Check license header in flutter analyze

Author: Jonas Greifenhain

packages/amplify_lints/lib/amplify_lints.dart

@@ -0,0 +1,11 @@
+// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+/// Custom lint rules for Amplify Flutter packages.
+///
+/// This library is the entry point for the custom_lint plugin.
+/// It is automatically discovered by the `custom_lint` package.
+library amplify_lints;
+
+export 'src/lints/missing_license_header.dart' show MissingLicenseHeader;
+export 'src/plugin.dart' show createPlugin;

packages/amplify_lints/lib/app.yaml

@@ -1,6 +1,8 @@
 include: package:flutter_lints/flutter.yaml
 
 analyzer:
+  plugins:
+    - custom_lint
   language:
     strict-casts: true
     strict-inference: true

packages/amplify_lints/lib/library.yaml

@@ -1,6 +1,8 @@
 include: package:lints/recommended.yaml
 
 analyzer:
+  plugins:
+    - custom_lint
   language:
     strict-casts: true
     strict-inference: true

packages/amplify_lints/lib/src/lints/missing_license_header.dart

@@ -0,0 +1,109 @@
+// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+import 'dart:io';
+
+import 'package:analyzer/error/error.dart' show AnalysisError, ErrorSeverity;
+import 'package:analyzer/error/listener.dart';
+import 'package:custom_lint_builder/custom_lint_builder.dart';
+
+/// The expected license header lines.
+const _licenseHeader = [
+  '// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.',
+  '// SPDX-License-Identifier: Apache-2.0',
+];
+
+/// A custom lint rule that checks for the presence of the standard
+/// Amazon/Apache-2.0 license header at the top of every Dart file.
+///
+/// **Good:**
+/// ```dart
+/// // Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+/// // SPDX-License-Identifier: Apache-2.0
+///
+/// library my_library;
+/// ```
+///
+/// **Bad:**
+/// ```dart
+/// library my_library;
+/// ```
+class MissingLicenseHeader extends DartLintRule {
+  /// Creates a new [MissingLicenseHeader] lint rule.
+  const MissingLicenseHeader() : super(code: _code);
+
+  static const _code = LintCode(
+    name: 'missing_license_header',
+    problemMessage:
+        'Dart files must start with the Amazon copyright and Apache-2.0 '
+        'license header.',
+    correctionMessage: 'Add the license header to the top of this file.',
+    errorSeverity: ErrorSeverity.WARNING,
+  );
+
+  @override
+  void run(
+    CustomLintResolver resolver,
+    ErrorReporter reporter,
+    CustomLintContext context,
+  ) {
+    context.registry.addCompilationUnit((node) {
+      final path = resolver.path;
+
+      // Read the raw file content to check for comments (which are not
+      // present in the AST returned by toSource()).
+      final file = File(path);
+      if (!file.existsSync()) return;
+
+      final content = file.readAsStringSync();
+      if (_hasLicenseHeader(content)) return;
+
+      // Report the lint on the first token in the file.
+      final firstToken = node.beginToken;
+      reporter.atToken(firstToken, _code);
+    });
+  }
+
+  @override
+  List<Fix> getFixes() => [_AddLicenseHeaderFix()];
+}
+
+/// Returns `true` if [content] starts with the expected license header.
+bool _hasLicenseHeader(String content) {
+  final lines = content.split('\n');
+  if (lines.length < _licenseHeader.length) return false;
+
+  for (var i = 0; i < _licenseHeader.length; i++) {
+    if (lines[i].trimRight() != _licenseHeader[i]) return false;
+  }
+  return true;
+}
+
+class _AddLicenseHeaderFix extends DartFix {
+  @override
+  void run(
+    CustomLintResolver resolver,
+    ChangeReporter reporter,
+    CustomLintContext context,
+    AnalysisError analysisError,
+    List<AnalysisError> others,
+  ) {
+    context.registry.addCompilationUnit((node) {
+      if (!analysisError.sourceRange.intersects(node.beginToken.sourceRange)) {
+        return;
+      }
+
+      final changeBuilder = reporter.createChangeBuilder(
+        message: 'Add license header',
+        priority: 100,
+      );
+
+      changeBuilder.addDartFileEdit((builder) {
+        builder.addSimpleInsertion(
+          0,
+          '${_licenseHeader.join('\n')}\n\n',
+        );
+      });
+    });
+  }
+}

