Use nested emitter idiom.

lib/dom/scripts/systemnative.py

 #!/usr/bin/python
 # Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 # for details. All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 
 """This module provides shared functionality for the systems to generate
 native binding from the IDL database."""
 
 import emitter
 import os
@@ skipping 709 matching lines @@
     if 'synthesizedV8EnabledAtRuntime' in ext_attrs:
       raises_exceptions = True
       self._cpp_impl_includes.add('"RuntimeEnabledFeatures.h"')
       runtime_check = emitter.Format(
           '        if (!RuntimeEnabledFeatures::$(FEATURE)Enabled()) {\n'
           '            exception = Dart_NewString("Feature $FEATURE is not enabled");\n'
           '            goto fail;\n'
           '        }',
           FEATURE=_ToWebKitName(ext_attrs['synthesizedV8EnabledAtRuntime']))
 
-    head_emitter = emitter.Emitter()
+    body_emitter = self._cpp_definitions_emitter.Emit(
+        '\n'
+        'static void $CALLBACK_NAME(Dart_NativeArguments args)\n'
+        '{\n'
+        '    DartApiScope dartApiScope;\n'
+        '$!BODY'
+        '}\n',
+        CALLBACK_NAME=callback_name)
+
+    if raises_exceptions:
+      body_emitter = body_emitter.Emit(
+          '    Dart_Handle exception = 0;\n'
+          '$!BODY'
+          '\n'
+          'fail:\n'
+          '    Dart_ThrowException(exception);\n'
+          '    ASSERT_NOT_REACHED();\n')
+
+    body_emitter = body_emitter.Emit(
+        '    {\n'
+        '$!BODY'
+        '        return;\n'
+        '    }\n')
 
     if requires_v8_scope:
-      head_emitter.Emit(
+      body_emitter.Emit(
           '        V8Scope v8scope;\n\n')
 
     if runtime_check:
-      head_emitter.Emit(
+      body_emitter.Emit(
           '$RUNTIME_CHECK\n',
           RUNTIME_CHECK=runtime_check)
 
     if requires_script_execution_context:
-      head_emitter.Emit(
+      body_emitter.Emit(
           '        ScriptExecutionContext* context = DartUtilities::scriptExecutionContext();\n'
           '        if (!context) {\n'
           '            exception = Dart_NewString("Failed to retrieve a context");\n'
           '            goto fail;\n'
           '        }\n\n')
 
     if requires_dom_window:
-      head_emitter.Emit(
+      body_emitter.Emit(
           '        DOMWindow* domWindow = DartUtilities::domWindowForCurrentIsolate();\n'
           '        if (!domWindow) {\n'
           '            exception = Dart_NewString("Failed to fetch domWindow");\n'
           '            goto fail;\n'
           '        }\n'
           '        Document* document = domWindow->document();\n')
 
     if needs_receiver:
-      head_emitter.Emit(
+      body_emitter.Emit(
           '        $WEBCORE_CLASS_NAME* receiver = DartDOMWrapper::receiver< $WEBCORE_CLASS_NAME >(args);\n',
           WEBCORE_CLASS_NAME=self._interface_type_info.native_type())
 
     if requires_stack_info:
-      head_emitter.Emit(
+      body_emitter.Emit(
           '\n'
           '        Dart_Handle customArgument = Dart_GetNativeArgument(args, $INDEX);\n'
           '        RefPtr<ScriptArguments> scriptArguments(DartUtilities::createScriptArguments(customArgument, exception));\n'
           '        if (!scriptArguments)\n'
           '            goto fail;\n'
           '        RefPtr<ScriptCallStack> scriptCallStack(DartUtilities::createScriptCallStack());\n'
           '        if (!scriptCallStack->size())\n'
           '            return;\n',
           INDEX=len(arguments))
 
     # Process Dart cpp_arguments.
     start_index = 0
     if needs_receiver:
       start_index = 1
     for (i, argument) in enumerate(arguments):
       if (i == len(arguments) - 1 and
           self._interface.id == 'Console' and
           argument.id == 'arg'):
         # FIXME: we are skipping last argument here because it was added in
         # supplemental dart.idl. Cleanup dart.idl and remove this check.
         break
-      argument_expression = self._GenerateToNative(head_emitter, argument, start_index + i)
+      argument_expression = self._GenerateToNative(body_emitter, argument, start_index + i)
       cpp_arguments.append(argument_expression)
 
