STR:

1. mozillabuild 4.0
2. vim 8.2 for windows from the developers' website (ensure it's on $PATH before mozillabuild stuff)
3. vimrc set to set fileformats=unix,dos (in case that matters)
4. open any mozilla-central file from a mozillabuild shell, using gvim path/to/file from the root of the repo
5. in vim run :! hg diff %

ER:
you get a diff in a console window

AR:

C:\mozilla-build\msys2\usr\bin\bash.exe -c "hg diff tools/moztreedocs/mach_commands.py"
/usr/bin/bash: /c/mozilla-build/python3/Scripts/hg: c:\mozillabuild-stage\mozilla-build\python3\python.exe^M: bad interpreter: No such file or directory
shell returned 126
Hit any key to close this window...

I don't really know what specifically is breaking this; the weird windows line ends (the ^M) or the non-existent strange mozillabuild-stage path (what is that?), or the mixed use of forward and backward slashes could all be at fault.

I don't know what else this effects, and if e.g. the issue is limited to hg commands and/or use from vim, or is more widespread. hg use direct from the mozillabuild commandline seems fine.

Interesting, can you try the workaround described in this related bug?

(In reply to Mitchell Hentges [:mhentges] 🦀 from comment #1)

Interesting, can you try the workaround described in this related bug?

Apologies for the slow response, I went on PTO.

The workaround doesn't seem to fix things, though it changes the error message - I now just get "shell returned 255" .

I'll also note that after applying that workaround (also from gvim...), gvim hiccups:

"/mozilla-build/python3/Scripts/hg" [unix] 61L, 1812B written
syntastic: error: checker output:
Traceback (most recent call last):
  File "C:\Users\[something]\vimfiles\bundle\syntastic\syntax_checkers\python\compile.py", line 11, in <module>
    compile(open(argv[1]).read(), argv[1], 'exec', 0, 1)
FileNotFoundError: [Errno 2] No such file or directory: 'C:/mozilla-build/msys2/mozilla-build/python3/Scripts/hg'

in case that's helpful...

Hey, I hope your PTO was good :)
Can you try the MozillaBuild 4.0.1 release, just to see if its upstream "shebang fix" improves your situation?

This path (C:/mozilla-build/msys2/mozilla-build/python3/Scripts/hg) is definitely weird, either way.

(In reply to Mitchell Hentges [:mhentges] 🦀 from comment #3)

Hey, I hope your PTO was good :)
Can you try the MozillaBuild 4.0.1 release, just to see if its upstream "shebang fix" improves your situation?

Unfortunately that didn't improve things:

C:\mozilla-build\msys2\usr\bin\bash.exe -c " hg diff"
shell returned 255
Hit any key to close this window...

The severity field is not set for this bug.
:andi, could you have a look please?

For more information, please visit auto_nag documentation.

The severity field is not set for this bug.
:ahochheiden, could you have a look please?

For more information, please visit auto_nag documentation.