[pigeon] Add documentation comments to gobject generator

Adds documentation comments to gobject generator to document the custom type id constants
Moves the custom type id constants to be all in one block instead of interleaved

Author: JesseRiemens

packages/pigeon/example/app/linux/messages.g.cc

@@ -128,6 +128,7 @@ G_DEFINE_TYPE(PigeonExamplePackageMessageCodec,
               fl_standard_message_codec_get_type())
 
 const int pigeon_example_package_code_type_id = 129;
+const int pigeon_example_package_message_data_type_id = 130;
 
 static gboolean
 pigeon_example_package_message_codec_write_pigeon_example_package_code(
@@ -138,8 +139,6 @@ pigeon_example_package_message_codec_write_pigeon_example_package_code(
   return fl_standard_message_codec_write_value(codec, buffer, value, error);
 }
 
-const int pigeon_example_package_message_data_type_id = 130;
-
 static gboolean
 pigeon_example_package_message_codec_write_pigeon_example_package_message_data(
     FlStandardMessageCodec* codec, GByteArray* buffer,

packages/pigeon/example/app/linux/messages.g.h

@@ -95,8 +95,14 @@ G_DECLARE_FINAL_TYPE(PigeonExamplePackageMessageCodec,
                      PIGEON_EXAMPLE_PACKAGE, MESSAGE_CODEC,
                      FlStandardMessageCodec)
 
+/**
+ * Custom type ID constants:
+ *
+ * Constants used to identify custom types in the codec.
+ * They are used in the codec to encode and decode custom types.
+ * They may be used in custom object creation functions to identify the type.
+ */
 extern const int pigeon_example_package_code_type_id;
-
 extern const int pigeon_example_package_message_data_type_id;
 
 G_DECLARE_FINAL_TYPE(PigeonExamplePackageExampleHostApi,

packages/pigeon/lib/src/gobject/gobject_generator.dart

@@ -342,9 +342,22 @@ class GObjectHeaderGenerator
     final Iterable<EnumeratedType> customTypes =
         getEnumeratedTypes(root, excludeSealedClasses: true);
 
+    if (customTypes.isNotEmpty) {
+      indent.newln();
+      addDocumentationComments(
+          indent,
+          <String>[
+            'Custom type ID constants:',
+            '',
+            'Constants used to identify custom types in the codec.',
+            'They are used in the codec to encode and decode custom types.',
+            'They may be used in custom object creation functions to identify the type.',
+          ],
+          _docCommentSpec);
+    }
+
     for (final EnumeratedType customType in customTypes) {
       final String customTypeId = _getCustomTypeId(module, customType);
-      indent.newln();
       indent.writeln('extern const int $customTypeId;');
     }
   }
@@ -1028,15 +1041,18 @@ class GObjectSourceGenerator
     _writeDefineType(indent, module, _codecBaseName,
         parentType: 'fl_standard_message_codec_get_type()');
 
+    indent.newln();
+    for (final EnumeratedType customType in customTypes) {
+      final String customTypeId = _getCustomTypeId(module, customType);
+      indent.writeln('const int $customTypeId = ${customType.enumeration};');
+    }
+
     for (final EnumeratedType customType in customTypes) {
       final String customTypeName = _getClassName(module, customType.name);
       final String snakeCustomTypeName =
           _snakeCaseFromCamelCase(customTypeName);
       final String customTypeId = _getCustomTypeId(module, customType);
 
-      indent.newln();
-      indent.writeln('const int $customTypeId = ${customType.enumeration};');
-
       indent.newln();
       final String valueType = customType.type == CustomTypes.customClass
           ? '$customTypeName*'

packages/pigeon/platform_tests/test_plugin/linux/pigeon/core_tests.gen.cc

@@ -2418,6 +2418,14 @@ G_DEFINE_TYPE(CoreTestsPigeonTestMessageCodec,
               fl_standard_message_codec_get_type())
 
 const int core_tests_pigeon_test_an_enum_type_id = 129;
+const int core_tests_pigeon_test_another_enum_type_id = 130;
+const int core_tests_pigeon_test_unused_class_type_id = 131;
+const int core_tests_pigeon_test_all_types_type_id = 132;
+const int core_tests_pigeon_test_all_nullable_types_type_id = 133;
+const int core_tests_pigeon_test_all_nullable_types_without_recursion_type_id =
+    134;
+const int core_tests_pigeon_test_all_classes_wrapper_type_id = 135;
+const int core_tests_pigeon_test_test_message_type_id = 136;
 
 static gboolean
 core_tests_pigeon_test_message_codec_write_core_tests_pigeon_test_an_enum(
@@ -2428,8 +2436,6 @@ core_tests_pigeon_test_message_codec_write_core_tests_pigeon_test_an_enum(
   return fl_standard_message_codec_write_value(codec, buffer, value, error);
 }
 
