False positive on context usage within Cleanup funcs

[pkwarren]

According to the docs:

Context returns a context that is canceled just before Cleanup-registered functions are called.

Verified with a small test:

func TestCleanup(t *testing.T) {
	t.Cleanup(func() {
		t.Log(t.Context().Err())
	})
}

This prints context canceled.

It would be nice if the linter would not report issues when contexts are created within Cleanup functions.

Thanks for the linter though - very handy on Go 1.24!

[pkwarren]

For now, I've updated cleanup functions to use context.WithoutCancel(t.Context()) which keeps the linter happy and also doesn't break cleanup.

[ldez]

I don't know if technically I can skip this case because it can be written differently:

func TestCleanup(t *testing.T) {
	ctx := context.Background()
	t.Cleanup(func() {
		t.Log(ctx.Err())
	})
}

The linter detects context.Background() and not the usage of ctx.
Even if I detect context.Background() inside the Cleanup, the problem will remain.

🤔

[sanjayts-dv]

@ldez thank you for this plugin! I would like to add another data point -- @pkwarren 's solution doesn't really work when we want to create a context with deadline when performing cleanup. Right now, we have added //nolint:usetesting directives to the code paths impacted but it is turning out to be messy given we have quite a few testcontainers-go tests.

I do agree with @darren-west from the linked thread that the partial solution would mitigate a lot of common cases. Plus the problematic code sample you have highlighted above can be easily remedied by pulling in the context.Background().

[brasic]

@ldez, I opened #9 with one possible way to fix this, let me know if you have any suggestions.

edit: whoops, didn't realize that #5 already existed to fix this and looks relatively similar, feel free to disregard.

[wreulicke]

@ldez

I don't know if technically I can skip this case because it can be written differently:
The linter detects context.Background() and not the usage of ctx.
Even if I detect context.Background() inside the Cleanup, the problem will remain.

I think t.Context() should not be used inside the Cleanup. (the context is cancelled inside the cleanup)
There is a difference between disallowing context.Background() and that.
So, then, #5 meets my consideration.
I think we need to detect t.Context() inside the Cleanup as the problem.
But, that conflicts current linter implementation. So we need #5 I think.