[pigeon] Made using enums in type arguments an error, added workaround (#527)

packages/pigeon/CHANGELOG.md

@@ -1,6 +1,9 @@
-## NEXT
+## 1.0.11
 
-* [ci] Started transitioning to a Dart test runner, added windows support.
+* [ci] Starts transition to a Dart test runner, adds windows support.
+* [front-end] Starts issuing an error if enums are used in type arguments.
+* [front-end] Passes through all enums, referenced or not so they can be used as
+  a work around for direct enum support.
 
 ## 1.0.10
 

packages/pigeon/lib/generator_tools.dart

@@ -8,7 +8,7 @@ import 'dart:mirrors';
 import 'ast.dart';
 
 /// The current version of pigeon. This must match the version in pubspec.yaml.
-const String pigeonVersion = '1.0.10';
+const String pigeonVersion = '1.0.11';
 
 /// Read all the content from [stdin] to a String.
 String readStdin() {

packages/pigeon/lib/pigeon_lib.dart

@@ -423,6 +423,13 @@ List<Error> _validateAst(Root root, String source) {
               lineNumber: _calculateLineNumberNullable(source, field.offset),
             ));
           }
+          if (customEnums.contains(typeArgument.baseName)) {
+            result.add(Error(
+              message:
+                  'Enum types aren\'t supported in type arguments in "${field.name}" in class "${klass.name}".',
+              lineNumber: _calculateLineNumberNullable(source, field.offset),
+            ));
+          }
         }
       }
       if (!(validTypes.contains(field.type.baseName) ||
@@ -544,9 +551,6 @@ class _RootBuilder extends dart_ast_visitor.RecursiveAstVisitor<Object?> {
         .removeWhere((Class x) => !referencedTypeNames.contains(x.name));
 
     final List<Enum> referencedEnums = List<Enum>.from(_enums);
-    referencedEnums.removeWhere(
-        (final Enum anEnum) => !referencedTypeNames.contains(anEnum.name));
-
     final Root completeRoot =
         Root(apis: _apis, classes: referencedClasses, enums: referencedEnums);
 

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/master/packages/pigeon
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3Apigeon
-version: 1.0.10 # This must match the version in lib/generator_tools.dart
+version: 1.0.11 # This must match the version in lib/generator_tools.dart
 
 environment:
   sdk: '>=2.12.0 <3.0.0'

packages/pigeon/test/pigeon_lib_test.dart

@@ -901,4 +901,49 @@ abstract class Api {
     final ParseResults results = _parseSource(code);
     expect(results.errors.length, 0);
   });
+
+  test('Enum key not supported', () {
+    const String code = '''
+enum MessageKey {
+  title,
+  subtitle,
+  description,
+}
+
+class Message {
+  int? id;
+  Map<MessageKey?, String?>? additionalProperties;
+}
+
+@HostApi()
+abstract class HostApiBridge {
+  void sendMessage(Message message);
+}
+''';
+    final ParseResults results = _parseSource(code);
+    expect(results.errors.length, 1);
+  });
+
+  test('Export unreferenced enums', () {
+    const String code = '''
+enum MessageKey {
+  title,
+  subtitle,
+  description,
+}
+
+class Message {
+  int? id;
+  Map<int?, String?>? additionalProperties;
+}
+
+@HostApi()
+abstract class HostApiBridge {
+  void sendMessage(Message message);
+}
+''';
+    final ParseResults results = _parseSource(code);
+    expect(results.root.enums.length, 1);
+    expect(results.root.enums[0].name, 'MessageKey');
+  });
 }