-const int core_tests_pigeon_test_another_enum_type_id = 130;
-
 static gboolean
 core_tests_pigeon_test_message_codec_write_core_tests_pigeon_test_another_enum(
     FlStandardMessageCodec* codec, GByteArray* buffer, FlValue* value,
@@ -2439,8 +2445,6 @@ core_tests_pigeon_test_message_codec_write_core_tests_pigeon_test_another_enum(
   return fl_standard_message_codec_write_value(codec, buffer, value, error);
 }
 
-const int core_tests_pigeon_test_unused_class_type_id = 131;
-
 static gboolean
 core_tests_pigeon_test_message_codec_write_core_tests_pigeon_test_unused_class(
     FlStandardMessageCodec* codec, GByteArray* buffer,
@@ -2452,8 +2456,6 @@ core_tests_pigeon_test_message_codec_write_core_tests_pigeon_test_unused_class(
   return fl_standard_message_codec_write_value(codec, buffer, values, error);
 }
 
-const int core_tests_pigeon_test_all_types_type_id = 132;
-
 static gboolean
 core_tests_pigeon_test_message_codec_write_core_tests_pigeon_test_all_types(
     FlStandardMessageCodec* codec, GByteArray* buffer,
@@ -2464,8 +2466,6 @@ core_tests_pigeon_test_message_codec_write_core_tests_pigeon_test_all_types(
   return fl_standard_message_codec_write_value(codec, buffer, values, error);
 }
 
-const int core_tests_pigeon_test_all_nullable_types_type_id = 133;
-
 static gboolean
 core_tests_pigeon_test_message_codec_write_core_tests_pigeon_test_all_nullable_types(
     FlStandardMessageCodec* codec, GByteArray* buffer,
@@ -2477,9 +2477,6 @@ core_tests_pigeon_test_message_codec_write_core_tests_pigeon_test_all_nullable_t
   return fl_standard_message_codec_write_value(codec, buffer, values, error);
 }
 
-const int core_tests_pigeon_test_all_nullable_types_without_recursion_type_id =
-    134;
-
 static gboolean
 core_tests_pigeon_test_message_codec_write_core_tests_pigeon_test_all_nullable_types_without_recursion(
     FlStandardMessageCodec* codec, GByteArray* buffer,
@@ -2494,8 +2491,6 @@ core_tests_pigeon_test_message_codec_write_core_tests_pigeon_test_all_nullable_t
   return fl_standard_message_codec_write_value(codec, buffer, values, error);
 }
 
-const int core_tests_pigeon_test_all_classes_wrapper_type_id = 135;
-
 static gboolean
 core_tests_pigeon_test_message_codec_write_core_tests_pigeon_test_all_classes_wrapper(
     FlStandardMessageCodec* codec, GByteArray* buffer,
@@ -2507,8 +2502,6 @@ core_tests_pigeon_test_message_codec_write_core_tests_pigeon_test_all_classes_wr
   return fl_standard_message_codec_write_value(codec, buffer, values, error);
 }
 
-const int core_tests_pigeon_test_test_message_type_id = 136;
-
 static gboolean
 core_tests_pigeon_test_message_codec_write_core_tests_pigeon_test_test_message(
     FlStandardMessageCodec* codec, GByteArray* buffer,

packages/pigeon/platform_tests/test_plugin/linux/pigeon/core_tests.gen.h

@@ -1433,21 +1433,21 @@ G_DECLARE_FINAL_TYPE(CoreTestsPigeonTestMessageCodec,
                      CORE_TESTS_PIGEON_TEST, MESSAGE_CODEC,
                      FlStandardMessageCodec)
 
+/**
+ * Custom type ID constants:
+ *
+ * Constants used to identify custom types in the codec.
+ * They are used in the codec to encode and decode custom types.
+ * They may be used in custom object creation functions to identify the type.
+ */
 extern const int core_tests_pigeon_test_an_enum_type_id;
-
 extern const int core_tests_pigeon_test_another_enum_type_id;
-
 extern const int core_tests_pigeon_test_unused_class_type_id;
-
 extern const int core_tests_pigeon_test_all_types_type_id;
-
 extern const int core_tests_pigeon_test_all_nullable_types_type_id;
-
 extern const int
     core_tests_pigeon_test_all_nullable_types_without_recursion_type_id;
-
 extern const int core_tests_pigeon_test_all_classes_wrapper_type_id;
-
 extern const int core_tests_pigeon_test_test_message_type_id;
 
 G_DECLARE_FINAL_TYPE(CoreTestsPigeonTestHostIntegrationCoreApi,