1049788 - Support [Pref] on a mixin to mean "[Pref] on all the members of this mixin"

Status: REOPENED

(Core :: DOM: Bindings (WebIDL), enhancement, P5)

Description

[Dana Keeler (she/her) (use needinfo) [:keeler] (on leave)]

See bug 1036546. What we would like to have done is this:

(in dom/webidl/Crypto.webidl)

#ifndef MOZ_DISABLE_CRYPTOLEGACY
[NoInterfaceObject,Pref="dom.unsafe_legacy_crypto.enabled"]
interface CryptoLegacy {
  readonly attribute DOMString version;

  attribute boolean enableSmartCardEvents;
...
};

Crypto implements CryptoLegacy;
#endif // !MOZ_DISABLE_CRYPTOLEGACY

That didn't seem to work (when the pref was false, the attributes/functions were still present on window.crypto). Instead, this worked:

#ifndef MOZ_DISABLE_CRYPTOLEGACY
[NoInterfaceObject]
interface CryptoLegacy {
  [Pref="dom.unsafe_legacy_crypto.enabled"
  readonly attribute DOMString version;

  [Pref="dom.unsafe_legacy_crypto.enabled"
  attribute boolean enableSmartCardEvents;
...
};

Crypto implements CryptoLegacy;
#endif // !MOZ_DISABLE_CRYPTOLEGACY

i.e. the pref had to be put on every attribute/function in CryptoLegacy, which is unfortunate.

Comment 1

[Boris Zbarsky [:bzbarsky]]

> [NoInterfaceObject,Pref="dom.unsafe_legacy_crypto.enabled"]

That's pretty much nonsensical.  The Pref annotation on an interface controls visibility of the interface object in global scope (and this is clearly documented, last I checked), but in this case you're saying there is no interface object at all.  Arguably, we should fail codegen on this construct.

If you want to control the visibility of properties with a pref, you need to set [Pref] on those properties.

Comment 2

[Boris Zbarsky [:bzbarsky]]

Ah, bug 921453 covers the codegen issue.

Comment 3

[Boris Zbarsky [:bzbarsky]]

And in particular, there are cases in which we want to hide the interface object but still have the interface properties available (e.g. Console), so we don't want to just blindly propagate conditions from the interface to properties.

Comment 4

[Olli Pettay [:smaug][[e-mail]]]

It is very suboptimal if one needs to Pref all the properties on an [NoInterface] interface.

Comment 5

[Olli Pettay [:smaug][[e-mail]]]

Another solution could be to support Pref with 'implements'.

Comment 6

[Boris Zbarsky [:bzbarsky]]

> Another solution could be to support Pref with 'implements'.

You can "implements" things that have interface objects, so it doesn't work to do that.

If we had explicit mixin syntax, then it would make sense to have [Pref] on a mixin propagate to all its members, just like [Exposed] behaves on a partial interface.  But we don't have that yet (though it's been suggested).

We _could_ have [Pref] on a partial interface propagate to members now, of course.

Comment 7

[Firefox Bug Husbandry Bot]

https://bugzilla.mozilla.org/show_bug.cgi?id=1472046

Move all DOM bugs that haven’t been updated in more than 3 years and has no one currently assigned to P5.

If you have questions, please contact :mdaly.