-    head_emitter.Emit('\n')
+    body_emitter.Emit('\n')
 
     # FIXME: rework in IDLs.
     if node.id in ['addEventListener', 'removeEventListener']:
       # addEventListener's and removeEventListener's last argument is marked
       # as optional in idl, but is not optional in webcore implementation.
       if len(arguments) == 2:
         cpp_arguments.append('false')
 
     if self._interface.id == 'CSSStyleDeclaration' and node.id == 'setProperty':
       # CSSStyleDeclaration.setProperty priority parameter is optional in Dart
       # idl, but is not optional in webcore implementation.
       if len(arguments) == 2:
         cpp_arguments.append('String()')
 
     if 'NeedsUserGestureCheck' in ext_attrs:
       cpp_arguments.append('DartUtilities::processingUserGesture');
 
-    invocation_emitter = head_emitter
+    invocation_emitter = body_emitter
     if raises_dom_exception:
       cpp_arguments.append('ec')
-      invocation_emitter = head_emitter.Emit(
+      invocation_emitter = body_emitter.Emit(
         '        ExceptionCode ec = 0;\n'
         '$!INVOCATION'
         '        if (UNLIKELY(ec)) {\n'
         '            exception = DartDOMWrapper::exceptionCodeToDartException(ec);\n'
         '            goto fail;\n'
         '        }\n')
 
     function_call = '%s(%s)' % (function_expression, ', '.join(cpp_arguments))
     if return_type == 'void':
       invocation_emitter.Emit(
         '        $FUNCTION_CALL;\n',
         FUNCTION_CALL=function_call)
     else:
       return_type_info = self._TypeInfo(return_type)
       self._cpp_impl_includes |= set(return_type_info.conversion_includes())
 
       # Generate to Dart conversion of C++ value.
       to_dart_conversion = return_type_info.to_dart_conversion(function_call, self._interface.id, ext_attrs)
       invocation_emitter.Emit(
         '        Dart_Handle returnValue = $TO_DART_CONVERSION;\n'
         '        if (returnValue)\n'
         '            Dart_SetReturnValue(args, returnValue);\n',
         TO_DART_CONVERSION=to_dart_conversion)
 
-    body = emitter.Format(
-        '    {\n'
-        '$HEAD'
-        '        return;\n'
-        '    }\n',
-        HEAD=head_emitter.Fragments())
-
-    if raises_exceptions:
-      body = emitter.Format(
-          '    Dart_Handle exception = 0;\n'
-          '$BODY'
-          '\n'
-          'fail:\n'
-          '    Dart_ThrowException(exception);\n'
-          '    ASSERT_NOT_REACHED();\n',
-          BODY=body)
-
-    self._cpp_definitions_emitter.Emit(
-        '\n'
-        'static void $CALLBACK_NAME(Dart_NativeArguments args)\n'
-        '{\n'
-        '    DartApiScope dartApiScope;\n'
-        '$BODY'
-        '}\n',
-        CALLBACK_NAME=callback_name,
-        BODY=body)
-
   def _GenerateToNative(self, emitter, idl_node, index):
     """idl_node is IDLArgument or IDLAttribute."""
     type_info = self._TypeInfo(idl_node.type.id)
     self._cpp_impl_includes |= set(type_info.to_native_includes())
     argument_name = idl_node.id
     # Rename to get rid of conflicts with C++ keywords.
     if argument_name == 'default':
       argument_name = 'value'
     handle = 'Dart_GetNativeArgument(args, %i)' % index
     argument_expression = type_info.emit_to_native(
@@ skipping 65 matching lines @@
 
 def _IsArgumentOptionalInWebCore(argument):
   return IsOptional(argument) and not 'Callback' in argument.ext_attrs
 
 def _ToWebKitName(name):
   name = name[0].lower() + name[1:]
   name = re.sub(r'^(hTML|uRL|jS|xML|xSLT)', lambda s: s.group(1).lower(),
                 name)
   return re.sub(r'^(create|exclusive)', lambda s: 'is' + s.group(1).capitalize(),
                 name)