[tool] Add initial file-based command skipping

script/tool/lib/src/analyze_command.dart

@@ -6,6 +6,7 @@ import 'dart:io' as io;
 
 import 'package:file/file.dart';
 
+import 'common/core.dart';
 import 'common/output_utils.dart';
 import 'common/package_looping_command.dart';
 import 'common/repository_package.dart';
@@ -92,6 +93,24 @@ class AnalyzeCommand extends PackageLoopingCommand {
     return false;
   }
 
+  @override
+  bool shouldIgnoreFile(String path) {
+    return repoLevelNonCodeImpactingFiles.contains(path) ||
+        // Native code, which is not part of Dart analysis.
+        path.endsWith('.c') ||
+        path.endsWith('.cc') ||
+        path.endsWith('.cpp') ||
+        path.endsWith('.h') ||
+        path.endsWith('.m') ||
+        path.endsWith('.swift') ||
+        path.endsWith('.java') ||
+        path.endsWith('.kt') ||
+        // Package metadata that doesn't impact analysis.
+        path.endsWith('/AUTHORS') ||
+        path.endsWith('/CHANGELOG.md') ||
+        path.endsWith('/README.md');
+  }
+
   @override
   Future<void> initializeRun() async {
     _allowedCustomAnalysisDirectories = getYamlListArg(_customAnalysisFlag);

script/tool/lib/src/build_examples_command.dart

@@ -134,6 +134,14 @@ class BuildExamplesCommand extends PackageLoopingCommand {
     return getNullableBoolArg(_swiftPackageManagerFlag);
   }
 
+  @override
+  bool shouldIgnoreFile(String path) {
+    return repoLevelNonCodeImpactingFiles.contains(path) ||
+        path.endsWith('/AUTHORS') ||
+        path.endsWith('/CHANGELOG.md') ||
+        path.endsWith('/README.md');
+  }
+
   @override
   Future<void> initializeRun() async {
     final List<String> platformFlags = _platforms.keys.toList();

script/tool/lib/src/common/core.dart

@@ -140,3 +140,24 @@ Directory? ciLogsDirectory(Platform platform, FileSystem fileSystem) {
   }
   return logsDirectory;
 }
+
+/// Full repo-relative paths to files that do not affect *any* code-related
+/// commands (example builds, Dart analysis, native code analysis, native tests,
+/// Dart tests, etc.) for use in command-ignored files lists for commands that
+/// are only affected by package code.
+const List<String> repoLevelNonCodeImpactingFiles = <String>[
+  'AUTHORS',
+  'CODEOWNERS',
+  'CONTRIBUTING.md',
+  'LICENSE',
+  'README.md',
+  // This deliberate lists specific files rather than excluding the whole
+  // .github directory since it's better to have false negatives than to
+  // accidentally skip tests if something is later added to the directory
+  // that could affect packages.
+  '.github/PULL_REQUEST_TEMPLATE.md',
+  '.github/dependabot.yml',
+  '.github/labeler.yml',
+  '.github/post_merge_labeler.yml',
+  '.github/workflows/pull_request_label.yml',
+];

script/tool/lib/src/common/package_looping_command.dart

@@ -109,6 +109,20 @@ abstract class PackageLoopingCommand extends PackageCommand {
   /// The package currently being run by [runForPackage].
   PackageEnumerationEntry? _currentPackageEntry;
 
+  /// When running against a merge base, this is called before [initializeRun]
+  /// for every changed file, to see if that file is a file that is guaranteed
+  /// *not* to require running this command.
+  ///
+  /// If every changed file returns true, then the command will be skipped.
+  /// Because this causes tests not to run, subclasses should be very
+  /// consevative about what returns true; for anything borderline it is much
+  /// better to err on the side of running tests unnecessarily than to risk
+  /// losing test coverage.
+  ///
+  /// [path] is a POSIX-style path regardless of the host platforrm, and is
+  /// relative to the git repo root.
+  bool shouldIgnoreFile(String path) => false;
+
   /// Called during [run] before any calls to [runForPackage]. This provides an
   /// opportunity to fail early if the command can't be run (e.g., because the
   /// arguments are invalid), and to set up any run-level state.
@@ -281,6 +295,14 @@ abstract class PackageLoopingCommand extends PackageCommand {
     baseSha = await gitVersionFinder.getBaseSha();
     changedFiles = await gitVersionFinder.getChangedFiles();
 
+    // Check whether the command needs to run.
+    if (changedFiles.isNotEmpty && changedFiles.every(shouldIgnoreFile)) {
+      _printColorized(
+          'SKIPPING ALL PACKAGES: No changed files affect this command',
+          Styles.DARK_GRAY);
+      return true;
+    }
+
     await initializeRun();
 
     final List<PackageEnumerationEntry> targetPackages =

script/tool/lib/src/dart_test_command.dart

@@ -65,6 +65,24 @@ class DartTestCommand extends PackageLoopingCommand {
   PackageLoopingType get packageLoopingType =>
       PackageLoopingType.includeAllSubpackages;
 
