[Bug 25923] isTypeSupported should be asynchronous

https://www.w3.org/Bugs/Public/show_bug.cgi?id=25923

--- Comment #40 from Boris Zbarsky <bzbarsky@mit.edu> ---
I have one nit about the text.

>         1. If the member's name is unrecognized or unhandled 

Then the implementation won't see it.  Dictionaries in Web IDL work by taking
arbitrary objects and snapshotting the values of the properties the dictionary
cares about.  Other properties are ignored, because they have nothing to do
with the dictionary.

What this means is that if you pass some non-standard value in this dictionary
to an implementation that follows the standard, it will just ignore it.

Apart from that I like this in terms of implementation: this puts the
information about what's being requested up front so the implementation can
figure out how best to communicate that to the user.

Using a sequence here is absolutely correct.  You shouldn't use IDL arrays for
anything; they're on the chopping block to be removed altogether.  But for
reference, since the mail asked, the reason that IDL array of
sequence/dictionary is not allowed is that sequence/dictionary are
pass-by-value, so converting them to/from JS values always makes a copy.  So if
you had an IDL array of them, every read out of the IDL array would create a
new object.  That would be surprising, to say the least.

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Received on Saturday, 4 October 2014 02:14:59 UTC