1469712 - ./mach build-backend --dry-run changes mtime of backend file

Status: RESOLVED FIXED

(Firefox Build System :: General, enhancement)

Description

[Michael Shal [:mshal]]

If you change a moz.build file, then './mach build-backend --dry-run --diff' to see what changed in the backend, a future './mach build' will not update the backend. Eg:

./mach build
# Change some moz.build file
./mach build-backend --dry-run --diff
./mach build

The last command should automatically update the backend and build with the new configuration, but the --dry-run command before it is updating the mtime of the backend.FooBackend file so it appears up to date.

Comment 1

[Michael Shal [:mshal]]

Attachment: Bug 1469712 - Don't update mtime for backend file during --dry-run;

When we do a './mach build-backend --dry-run', no files in the objdir
should be written or touched. Updating the mtime of the backend file
during dry-run causes a future './mach build' to think that the backend
is up-to-date when it is not, which causes an incorrect build.

Review commit: https://reviewboard.mozilla.org/r/251676/diff/#index_header
See other reviews: https://reviewboard.mozilla.org/r/251676/

Comment 2

[Chris Manchester (limited bugmail, email directly)]

Comment on attachment 8986308 [details]
Bug 1469712 - Don't update mtime for backend file during --dry-run;

https://reviewboard.mozilla.org/r/251676/#review258058

::: python/mozbuild/mozbuild/backend/base.py:177
(Diff revision 1)
> -            # Always update its mtime.
> +            # Always update its mtime if we're not in dry-run mode.
> +            if not self.dry_run:
> -            with open(list_file, 'a'):
> +                with open(list_file, 'a'):
> -                os.utime(list_file, None)
> +                    os.utime(list_file, None)

It's not entirely clear to me why we need to bump the mtime here, but this change certainly makes sense.

Comment 3

[Gregory Szorc [:gps]]

Comment on attachment 8986308 [details]
Bug 1469712 - Don't update mtime for backend file during --dry-run;

https://reviewboard.mozilla.org/r/251676/#review258060

Comment 4

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/4f001c506ff8
Don't update mtime for backend file during --dry-run; r=gps

Comment 5

[Sebastian Hengst [:aryx] (needinfo me if it's about an intermittent or backout)]

https://hg.mozilla.org/mozilla-central/rev/4f001c506ff8