work around RAs RUSTC_WRAPPER hack

[RalfJung]

Works around rust-lang/rust-analyzer#12973 by un-doing parts of what #157 intended to do, but only #249 actually did: honoring RUSTC_WRAPPER.

@jonhoo are you aware of any cases where ignoring RUSTC_WRAPPER actually causes problems? Seeing as autocfg ignores RUSTC_WRAPPER, it seems unlikely to me.

[RalfJung]

Note that this matches the behavior before #249, because anyhow used to check the wrong env var for this. 1.0.60 is the only version of anyhow that ever respected RUSTC_WRAPPER.

[jonhoo]

I don't actually know of a use of RUSTC_WRAPPER, so can't really add much info. I've heard of it being used to always append certain rustc flags no matter which source is used for the rustc flags that Cargo decides to use, but don't have a concrete example I can link to.

[dtolnay]

I would prefer to ignore only rust-analyzer's buggy RUSTC_WRAPPER specifically. Does it have some kind of recognizable name we could look for?

[RalfJung]

I would prefer to ignore only rust-analyzer's buggy RUSTC_WRAPPER specifically. Does it have some kind of recognizable name we could look for?

I'll have to forward that question to @lnicola

[lnicola]

Does it have some kind of recognizable name we could look for?

RA sets itself as the wrapper, so it should be called rust-analyzer or rust-analyzer.exe. However,

• a tool based on RA might use the same approach
• as mentioned in the issue, IntelliJ Rust takes the same approach (which is where we stole it from from)

[RalfJung]

This should help for RA, not sure if we want to start carrying a list of all the broken wrappers out there...

[jonhoo]

I've found one use of RUSTC_WRAPPER in an internal code-base, and it's used to append to $PATH before delegating to the real rustc. And I'm not even sure that particular use is needed any more. That said, it does feel unfortunate to ignore RUSTC_WRAPPER entirely — even though I don't need it, chances are that if someone does set it it makes a difference to their use-case.

[RalfJung]

OTOH, given that autocfg is widely used and cuviper/autocfg#26 has seen very little activity, it doesn't seem to be terribly common for RUSTC_WRAPPER to be used in a way that just ignoring it causes a lot of trouble.

[dtolnay]

I put up a different workaround in #252 since I think I would prefer not to sweep this under the rug yet as done by this PR.

I would be open to the workaround from this PR only if rust-lang/rust-analyzer#12973 is accepted as a rust-analyzer defect and we see progress toward resolving it, or if someone makes a compelling case that rust-lang/rust-analyzer#12973 is not a rust-analyzer defect and rust-analyzer will therefore not change behavior. The thing I don't want is for this workaround to land and then no follow-up ever occurs about the root cause.

[RalfJung]

Sure, that also works. I locally disabled the rustc-wrapper hack anyway, just posted this because I felt bad for my previous PR triggering that problem.