264729 - Ease debugging with support for error events

Status: RESOLVED WONTFIX

(Core :: XBL, enhancement)

Description

[Nigel McFarlane]

It would ease the debugging process for app development if
XBL bindings that failed to attach generated a
DOM 3 Events HTML "error" event (section 1.5.5, DOM 3 Events).
That is the general intent of the "error" event.

I'm not sure if this enhancement request belongs under the
XBL, HTML, XML, XHTML, SVG or XUL component, since it can be
applied to most of them.

Example of when such an event might be useful:

- if the binding fails to be retrieved when specified.

- if the binding attach point is specified correctly
  but the binding fails to parse when first parsed.

- if the binding attach point is specified correctly
  but the binding has nonsensical semantics.

- if a binding contains a script that fails to parse.

- if a script in the binding performs synchronous
  initialisation and throws an error when that fails.

- if subsidiary bindings or other resources fail to
  be retrived by any overarching bindings.

- in a GUI building tool that attempts to dynamically
  attach a hand-written binding.

In general, on the first pass through an error event
would be useful in all uses of -moz-binding.

If the binding is mutated for any reason subsequent to
attachment, then perhaps a further error event is too
severe a consequence. For a first pass, though, it is
valuable information.

Comment 1

[Nickolay_Ponomarev]

My understanding is that XBL2 defines specific rules for error processing, which are basically ignore the erroneous declaration and report it to the user (for example via the Error Console). It doesn't require the error event to be fired.

Comment 2

[Boris Zbarsky [:bzbarsky]]

XBL is now disabled in Firefox (Bug 1583314) and is in the process of being removed from Gecko (Bug 1566221), so closing bugs requesting changes to its implementation as wontfix.