Speed up clang-tidy script by skipping third_party files

tools/clang_tidy/lib/clang_tidy.dart

@@ -110,7 +110,7 @@ class ClangTidy {
     final List<dynamic> buildCommandsData = jsonDecode(
       options.buildCommandsPath.readAsStringSync(),
     ) as List<dynamic>;
-    final List<Command> changedFileBuildCommands = getLintCommandsForChangedFiles(
+    final List<Command> changedFileBuildCommands = await getLintCommandsForChangedFiles(
       buildCommandsData,
       changedFiles,
     );
@@ -165,20 +165,20 @@ class ClangTidy {
   /// Given a build commands json file, and the files with local changes,
   /// compute the lint commands to run.
   @visibleForTesting
-  List<Command> getLintCommandsForChangedFiles(
+  Future<List<Command>> getLintCommandsForChangedFiles(
     List<dynamic> buildCommandsData,
     List<io.File> changedFiles,
-  ) {
-    final List<Command> buildCommands = <Command>[
-      for (final dynamic c in buildCommandsData)
-        Command.fromMap(c as Map<String, dynamic>),
-    ];
-
-    return <Command>[
-      for (final Command c in buildCommands)
-        if (c.containsAny(changedFiles))
-          c,
-    ];
+  ) async {
+    final List<Command> buildCommands = <Command>[];
+    for (final dynamic data in buildCommandsData) {
+      final Command command = Command.fromMap(data as Map<String, dynamic>);
+      final LintAction lintAction = await command.lintAction;
+      // Short-circuit the expensive containsAny call for the many third_party files.
+      if (lintAction != LintAction.skipThirdParty && command.containsAny(changedFiles)) {
+        buildCommands.add(command);
+      }
+    }
+    return buildCommands;
   }
 
   Future<_ComputeJobsResult> _computeJobs(
@@ -212,6 +212,9 @@ class ClangTidy {
         case LintAction.skipThirdParty:
           _outSink.writeln('🔷 ignoring $relativePath (third_party)');
           break;
+        case LintAction.skipMissing:
+          _outSink.writeln('🔷 ignoring $relativePath (missing)');
+          break;
       }
     }
     return _ComputeJobsResult(jobs, sawMalformed);
@@ -239,5 +242,3 @@ class ClangTidy {
     return result;
   }
 }
-
-

tools/clang_tidy/lib/src/command.dart

@@ -26,6 +26,9 @@ enum LintAction {
 
   /// Fail due to a malformed FLUTTER_NOLINT comment.
   failMalformedNoLint,
+
+  /// Ignore because the file doesn't exist locally.
+  skipMissing,
 }
 
 /// A compilation command and methods to generate the lint command and job for
@@ -86,20 +89,20 @@ class Command {
     r'//\s*FLUTTER_NOLINT(: https://github.com/flutter/flutter/issues/\d+)?',
   );
 
-  LintAction? _lintAction;
-
   /// The type of lint that is appropriate for this command.
-  Future<LintAction> get lintAction async =>
-    _lintAction ??= await getLintAction(filePath);
+  late final Future<LintAction> lintAction = getLintAction(filePath);
 
   /// Determine the lint action for the file at `path`.
   @visibleForTesting
-  static Future<LintAction> getLintAction(String filePath) {
+  static Future<LintAction> getLintAction(String filePath) async {
     if (path.split(filePath).contains('third_party')) {
-      return Future<LintAction>.value(LintAction.skipThirdParty);
+      return LintAction.skipThirdParty;
     }
 
     final io.File file = io.File(filePath);
+    if (!file.existsSync()) {
+      return LintAction.skipMissing;
+    }
     final Stream<String> lines = file.openRead()
       .transform(utf8.decoder)
       .transform(const LineSplitter());

tools/clang_tidy/test/clang_tidy_test.dart

@@ -106,7 +106,7 @@ Future<int> main(List<String> args) async {
       <String>[
         '--compile-commands',
         // This just has to exist.
-        io.Platform.executable,
+        io.Platform.script.path,
         '--repo',
         '/does/not/exist',
       ],
@@ -168,7 +168,7 @@ Future<int> main(List<String> args) async {
         'file': filePath,
       },
     ];
-    final List<Command> commands = clangTidy.getLintCommandsForChangedFiles(
+    final List<Command> commands = await clangTidy.getLintCommandsForChangedFiles(
       buildCommandsData,
       <io.File>[],
     );
@@ -186,15 +186,17 @@ Future<int> main(List<String> args) async {
       outSink: outBuffer,
       errSink: errBuffer,
     );
-    const String filePath = '/path/to/a/source_file.cc';
+
+    // This just has to exist.
+    final String filePath = io.Platform.script.path;
     final List<dynamic> buildCommandsData = <Map<String, dynamic>>[
       <String, dynamic>{
         'directory': '/unused',
         'command': '../../buildtools/mac-x64/clang/bin/clang $filePath',
         'file': filePath,
       },
     ];
-    final List<Command> commands = clangTidy.getLintCommandsForChangedFiles(
+    final List<Command> commands = await clangTidy.getLintCommandsForChangedFiles(
       buildCommandsData,
       <io.File>[io.File(filePath)],
     );
@@ -220,6 +222,14 @@ Future<int> main(List<String> args) async {
     expect(lintAction, equals(LintAction.skipThirdParty));
   });
 
+  test('Command getLintAction flags missing files', () async {
+    final LintAction lintAction = await Command.getLintAction(
+      'does/not/exist',
+    );
+
+    expect(lintAction, equals(LintAction.skipMissing));
+  });
+
   test('Command getLintActionFromContents flags FLUTTER_NOLINT', () async {
     final LintAction lintAction = await Command.lintActionFromContents(
       Stream<String>.fromIterable(<String>[