+  @override
+  bool shouldIgnoreFile(String path) {
+    return repoLevelNonCodeImpactingFiles.contains(path) ||
+        // Native code, which is not part of Dart unit testing.
+        path.endsWith('.c') ||
+        path.endsWith('.cc') ||
+        path.endsWith('.cpp') ||
+        path.endsWith('.h') ||
+        path.endsWith('.m') ||
+        path.endsWith('.swift') ||
+        path.endsWith('.java') ||
+        path.endsWith('.kt') ||
+        // Package metadata that doesn't impact Dart unit tests.
+        path.endsWith('/AUTHORS') ||
+        path.endsWith('/CHANGELOG.md') ||
+        path.endsWith('/README.md');
+  }
+
   @override
   Future<PackageResult> runForPackage(RepositoryPackage package) async {
     if (!package.testDirectory.existsSync()) {

script/tool/lib/src/drive_examples_command.dart

@@ -68,6 +68,14 @@ class DriveExamplesCommand extends PackageLoopingCommand {
 
   Map<String, List<String>> _targetDeviceFlags = const <String, List<String>>{};
 
+  @override
+  bool shouldIgnoreFile(String path) {
+    return repoLevelNonCodeImpactingFiles.contains(path) ||
+        path.endsWith('/AUTHORS') ||
+        path.endsWith('/CHANGELOG.md') ||
+        path.endsWith('/README.md');
+  }
+
   @override
   Future<void> initializeRun() async {
     final List<String> platformSwitches = <String>[

script/tool/lib/src/firebase_test_lab_command.dart

@@ -121,6 +121,14 @@ class FirebaseTestLabCommand extends PackageLoopingCommand {
     _firebaseProjectConfigured = true;
   }
 
+  @override
+  bool shouldIgnoreFile(String path) {
+    return repoLevelNonCodeImpactingFiles.contains(path) ||
+        path.endsWith('/AUTHORS') ||
+        path.endsWith('/CHANGELOG.md') ||
+        path.endsWith('/README.md');
+  }
+
   @override
   Future<PackageResult> runForPackage(RepositoryPackage package) async {
     final List<PackageResult> results = <PackageResult>[];

script/tool/lib/src/native_test_command.dart

@@ -113,6 +113,16 @@ this command.
 
   Set<String> _xcodeWarningsExceptions = <String>{};
 
+  @override
+  bool shouldIgnoreFile(String path) {
+    return repoLevelNonCodeImpactingFiles.contains(path) ||
+        path.endsWith('/AUTHORS') ||
+        path.endsWith('/CHANGELOG.md') ||
+        path.endsWith('/README.md');
+    // It may seem tempting to filter out *.dart, but that would skip critical
+    // testing since native integration tests run the full compiled application.
+  }
+
   @override
   Future<void> initializeRun() async {
     _platforms = <String, _PlatformDetails>{

script/tool/lib/src/xcode_analyze_command.dart

@@ -46,6 +46,14 @@ class XcodeAnalyzeCommand extends PackageLoopingCommand {
   final String description =
       'Runs Xcode analysis on the iOS and/or macOS example apps.';
 
+  @override
+  bool shouldIgnoreFile(String path) {
+    return repoLevelNonCodeImpactingFiles.contains(path) ||
+        path.endsWith('/AUTHORS') ||
+        path.endsWith('/CHANGELOG.md') ||
+        path.endsWith('/README.md');
+  }
+
   @override
   Future<void> initializeRun() async {
     if (!(getBoolArg(platformIOS) || getBoolArg(platformMacOS))) {

script/tool/test/analyze_command_test.dart

@@ -16,12 +16,13 @@ void main() {
   late MockPlatform mockPlatform;
   late Directory packagesDir;
   late RecordingProcessRunner processRunner;
+  late RecordingProcessRunner gitProcessRunner;
   late CommandRunner<void> runner;
 
