1390170 - DOMException.prototype should have .message and .name

Status: RESOLVED FIXED

(Core :: DOM: Core & HTML, enhancement)

Description

[Aryeh Gregor (:ayg) (no longer with Mozilla)]

Accessing DOMException.prototype.name and DOMException.prototype.message directly throws in Chrome and Edge.  This seems correct per spec, because WebIDL defines them as IDL properties of DOMException, and those do throw if you access them directly:

https://heycam.github.io/webidl/#idl-DOMException

Currently we put them on a nonstandard ExceptionMembers interface that DOMException implements.  It might fix things if we just moved these two properties to DOMException itself.

Comment 1

[Aryeh Gregor (:ayg) (no longer with Mozilla)]

Attachment: Bug 1390170 - DOMException.prototype should have .message and .name

The spec requires that they be interface members:

  https://heycam.github.io/webidl/#idl-DOMException

This means they're on the prototype.  This change brings us in line with
Chrome, Edge, and WebKit, as tested by
<https://github.com/w3c/web-platform-tests/pull/6875>.

Review commit: https://reviewboard.mozilla.org/r/168722/diff/#index_header
See other reviews: https://reviewboard.mozilla.org/r/168722/

Comment 2

[Ben Kelly [:bkelly, not reviewing]]

Comment on attachment 8897407 [details]
Bug 1390170 - DOMException.prototype should have .message and .name

https://reviewboard.mozilla.org/r/168722/#review174026

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/e596de179468
DOMException.prototype should have .message and .name r=bkelly

Comment 4

[Wes Kocher (:KWierso) (Not reading bugmail; email directly if needed)]

https://hg.mozilla.org/mozilla-central/rev/e596de179468

Comment 5

[Boris Zbarsky [:bzbarsky]]

I don't understand this change.  ExceptionMembers is implemented by both DOMException and Exception; all its members are installed on the relevant prototypes.  The shared code was shared so we wouldn't duplicate it.

The throwing vs non-throwing was fixed in bug 1378985.

Why did we introduce the code-duplication here?  I can see some value in having the IDL look more like the spec, I guess, but was there any other reason?

Comment 6

[Ben Kelly [:bkelly, not reviewing]]

(In reply to Boris Zbarsky [:bz] (still digging out from vacation mail) from comment #5)
> I don't understand this change.  ExceptionMembers is implemented by both
> DOMException and Exception; all its members are installed on the relevant
> prototypes.  The shared code was shared so we wouldn't duplicate it.

Ok.  This wasn't obvious to me reading the webidl.  AFAICT ExceptionMembers was labeled as "legacy" and the proposed patch was bringing us into alignment with the webidl in the specs.

> The throwing vs non-throwing was fixed in bug 1378985.
> 
> Why did we introduce the code-duplication here?  I can see some value in
> having the IDL look more like the spec, I guess, but was there any other
> reason?

I don't object to backing it out, but it might be nice to document how ExceptionMembers works in the webidl.