytes);
final afterFile =
File(p.join(_reportDir.path, relativeDir, '$basename-after.png'));
await afterFile.writeAsBytes(afterBytes);

_report.writeln('`$path`\n');
_report.writeln(
'![before](${p.join(relativeDir, '$basename-before.png')})\n');
_report
.writeln('![after](${p.join(relativeDir, '$basename-after.png')})\n');
_report
.writeln('![diff](${p.join(relativeDir, '$basename-diff.png')})\n');
_report.writeln();
}

await _writeIndexHtml();
}

Future<void> _writeIndexHtml() async {
await File(p.join(_reportDir.path, 'index.html')).writeAsString([
'<html><body>',
markdownToHtml(_report.toString()),
'</body></html>',
].join('\n'));
}
}

Future<Map<String, File>> _list(String path) async {
final map = <String, File>{};
await for (final file in Directory(path).list(recursive: true)) {
if (file is! File) continue;
final rp = p.relative(file.path, from: path);
map[rp] = file;
}
return Map.fromEntries(
map.entries.toList()..sort((a, b) => a.key.compareTo(b.key)));
}
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