edition suggestion UI tests fail when CARGO is set

[Noratrieb]

⚠️ for understanding this issue, you can ignore my messages here. they may be seen as funny though ⚠️

failures:
    [ui] tests/ui/async-await/suggest-switching-edition-on-await.rs
    [ui] tests/ui/editions/async-block-2015.rs

(this is the wrong way around, i had it blessed already)
error: /home/nils/projects/rust/tests/ui/async-await/suggest-switching-edition-on-await.rs:9: unexpected help message: '9:7: 9:12: set `edition = "2021"` in `Cargo.toml`'

error: /home/nils/projects/rust/tests/ui/async-await/suggest-switching-edition-on-await.rs:22: unexpected help message: '22:7: 22:12: set `edition = "2021"` in `Cargo.toml`'

error: /home/nils/projects/rust/tests/ui/async-await/suggest-switching-edition-on-await.rs:32: unexpected help message: '32:7: 32:12: set `edition = "2021"` in `Cargo.toml`'

error: /home/nils/projects/rust/tests/ui/async-await/suggest-switching-edition-on-await.rs:41: unexpected help message: '41:7: 41:12: set `edition = "2021"` in `Cargo.toml`'

error: /home/nils/projects/rust/tests/ui/async-await/suggest-switching-edition-on-await.rs:9: expected help message not found: pass `--edition 2021` to `rustc`

error: /home/nils/projects/rust/tests/ui/async-await/suggest-switching-edition-on-await.rs:22: expected help message not found: pass `--edition 2021` to `rustc`

error: /home/nils/projects/rust/tests/ui/async-await/suggest-switching-edition-on-await.rs:32: expected help message not found: pass `--edition 2021` to `rustc`

error: /home/nils/projects/rust/tests/ui/async-await/suggest-switching-edition-on-await.rs:41: expected help message not found: pass `--edition 2021` to `rustc`

[Noratrieb]

hm, this might be entangled with the cursed way i set up https://github.com/gankra/cargo-mommy with my x

[Noratrieb]

hm, even ./x.py directly fails, so mommy is probably innocent~

[Noratrieb]

So, rustc checks whether CARGO is defined. The checked-in test results assume that CARGO is set. But somehow it's not set when I execute compiletest, since I get the generic flag suggestions.

[Noratrieb]

actually it probably is related to my cargo-mommy shenanigans, I set CARGO=path/to/bin/xin my x alias to make cargo-mommy pick up x. This does work for builds, but something seems to confuse test execution.

[Noratrieb]

while the compiletest diff tried to tell me that its not set while it should be, the "unexpected errors" bit tells me that the env var is set while it shouldn't be.

[Noratrieb]

I tried running tests in a fresh checkout free of any shenanigans and that worked fine, so this is a me issue. and no, what seems to be happening is that the var ISN'T set for me, I manually checked the stderr dump from compiletest and it suggests --edition. I also inserted a panic when it is set, and that panic is not triggering.

[Noratrieb]

In both my not working run and the working run, CARGO is not set inside main of compiletest.

[Noratrieb]

and in both runs, CARGO is not set in the Debug output of the rustc Command.. ???

[Noratrieb]

Okay, I resolved most of my confusion, leaving sane behavior that can be debugged:

• turns out I blessed these tests into wrongness before seeing what's wrong, so all results were the wrong way around and confusing
• compiletest does caching slightly differently than I imagined it would do caching

Now I'm left with the sane behavior of ./x works and x doesn't (so my CARGO= in the alias is causing the problem) which I think I can figure out.

[Noratrieb]

Or rather, there is nothing to debug anymore. CARGO is set, which changes the rustc diagnostic. It's as simple as that.