1656863 - `Uncaught (in promise) Error: not allowed` on about:compat

Status: RESOLVED FIXED

(Web Compatibility :: Interventions, defect, P1)

Description

[Dennis Schubert [:denschub]]

In the current nightly, about:compat is empty, showing an exception in the JS console

Uncaught (in promise) Error: not allowed
    <anonymous> moz-extension://cd379ded-2d01-a345-ae77-e2bc31021b43/about-compat/aboutCompat.js:49

Comment 1

[Dennis Schubert [:denschub]]

This appears to be a regression of bug 1637329! Note that, for some reason, it works fine if you have about:compat loaded at the start (for example by using -a "about:compat" in mozregression, but not if you open a new tab and access the page.

Tom, does something come to mind here?

Comment 2

[Thomas Wisniewski [:twisniewski]]

No, I'm not sure why that promise would suddenly be failing. But I will have a look tomorrow.

Comment 3

[Thomas Wisniewski [:twisniewski]]

Ah, it turns out that this happens because both the shims and about:compat broker both use browser.runtime.onMessage, and only one of them ends up being called due to both possibly returning a value. The fix isn't too involved - just making sure that both handlers get a chance to process the message, even if one of them returns undefined when it tries to ignore a given message.

Comment 4

[Thomas Wisniewski [:twisniewski]]

Attachment: Bug 1656863 - ensure that about:compat and shims both get a chance to process messages; r?denschub

Comment 5

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/bb010698831c
ensure that about:compat and shims both get a chance to process messages; r=denschub,webcompat-reviewers

Comment 6

[Cristian Brindusan [:cbrindusan]]

https://hg.mozilla.org/mozilla-central/rev/bb010698831c