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

Adam Barth abarth at webkit.org
Wed Aug 11 19:13:03 PDT 2010

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.


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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