packages/amplify_lints/lib/src/plugin.dart

@@ -0,0 +1,15 @@
+// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+import 'package:amplify_lints/src/lints/missing_license_header.dart';
+import 'package:custom_lint_builder/custom_lint_builder.dart';
+
+/// Creates the amplify_lints custom lint plugin.
+PluginBase createPlugin() => _AmplifyLints();
+
+class _AmplifyLints extends PluginBase {
+  @override
+  List<LintRule> getLintRules(CustomLintConfigs configs) => [
+        const MissingLicenseHeader(),
+      ];
+}

packages/amplify_lints/pubspec.yaml

@@ -9,5 +9,10 @@ environment:
   sdk: ^3.9.0
 
 dependencies:
+  analyzer: ">=6.0.0 <8.0.0"
+  custom_lint_builder: ^0.7.0
   flutter_lints: ^6.0.0
   lints: ^6.0.0
+
+dev_dependencies:
+  test: ^1.24.0

packages/amplify_lints/test/lints/missing_license_header_test.dart

@@ -0,0 +1,120 @@
+// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+import 'dart:io';
+
+import 'package:amplify_lints/src/lints/missing_license_header.dart';
+import 'package:test/test.dart';
+
+void main() {
+  late Directory tmpDir;
+
+  setUp(() {
+    tmpDir = Directory.systemTemp.createTempSync('license_header_test_');
+  });
+
+  tearDown(() {
+    tmpDir.deleteSync(recursive: true);
+  });
+
+  File _createDartFile(String name, String content) {
+    final file = File('${tmpDir.path}/$name');
+    file.writeAsStringSync(content);
+    return file;
+  }
+
+  group('MissingLicenseHeader', () {
+    const lint = MissingLicenseHeader();
+
+    test('reports lint when license header is missing', () async {
+      final file = _createDartFile(
+        'no_header.dart',
+        'void main() {}\n',
+      );
+
+      final errors = await lint.testAnalyzeAndRun(file);
+      expect(errors, hasLength(1));
+      expect(errors.first.errorCode.name, 'missing_license_header');
+    });
+
+    test('does not report lint when license header is present', () async {
+      final file = _createDartFile(
+        'with_header.dart',
+        '// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.\n'
+        '// SPDX-License-Identifier: Apache-2.0\n'
+        '\n'
+        'void main() {}\n',
+      );
+
+      final errors = await lint.testAnalyzeAndRun(file);
+      expect(errors, isEmpty);
+    });
+
+    test('reports lint when only copyright line is present', () async {
+      final file = _createDartFile(
+        'partial_header.dart',
+        '// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.\n'
+        '\n'
+        'void main() {}\n',
+      );
+
+      final errors = await lint.testAnalyzeAndRun(file);
+      expect(errors, hasLength(1));
+    });
+
+    test('reports lint when only SPDX line is present', () async {
+      final file = _createDartFile(
+        'spdx_only.dart',
+        '// SPDX-License-Identifier: Apache-2.0\n'
+        '\n'
+        'void main() {}\n',
+      );
+
+      final errors = await lint.testAnalyzeAndRun(file);
+      expect(errors, hasLength(1));
+    });
+
+    test('reports lint when header lines are in wrong order', () async {
+      final file = _createDartFile(
+        'wrong_order.dart',
+        '// SPDX-License-Identifier: Apache-2.0\n'
+        '// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.\n'
+        '\n'
+        'void main() {}\n',
+      );
+
+      final errors = await lint.testAnalyzeAndRun(file);
+      expect(errors, hasLength(1));
+    });
+
+    test('allows content after the header', () async {
+      final file = _createDartFile(
+        'full_file.dart',
+        '// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.\n'
+        '// SPDX-License-Identifier: Apache-2.0\n'
+        '\n'
+        "import 'dart:core';\n"
+        '\n'
+        'class Foo {\n'
+        '  void bar() {}\n'
+        '}\n',
+      );
+
+      final errors = await lint.testAnalyzeAndRun(file);
+      expect(errors, isEmpty);
+    });
+
+    test('does not report lint when header has trailing whitespace', () async {
+      final file = _createDartFile(
+        'trailing_ws.dart',
+        '// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.  \n'
+        '// SPDX-License-Identifier: Apache-2.0  \n'
+        '\n'
+        'void main() {}\n',
+      );
+
+      final errors = await lint.testAnalyzeAndRun(file);
+      expect(errors, isEmpty);
+    });
+  });
+}