[webkit-dev] js binding: function argument type checking

Mo, Zhenyao zhenyao at gmail.com
Wed Aug 11 23:10:24 PDT 2010

Actually it's a different issue.  What we want to do is not enforcing
full arguments, but if an input argument is the wrong type, we raise a


On Wed, Aug 11, 2010 at 7:13 PM, Adam Barth <abarth at webkit.org> wrote:
> This sounds related to the recent addition of
> [RequiresAllArguments=Raise].  Historically, we've been lax about
> missing arguments.  I think the specs want us to be stricter, but last
> time we discussed the topic, the read I got was that the compatibility
> pain might not be worth the benefit.
> Adam
> On Wed, Aug 11, 2010 at 7:06 PM, Mo, Zhenyao <zhenyao at gmail.com> wrote:
>> Currently for a function's signature in WebKit, if an argument's type
>> is a wrapper type (those JS objec ts that wrap c++ objects, for
>> example, JSWebGLProgram, JSCSSRule, etc.) and if the input object's
>> type does not match the signature, the input is casted to null and no
>> TypeError is raised.
>> Even though WebKit doesn't use Web IDL specially, I think we can look
>> to the Web IDL spec for guidance on what the behavior should be.
>> According to Web IDL spec (http://dev.w3.org/2006/webapi/WebIDL/),
>> unless [AllowAny] is put in the signature, an TypeError should be
>> raised if an argument type does not match its signature.  The new
>> automatic code generation for overloaded functions in WebKit DOES
>> raise TypeError when it fails to determine which overloaded variant to
>> call.
>> We definitely need to do the strict type checking for WebGL functions.
>>  However, changing the default behavior of the IDL code generators
>> might have a significant compatibility impact. It isn't clear to us
>> whether the current behavior is intentional.  If yes, please let us
>> know and we will try to fix the WebGL part only.  Otherwise we will
>> modify the general rule instead.
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