IDL: Support optional argument default value syntax

Source/bindings/scripts/idl_definitions.py

Index: Source/bindings/scripts/idl_definitions.py
diff --git a/Source/bindings/scripts/idl_definitions.py b/Source/bindings/scripts/idl_definitions.py
index 2230c8f6e207153d8145a7d7dca1560077f1bf7b..7df366c7c34748a3c3476df947a271b5afa6e6f0 100644
--- a/Source/bindings/scripts/idl_definitions.py
+++ b/Source/bindings/scripts/idl_definitions.py
@@ -475,6 +475,7 @@ class IdlArgument(TypedObject):
         self.is_optional = node.GetProperty('OPTIONAL')  # syntax: (optional T)
         self.is_variadic = False  # syntax: (T...)
         self.name = node.GetName()
+        self.default_value = None
 
         children = node.GetChildren()
         for child in children:
@@ -488,6 +489,8 @@ class IdlArgument(TypedObject):
                 if child_name != '...':
                     raise ValueError('Unrecognized Argument node; expected "...", got "%s"' % child_name)
                 self.is_variadic = child.GetProperty('ELLIPSIS') or False
+            elif child_class == 'Default':
+                self.default_value = IdlDefaultValue(child)
             else:
                 raise ValueError('Unrecognized node class: %s' % child_class)
 
@@ -503,6 +506,23 @@ def arguments_node_to_arguments(node):
             for argument_node in node.GetChildren()]
 
 
+class IdlDefaultValue(TypedObject):

[Nils Barth (inactive), 2014/06/04 05:22:24]

You don't need TypedObject here I don't think:
TypedObject is only for resolving typedefs,
and typedefs aren't applicable to *literals*.

E.g., even if you had
foo(TypeDef x = "bar")
here you're only using "bar" (and the TYPE property in the AST),
not the type of the argument.

Also this can more generically be called IdlLiteral, so I'd write this:
class IdlLiteral(object):
    ...
(In principle this could be used for constants as well,
but those are in practice very simple, so no need.)

Also could you update the class diagram in the module docstring at top?

+    def __init__(self, node):
+        self.value_type = node.GetProperty('TYPE')

[Nils Barth (inactive), 2014/06/04 05:22:24]

Naming: idl_type, rather than value_type.
(might need a bit of converting)

+        if self.value_type == 'DOMString':

[Nils Barth (inactive), 2014/06/04 05:22:24]

Could you factor out this evaluation into a function?

if idl_type == 'DOMString':
    return node.GetProperty('NAME')
if ...:
    ...
raise ...
...has simpler flow

+            self.value = node.GetProperty('NAME')
+        elif self.value_type == 'integer':
+            self.value = eval(node.GetProperty('NAME'))

[Nils Barth (inactive), 2014/06/04 05:22:24]

!!!
Could you please use constructors int() and float()?
...as eval() causes conniptions and hives.

[Jens Widell, 2014/06/04 06:12:18]

Using eval() here is clearly ridiculous. Sorry about that.

I think I meant to handle integer and float using the same expression  in which
case eval() at least added something (but then realized one used NAME and the
other VALUE, and didn't.)

[Nils Barth (inactive), 2014/06/04 06:33:35]

n/p, that makes sense -- I was wondering what exactly you were on,
and this explains it!

+        elif self.value_type == 'float':
+            self.value = eval(node.GetProperty('VALUE'))

[Nils Barth (inactive), 2014/06/04 05:22:24]

Could you add a FIXME for the irregular upstream treatment of NAME/VALUE?

+        elif self.value_type == 'boolean':
+            self.value = node.GetProperty('VALUE')
+        elif self.value_type == 'NULL':

[Nils Barth (inactive), 2014/06/04 05:22:24]

Handling null and undefined will be a bit ugly.
We'd handle this by having properties is_null and is_undefined
(like IdlType.is_nullable).

Cleanest would be to have IdlLiteralNull and IdlLiteralUndefined
which inherit from IdlLiteral
and just override the value for is_null and is_undefined,
respectively.

In that case you'd also need to use a factory function:
default_node_to_idl_literal
...instead of calling the IdlLiteral constructor directly.

+            self.value = None
+        else:
+            raise ValueError('Unrecognized default value type: %s' % self.value_type)
+
+
 ################################################################################
 # Extended attributes
 ################################################################################