Add exclude patterns for files and directories

lib/src/cli/format_command.dart

@@ -154,6 +154,13 @@ final class FormatCommand extends Command<int> {
           'See dart.dev/go/experiments.',
       hide: !verbose,
     );
+    argParser.addMultiOption(
+      'exclude',
+      help:
+          'Exclude files and directories matching the given patterns.\n'
+          'Patterns can be file paths, directory names, or glob patterns.',
+      hide: !verbose,
+    );
 
     if (verbose) argParser.addSeparator('Options when formatting from stdin:');
 
@@ -312,6 +319,7 @@ final class FormatCommand extends Command<int> {
     var setExitIfChanged = argResults['set-exit-if-changed'] as bool;
 
     var experimentFlags = argResults['enable-experiment'] as List<String>;
+    var excludePatterns = argResults['exclude'] as List<String>;
 
     // If stdin isn't connected to a pipe, then the user is not passing
     // anything to stdin, so let them know they made a mistake.
@@ -339,6 +347,7 @@ final class FormatCommand extends Command<int> {
       summary: summary,
       setExitIfChanged: setExitIfChanged,
       experimentFlags: experimentFlags,
+      excludePatterns: excludePatterns,
     );
 
     if (argResults.rest.isEmpty) {

lib/src/cli/formatter_options.dart

@@ -54,6 +54,9 @@ final class FormatterOptions {
   /// See dart.dev/go/experiments for details.
   final List<String> experimentFlags;
 
+  /// Patterns for files and directories to exclude from formatting.
+  final List<String> excludePatterns;
+
   FormatterOptions({
     this.languageVersion,
     this.indent = 0,
@@ -65,7 +68,9 @@ final class FormatterOptions {
     this.summary = Summary.none,
     this.setExitIfChanged = false,
     List<String>? experimentFlags,
-  }) : experimentFlags = [...?experimentFlags];
+    List<String>? excludePatterns,
+  }) : experimentFlags = [...?experimentFlags],
+       excludePatterns = [...?excludePatterns];
 
   /// Called when [file] is about to be formatted.
   ///

lib/src/io.dart

@@ -129,6 +129,28 @@ Future<void> formatPaths(FormatterOptions options, List<String> paths) async {
   }
 }
 
+/// Checks if the given [path] matches any of the [excludePatterns].
+bool _isExcluded(String path, List<String> excludePatterns) {
+  var relativePath = p.relative(path);
+  for (var pattern in excludePatterns) {
+    if (relativePath.contains(pattern) || _matchesGlob(relativePath, pattern)) {
+      return true;
+    }
+  }
+  return false;
+}
+
+/// Simple glob matching for patterns like *.dart or **/generated/**.
+bool _matchesGlob(String path, String pattern) {
+  // For simplicity, support basic wildcards: * and **
+  var regexPattern = pattern
+      .replaceAll('.', '\\.')
+      .replaceAll('*', '.*')
+      .replaceAll('**', '.*');
+  var regex = RegExp('^$regexPattern\$');
+  return regex.hasMatch(path);
+}
+
 /// Runs the formatter on every .dart file in [path] (and its subdirectories),
 /// and replaces them with their formatted output.
 ///
@@ -156,6 +178,9 @@ Future<bool> _processDirectory(
     var parts = p.split(p.relative(entry.path, from: directory.path));
     if (parts.any((part) => part.startsWith('.'))) continue;
 
+    // Check if the file should be excluded.
+    if (_isExcluded(entry.path, options.excludePatterns)) continue;
+
     if (!await _processFile(
       cache,
       options,

test/cli/cli_test.dart

@@ -247,4 +247,91 @@ void main() {
       await process.shouldExit(70);
     });
   });
+
+  group('--exclude', () {
+    test('excludes specific files', () async {
+      await d.dir('code', [
+        d.file('a.dart', unformattedSource),
+        d.file('b.dart', unformattedSource),
+        d.file('c.dart', unformattedSource),
+      ]).create();
+
+      var process = await runFormatter(['--exclude', 'b.dart', 'code']);
+      await expectLater(
+        process.stdout,
+        emitsInOrder([
+          'Formatted ${p.join('code', 'a.dart')}',
+          'Formatted ${p.join('code', 'c.dart')}',
+        ]),
+      );
+      await expectLater(
+        process.stdout,
+        emits(startsWith('Formatted 2 files (2 changed)')),
+      );
+      await process.shouldExit(0);
+
+      // b.dart should remain unformatted.
+      await d.dir('code', [
+        d.file('a.dart', formattedSource),
+        d.file('b.dart', unformattedSource),
+        d.file('c.dart', formattedSource),
+      ]).validate();
+    });
+
+    test('excludes directories', () async {
+      await d.dir('code', [
+        d.dir('subdir', [d.file('a.dart', unformattedSource)]),
+        d.file('b.dart', unformattedSource),
+      ]).create();
+
+      var process = await runFormatter(['--exclude', 'subdir', 'code']);
+      await expectLater(
+        process.stdout,
+        emitsInOrder(['Formatted ${p.join('code', 'b.dart')}']),
+      );
+      await expectLater(
+        process.stdout,
+        emits(startsWith('Formatted 1 file (1 changed)')),
+      );
+      await process.shouldExit(0);
+
+      // subdir/a.dart should remain unformatted.
+      await d.dir('code', [
+        d.dir('subdir', [d.file('a.dart', unformattedSource)]),
+        d.file('b.dart', formattedSource),
+      ]).validate();
+    });
+
+    test('supports multiple exclude patterns', () async {
+      await d.dir('code', [
+        d.file('a.dart', unformattedSource),
+        d.file('b.dart', unformattedSource),
+        d.file('c.dart', unformattedSource),
+      ]).create();
+
+      var process = await runFormatter([
+        '--exclude',
+        'a.dart',
+        '--exclude',
+        'c.dart',
+        'code',
+      ]);
+      await expectLater(
+        process.stdout,
+        emitsInOrder(['Formatted ${p.join('code', 'b.dart')}']),
+      );
+      await expectLater(
+        process.stdout,
+        emits(startsWith('Formatted 1 file (1 changed)')),
+      );
+      await process.shouldExit(0);
+
+      // a.dart and c.dart should remain unformatted.
+      await d.dir('code', [
+        d.file('a.dart', unformattedSource),
+        d.file('b.dart', formattedSource),
+        d.file('c.dart', unformattedSource),
+      ]).validate();
+    });
+  });
 }