   setUp(() {
     mockPlatform = MockPlatform();
     final GitDir gitDir;
-    (:packagesDir, :processRunner, gitProcessRunner: _, :gitDir) =
+    (:packagesDir, :processRunner, :gitProcessRunner, :gitDir) =
         configureBaseCommandMocks(platform: mockPlatform);
     final AnalyzeCommand analyzeCommand = AnalyzeCommand(
       packagesDir,
@@ -470,4 +471,90 @@ void main() {
       ]),
     );
   });
+
+  group('file filtering', () {
+    test('runs command for changes to Dart source', () async {
+      createFakePackage('package_a', packagesDir);
+
+      gitProcessRunner.mockProcessesForExecutable['git-diff'] =
+          <FakeProcessInfo>[
+        FakeProcessInfo(MockProcess(stdout: '''
+packages/package_a/foo.dart
+''')),
+      ];
+
+      final List<String> output =
+          await runCapturingPrint(runner, <String>['analyze']);
+
+      expect(
+          output,
+          containsAllInOrder(<Matcher>[
+            contains('Running for package_a'),
+          ]));
+    });
+
+    const List<String> files = <String>[
+      'foo.java',
+      'foo.kt',
+      'foo.m',
+      'foo.swift',
+      'foo.c',
+      'foo.cc',
+      'foo.cpp',
+      'foo.h',
+    ];
+    for (final String file in files) {
+      test('skips command for changes to non-Dart source $file', () async {
+        createFakePackage('package_a', packagesDir);
+
+        gitProcessRunner.mockProcessesForExecutable['git-diff'] =
+            <FakeProcessInfo>[
+          FakeProcessInfo(MockProcess(stdout: '''
+packages/package_a/$file
+''')),
+        ];
+
+        final List<String> output =
+            await runCapturingPrint(runner, <String>['analyze']);
+
+        expect(
+            output,
+            isNot(containsAllInOrder(<Matcher>[
+              contains('Running for package_a'),
+            ])));
+        expect(
+            output,
+            containsAllInOrder(<Matcher>[
+              contains('SKIPPING ALL PACKAGES'),
+            ]));
+      });
+    }
+
+    test('skips commands if all files should be ignored', () async {
+      createFakePackage('package_a', packagesDir);
+
+      gitProcessRunner.mockProcessesForExecutable['git-diff'] =
+          <FakeProcessInfo>[
+        FakeProcessInfo(MockProcess(stdout: '''
+README.md
+CODEOWNERS
+packages/package_a/CHANGELOG.md
+''')),
+      ];
+
+      final List<String> output =
+          await runCapturingPrint(runner, <String>['analyze']);
+
+      expect(
+          output,
+          isNot(containsAllInOrder(<Matcher>[
+            contains('Running for package_a'),
+          ])));
+      expect(
+          output,
+          containsAllInOrder(<Matcher>[
+            contains('SKIPPING ALL PACKAGES'),
+          ]));
+    });
+  });
 }

script/tool/test/build_examples_command_test.dart

@@ -19,11 +19,12 @@ void main() {
     late Directory packagesDir;
     late CommandRunner<void> runner;
     late RecordingProcessRunner processRunner;
+    late RecordingProcessRunner gitProcessRunner;
 
     setUp(() {
       mockPlatform = MockPlatform();
       final GitDir gitDir;
-      (:packagesDir, :processRunner, gitProcessRunner: _, :gitDir) =
+      (:packagesDir, :processRunner, :gitProcessRunner, :gitDir) =
           configureBaseCommandMocks(platform: mockPlatform);
       final BuildExamplesCommand command = BuildExamplesCommand(
         packagesDir,
@@ -998,5 +999,72 @@ void main() {
                 pluginExampleDirectory.path),
           ]));
     });
+
+    group('file filtering', () {
+      const List<String> files = <String>[
+        'pubspec.yaml',
+        'foo.dart',
+        'foo.java',
+        'foo.kt',
+        'foo.m',
+        'foo.swift',
+        'foo.cc',
+        'foo.cpp',
+        'foo.h',
+      ];
+      for (final String file in files) {
+        test('runs command for changes to $file', () async {
+          createFakePackage('package_a', packagesDir);
+
+          gitProcessRunner.mockProcessesForExecutable['git-diff'] =
+              <FakeProcessInfo>[
+            FakeProcessInfo(MockProcess(stdout: '''
+packages/package_a/$file
+''')),
+          ];
+
+          // The target platform is irrelevant here; because this repo's
+          // packages are fully federated, there's no need to distinguish
+          // the ignore list by target (e.g., skipping iOS tests if only Java or
+          // Kotlin files change), because package-level filering will already
+          // accomplish the same goal.
+          final List<String> output = await runCapturingPrint(
+              runner, <String>['build-examples', '--web']);
+
+          expect(
+              output,
+              containsAllInOrder(<Matcher>[
+                contains('Running for package_a'),
+              ]));
+        });
+      }
+
+      test('skips commands if all files should be ignored', () async {
+        createFakePackage('package_a', packagesDir);
+
+        gitProcessRunner.mockProcessesForExecutable['git-diff'] =
+            <FakeProcessInfo>[
+          FakeProcessInfo(MockProcess(stdout: '''
+README.md
+CODEOWNERS
+packages/package_a/CHANGELOG.md
+''')),
+        ];
+
+        final List<String> output =
+            await runCapturingPrint(runner, <String>['build-examples']);
+
+        expect(
+            output,
+            isNot(containsAllInOrder(<Matcher>[
+              contains('Running for package_a'),
+            ])));
+        expect(
+            output,
+            containsAllInOrder(<Matcher>[
+              contains('SKIPPING ALL PACKAGES'),
+            ]));
+      });
+    });
   });
 }