[webkit-dev] Optional parameter in IDL and undefined JS value

[Jian Li]

This seems not to work. When we call foo(arg1, undefined), arguments.length
is 2 and thus we convert undefined to 0 and pass it to impl->foo(arg1,
arg2). But we want default value for arg2 other than 0.

On Fri, Apr 22, 2011 at 8:52 AM, Oliver Hunt <oliver at apple.com> wrote:

> An alternative would be to generate code for optional args along the lines
> of (pseudo code):
> void foo(Arg1Type arg1, [Optional] Arg2Type arg2);
> =>
> Arg1Type arg1 = toArg1Type(arguments[0]);
> if (arguments.length < 2)
>     return impl->foo(arg1);
> Arg2Type arg2 = toArg2Type(arguments[1]);
> return impl->foo(arg1, arg2);
>
>
> This would allow the C++ impl to use overloading to resolve things
> correctly.
>
> --Oliver
>
> On Apr 21, 2011, at 10:16 PM, Jian Li wrote:
>
> One other way is to write custom binding code to handle this
> case specially.
>
>
> On Thu, Apr 21, 2011 at 10:07 PM, Maciej Stachowiak <mjs at apple.com> wrote:
>
>>
>> On Apr 21, 2011, at 6:29 PM, Jian Li wrote:
>>
>>  I've pinged the spec author to make it clear in the spec. What is meant
>> in the spec is really that we want Blob.slice to have the same exact
>> behavior as Array.slice defined in ECMAScript 5, 15.4.4.10. That is,
>> Blob.slice(start) has the same result as Blob.slice(start, undefined).
>>
>> The current code generator scripts will convert undefined value to 0. But
>> we really want to use the custom default value for Blob.slice. Do we want to
>> consider adding "DefaultValue=" extended attribute support to IDL?
>>
>>
>> I'd prefer if we can find a way to solve it that does not require
>> diverging our IDL dialect further from Web IDL, especially since this is the
>> only method likely to need the feature. Are there any other practical
>> solutions?
>>
>> Regards,
>> Maciej
>>
>>
>> Thanks,
>>
>> Jian
>>
>>
>> On Thu, Apr 21, 2011 at 3:38 AM, Maciej Stachowiak <mjs at apple.com> wrote:
>>
>>>
>>> On Apr 21, 2011, at 12:14 AM, Jian Li wrote:
>>>
>>> > The current File API spec says that:
>>> >     If the end parameter is not provided (undefined), let relativeEnd
>>> be size.
>>>
>>> That seems like loose wording. Parameter not provided and parameter
>>> provided with a value of undefined are in general not the same thing. The
>>> spec should be explicit about which cases it's talking about.
>>>
>>> Regards,
>>> Maciej
>>>
>>
>>
>>
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