"Subproject_dir must not contain a path segment" in master breaks projects

[ximion]

Hi!
The new check introduced in c178a57 breaks existing projects which place their subprojects' wrap files in project subdirectories, e.g. contrib/subprojects.
I've seen this quite often and actually used that particular path myself (why create another toplevel directory if there already is a directory dedicated for similar stuff?).

While I agree that paths like ../dummy in there are awful, I think disallowing putting the files in any subdirectory is a bit aggressive. Can the check be relaxed to only check for the "is an absolute path used" and "is a relative path used that goes beyond the source_root" cases, or is there an obvious bug in using a level-2-subdirectory in source_root?

[ximion]

I just now was debugging an issue someone found in the Vibe.d project when compiling it with Meson (see vibe-d/vibe.d#1983 (comment) for reference).
The Vibe.d project uses lib/subprojects/ as its wrapfile directory, and compiles fine with Meson 0.42.x. When upgrading to Meson 0.43.x that apparently broke with the worst possible error message (stating a wrong cause). Upon moving the subprojects dir to the project's toplevel directory, everything started to work again.

So, I guess there is definitely some issue here with using a nested subproject directory, but this issue was only introduced with Meson 0.43 and isn't present in prior versions.

[ximion]

Any news on this one? I would really like to know what the course of action is (I can't even submit a patch without knowing what the Meson maintainers would like to do).
This is also blocking updates to newer Meson versions in a couple of projects, and it's one of the bugs keeping Meson from being updated in Debian testing.

[jpakkane]

I guess we can change the check to ensure that there are no .. segments in the directory name.

[ximion]

That would work for me, and also ensure the subproject dir stays in the project's source tree and not some random location. So, check that subprojects_dir is not an absolute path and contains no .. would definitely resolve this for 99.9% of all people (and the rest should fix their Meson file).