[pigeon] Report a clear error for enhanced enums

packages/pigeon/CHANGELOG.md

@@ -1,3 +1,9 @@
+## 27.1.2
+
+* Reports a clear error when an input file uses an enhanced enum (one with a
+  constructor, fields, methods, or arguments on its values), instead of
+  silently generating incorrect output.
+
 ## 27.1.1
 
 * [dart] Adds usage documentation to generated event channel methods, and

packages/pigeon/lib/src/generator_tools.dart

@@ -15,7 +15,7 @@ import 'generator.dart';
 /// The current version of pigeon.
 ///
 /// This must match the version in pubspec.yaml.
-const String pigeonVersion = '27.1.1';
+const String pigeonVersion = '27.1.2';
 
 /// Default plugin package name.
 const String defaultPluginPackageName = 'dev.flutter.pigeon';

packages/pigeon/lib/src/pigeon_lib_internal.dart

@@ -1747,6 +1747,26 @@ class RootBuilder extends dart_ast_visitor.RecursiveAstVisitor<Object?> {
 
   @override
   Object? visitEnumDeclaration(dart_ast.EnumDeclaration node) {
+    // Enhanced enums (those with a constructor, fields, methods, or arguments
+    // on their values) aren't supported by Pigeon.
+    final bool isEnhancedEnum =
+        node.body.members.isNotEmpty ||
+        node.body.constants.any((dart_ast.EnumConstantDeclaration e) => e.arguments != null) ||
+        node.namePart.typeParameters != null ||
+        node.namePart is dart_ast.PrimaryConstructorDeclaration ||
+        node.withClause != null ||
+        node.implementsClause != null;
+    if (isEnhancedEnum) {
+      _errors.add(
+        Error(
+          message:
+              'Pigeon doesn\'t support enhanced enums ("${node.namePart.typeName.lexeme}"). '
+              'Use a plain enum without a constructor, fields, methods, type parameters, '
+              'mixins, interfaces, or arguments on its values.',
+          lineNumber: calculateLineNumber(source, node.offset),
+        ),
+      );
+    }
     _enums.add(
       Enum(
         name: node.namePart.typeName.lexeme,
@@ -1761,7 +1781,12 @@ class RootBuilder extends dart_ast_visitor.RecursiveAstVisitor<Object?> {
         documentationComments: _documentationCommentsParser(node.documentationComment?.tokens),
       ),
     );
-    node.visitChildren(this);
+    // Don't visit the children of an enhanced enum: the declaration is
+    // already reported as unsupported, and the visitor doesn't expect
+    // class-like members outside of a class.
+    if (!isEnhancedEnum) {
+      node.visitChildren(this);
+    }
     return null;
   }
 

packages/pigeon/pubspec.yaml

@@ -2,7 +2,7 @@ name: pigeon
 description: Code generator tool to make communication between Flutter and the host platform type-safe and easier.
 repository: https://github.com/flutter/packages/tree/main/packages/pigeon
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+pigeon%22
-version: 27.1.1 # This must match the version in lib/src/generator_tools.dart
+version: 27.1.2 # This must match the version in lib/src/generator_tools.dart
 
 environment:
   sdk: ^3.10.0

packages/pigeon/test/pigeon_lib_test.dart

@@ -276,6 +276,125 @@ abstract class Api {
     expect(results.root.classes[0].fields[0].name, equals('enum1'));
   });
 
+  test('enhanced enum with a constructor and fields is an error', () {
+    const code = '''
+enum Enum1 {
+  one(1),
+  two(2);
+
+  const Enum1(this.value);
+  final int value;
+}
+
+class ClassWithEnum {
+  Enum1? enum1;
+}
+
+@HostApi
+abstract class Api {
+  ClassWithEnum foo();
+}
+''';
+    final ParseResults results = parseSource(code);
+    expect(results.errors, hasLength(1));
+    expect(results.errors[0].message, contains('enhanced enums'));
+    expect(results.errors[0].message, contains('Enum1'));
+  });
+
+  test('enum with a mixin or interface is an error', () {
+    const code = '''
+mixin Mixin1 {}
+
+abstract class Interface1 {}
+
+enum Enum1 with Mixin1 implements Interface1 {
+  one,
+  two,
+}
+
+class ClassWithEnum {
+  Enum1? enum1;
+}
+
+@HostApi
+abstract class Api {
+  ClassWithEnum foo();
+}
+''';
+    final ParseResults results = parseSource(code);
+    expect(results.errors, hasLength(1));
+    expect(results.errors[0].message, contains('enhanced enums'));
+    expect(results.errors[0].message, contains('Enum1'));
+  });
+
+  test('plain enum with a trailing semicolon is not an error', () {
+    const code = '''
+enum Enum1 {
+  one,
+  two;
+}
+
+class ClassWithEnum {
+  Enum1? enum1;
+}
+
+@HostApi
+abstract class Api {
+  ClassWithEnum foo();
+}
+''';
+    final ParseResults results = parseSource(code);
+    expect(results.errors, isEmpty);
+  });
+
+  test('enhanced enum with a getter is an error and does not crash', () {
+    const code = '''
+enum Enum1 {
+  one(1),
+  two(2);
+
+  const Enum1(this.value);
+  final int value;
+  int get doubled => value * 2;
+}
+
+class ClassWithEnum {
+  Enum1? enum1;
+}
+
+@HostApi
+abstract class Api {
+  ClassWithEnum foo();
+}
+''';
+    final ParseResults results = parseSource(code);
+    expect(results.errors, hasLength(1));
+    expect(results.errors[0].message, contains('enhanced enums'));
+    expect(results.errors[0].message, contains('Enum1'));
+  });
+
+  test('enum with arguments on its values is an error', () {
+    const code = '''
+enum Enum1 {
+  one(1),
+  two(2);
+}
+
+class ClassWithEnum {
+  Enum1? enum1;
+}
+
+@HostApi
+abstract class Api {
+  ClassWithEnum foo();
+}
+''';
+    final ParseResults results = parseSource(code);
+    expect(results.errors, hasLength(1));
+    expect(results.errors[0].message, contains('enhanced enums'));
+    expect(results.errors[0].message, contains('Enum1'));
+  });
+
   test('two methods', () {
     const code = '''
 class Input1 {