1745963 - Running Firefox from `./mach run` forces Fission to be disabled

Status: RESOLVED FIXED

(Firefox Build System :: General, defect, P2)

Description

[Mike Conley (:mconley) (:⚙️)]

STR:

1. Create a new local build of Firefox
2. Run it with ./mach run
3. Open the Browser Console, and type in: Services.appinfo.fissionAutostart and press enter

ER:

It should return true.

AR:

It returns false.

It seems that when we launch Firefox from ./mach run, Fission is being force-disabled. It can be re-enabled with ./mach run --enable-fission, but that seems non-obvious and probably the wrong default.

I suspect this is a regression from 1732358.

Comment 1

[Mike Conley (:mconley) (:⚙️)]

Hey ahal, is there some mach stuff needed to make Fission-enabled be the default state for local builds?

Comment 2

[Dave Townsend [:mossop]]

We should probably replace the --enable-fission with --disable-fission

Comment 3

[Andrew Halberstadt [:ahal]]

For test harnesses this is being tracked in bug 1744091. I'll admit mach run wasn't on my radar, it's probably more of an Engineering Workflow item.. but maybe we can fix this one at the same time?

Comment 4

[Nika Layzell [:nika] (ni? for response)]

This should be as simple as flipping around the argument and then the check here: https://hg.mozilla.org/mozilla-central/file/6a8175e7c32b19d28ab4fa35b3eb385418234b20/python/mozbuild/mozbuild/mach_commands.py#l1781. Unfortunately the arguments are shared between desktop and android, which still has fission disabled, so we may need to instead add a second enable_fission argument and then flip the prefs based on which is passed, setting MOZ_FORCE_DISABLE_FISSION to disable, and MOZ_FORCE_ENABLE_FISSION to enable (or nothing if no flag is passed)

Comment 5

[BugBot [:suhaib / :marco/ :calixte]]

Set release status flags based on info from the regressing bug 1732358

Comment 6

[Jens Stutte [:jstutte]]

Rating could be even S4 from users perspective, but it is a possible source of confusion for developers, thus the P2/S3.

Comment 7

[Geoff Brown [:gbrown] (pto Apr 11-18)]

This should be working now: 'mach run' (desktop) runs firefox with fission enabled; use --fission-disable to disable.