Next step in overload dispatcher refactoring.

tools/dom/scripts/htmldartgenerator.py

Index: tools/dom/scripts/htmldartgenerator.py
diff --git a/tools/dom/scripts/htmldartgenerator.py b/tools/dom/scripts/htmldartgenerator.py
index 46ba4ba34edb21bce4e63a4c2d33b8cea05b974f..d0fc560462708143fd438eba10a3f5e426e12cff 100644
--- a/tools/dom/scripts/htmldartgenerator.py
+++ b/tools/dom/scripts/htmldartgenerator.py
@@ -193,25 +193,57 @@ class HtmlDartGenerator(object):
     else:
       self.EmitOperation(info, method_name)
 
-  def _OverloadChecks(self,
-      operation,
+  def _GenerateDispatcherBody(self,
+      emitter,
+      operations,
       parameter_names,
-      argument_count,
+      generate_call,
+      is_optional,
       can_omit_type_check=lambda type, pos: False):
-    checks = []
-    for i in range(0, argument_count):
-      argument = operation.arguments[i]
-      parameter_name = parameter_names[i]
-      test_type = self._DartType(argument.type.id)
-      if test_type in ['dynamic', 'Object']:
-        checks.append('?%s' % parameter_name)
-      elif not can_omit_type_check(test_type, i):
-        checks.append('(%s is %s || %s == null)' % (
-            parameter_name, test_type, parameter_name))
-    # There can be multiple presence checks.  We need them all since a later
-    # optional argument could have been passed by name, leaving 'holes'.
-    checks.extend(['!?%s' % name for name in parameter_names[argument_count:]])
-    return checks
+
+    def GenerateChecksAndCall(operation, argument_count):
+      checks = []
+      for i in range(0, argument_count):
+        argument = operation.arguments[i]
+        parameter_name = parameter_names[i]
+        test_type = self._DartType(argument.type.id)
+        if test_type in ['dynamic', 'Object']:
+          checks.append('?%s' % parameter_name)
+        elif not can_omit_type_check(test_type, i):
+          checks.append('(%s is %s || %s == null)' % (
+              parameter_name, test_type, parameter_name))
+      # There can be multiple presence checks.  We need them all since a later
+      # optional argument could have been passed by name, leaving 'holes'.
+      checks.extend(['!?%s' % name for name in parameter_names[argument_count:]])
+
+      generate_call(operation, argument_count, checks)
+
+    # TODO: Optimize the dispatch to avoid repeated checks.
+    if len(operations) > 1:
+      for operation in operations:
+        for position, argument in enumerate(operation.arguments):
+          if is_optional(operation, argument):
+            GenerateChecksAndCall(operation, position)
+        GenerateChecksAndCall(operation, len(operation.arguments))
+      emitter.Emit(
+          '    throw new ArgumentError("Incorrect number or type of arguments");'
+          '\n');
+    else:
+      operation = operations[0]
+      argument_count = len(operation.arguments)
+      for position, argument in list(enumerate(operation.arguments))[::-1]:
+        if is_optional(operation, argument):
+          check = '?%s' % parameter_names[position]
+          # argument_count instead of position + 1 is used here to cover one
+          # complicated case with the effectively optional argument in the middle.
+          # Consider foo(x, [Optional] y, [Optional=DefaultIsNullString] z)
+          # (as of now it's modelled after HTMLMediaElement.webkitAddKey).
+          # y is optional in WebCore, while z is not.
+          # In this case, if y was actually passed, we'd like to emit foo(x, y, z) invocation,
+          # not foo(x, y).
+          generate_call(operation, argument_count, [check])
+          argument_count = position
+      generate_call(operation, argument_count, [])
 
   def AdditionalImplementedInterfaces(self):
     # TODO: Include all implemented interfaces, including other Lists.