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[Bug 25347] New: [MSE] 'nullable' arguments and type conversions and INVALID_ACCESS_ERR (vs. WebIDL)

From: <bugzilla@jessica.w3.org>
Date: Tue, 15 Apr 2014 11:56:17 +0000
To: public-html-media@w3.org
Message-ID: <bug-25347-5436@http.www.w3.org/Bugs/Public/>
https://www.w3.org/Bugs/Public/show_bug.cgi?id=25347

            Bug ID: 25347
           Summary: [MSE] 'nullable' arguments and type conversions and
                    INVALID_ACCESS_ERR (vs. WebIDL)
           Product: HTML WG
           Version: unspecified
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: Media Source Extensions
          Assignee: adrianba@microsoft.com
          Reporter: fs@opera.com
        QA Contact: public-html-bugzilla@w3.org
                CC: mike@w3.org, public-html-media@w3.org

Throughout this specification method arguments are marked as non-nullable
(consistently in both the parameter table and the IDL-fragments), but the
'null' value is still assumed handled in the algorithm steps.

Example:

interface MediaSource : EventTarget {
    ...
    SourceBuffer   addSourceBuffer (DOMString type);
    void           removeSourceBuffer (SourceBuffer sourceBuffer);
    ...
};

"addSourceBuffer
...
When this method is invoked, the user agent must run the following steps:

1. If type is null or an empty string then throw an INVALID_ACCESS_ERR
exception and abort these steps.
...
removeSourceBuffer
...
When this method is invoked, the user agent must run the following steps:

1. If sourceBuffer is null then throw an INVALID_ACCESS_ERR exception and abort
these steps."

In both of these cases the algorithmic steps assumes null is a valid value and
handles it.
However, assuming WebIDL semantics [1], these methods would never be invoked
with null as the value. In the case of addSourceBuffer(null), null would be
converted to the string 'null' [2], and for removeSourceBuffer(null) a
TypeError exception would be thrown because the null value cannot be converted
to an object of interface type "SourceBuffer" [3].

Similar issues exists for other methods in the specification.

[1] The spec does not reference WebIDL AFAICS, but seems to follow notational
and other conventions from it.
[2] http://heycam.github.io/webidl/#es-DOMString
[3] http://heycam.github.io/webidl/#es-interface

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Received on Tuesday, 15 April 2014 11:56:19 UTC

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