Make functional tests depend on nix binary so they auto recompile

[fzakaria]

Trivial improvement to Meson.
I noticed plenty of tests don't depend on nix itself which is frustrating since I forget to do meson compile.

Slowly making the build graph more "correct".
I'm not an expert in Meson so not sure if this is ultimately correct but it does what I expect.

---

Add 👍 to pull requests you find important.

The Nix maintainer team uses a GitHub project board to schedule and track reviews.

[fzakaria]

@xokdvium ask and you shall receive.

[fzakaria]

This works for me locally... not sure about this nix build why it's complaining.
I'm trying to see what the "correct" approach is with declare_dependency or what not.

[fzakaria]

The meson setup is pretty convoluted.
Maybe @Ericson2314 can recommend the "right way".

Folks on #mesonbuild didn't give me much in the way of advice.

[Ericson2314]

It's supposed to already do this with the existing "find program", IIRC. If it's not working, a bug should be submitted to Meson.

[Ericson2314]

You also don't want to change the main suite, you want to change the loop at the bottom to include nix in addition to the suite-specific deps.

[fzakaria]

It does not work for me @Ericson2314 -- just change any source line and run meson test -C build fetchGit for instance.
Can you confirm you see the same issue?

I couldn't find documentation claiming that findProgram should be causing rebuilds properly. If so, I can open up a ticket with our project as a reproducer.

[Ericson2314]

@fzakaria so to be clear, my first comment is maybe not quite right, I think the find_program return value should cause proper rebuilds, but only if it is used. If we do

diff --git a/tests/functional/meson.build b/tests/functional/meson.build
index 8f2b1ff59a..4a7dfae5d5 100644
--- a/tests/functional/meson.build
+++ b/tests/functional/meson.build
@@ -249,7 +249,7 @@ foreach suite : suites
       # them more time than the default of 30 seconds.
       timeout : 300,
       # Used for target dependency/ordering tracking, not adding compiler flags or anything.
-      depends : suite['deps'],
+      depends : [nix] + suite['deps'],
       workdir : workdir,
     )
   endforeach

(what my second comment proposes), then it should work. If it still doesn't work, then I think that is a Meson bug.

[fzakaria]

@Ericson2314 the build was failing with depends having nix because of the type:

ERROR: test keyword argument 'depends' was of type array[ExternalProgram]
but should have been array[BuildTarget | CustomTarget | CustomTargetIndex]

[Ericson2314]

ah ok @fzakaria. Then yes it might be a feature request, but it should still be a Meson issue:

1. When the program is truly external, this should just be ignored. Truly external things don't change by definition.
2. When the program is overridden with an internal program, it should just work via the underlying target.

[Ericson2314]

I'll just open the issue :)

[Ericson2314]

mesonbuild/meson#14874 OK there is the issue

[xokdvium]

@fzakaria, @Ericson2314 this should now work perfectly locally as well as in CI. Also needed some fixes for perl dependency tracking.