unstable proc_macro tracked::* rename/restructure

[drahnr]

Extracted restructure of the unstable tracked::{fs,env}::*

Originally part of #84029

It's slightly clunky to to have three distinct unstable features, since one cannot use two annotations on one mod tracked {..} declaration.

The second thing I am unsure is rust-analyzer which would need some adaption for the new structure.

CC @Xanewok

[rust-highfive]

r? @petrochenkov

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[petrochenkov]

I'm going to transfer this to the libs API team.
These are APIs that allow to trigger a rebuild when a certain environment variable or a file used from a proc macro change.

I'm not sure what the current library conventions are, but seeing >2 segment paths like tracked::fs::path in code is uncommon, so the new structure will likely result in the API being used through renamed imports like

use tracked::fs::path as track_path;use tracked::env::var as tracked_env_var;fnmy_proc_macro(){track_path("my_file.txt");// returns nothinglet var = tracked_env_var("MY_VAR");// returns the variable's value}

[drahnr]

Totally understandable, and I don't have a strong opinion, mostly going off of what was discussed in the referenced #84029 issue. If it is at odds with the current naming and module nesting depth, feel free to close.

At the very least though, I think it should be unified to either track_ or tracked_ prefixes for consistency.

[joshtriplett]

We discussed this in today's @rust-lang/libs-api meeting. We don't want to see an extra level of submodule nesting here; we should just have tracked::path and tracked::env_var. We didn't find the parallel with std compelling, because this will never have any significant fraction of std, and of the two methods we already have, one (path) already has no parallel in std.

Also, separate from this issue, several people in the meeting felt that we shouldn't restrict path to just str. We understand that the metadata format currently can't handle non-UTF-8, but we'd still like to see this accept a path, to avoid hardcoding that limitation in the API. We can always internally raise an error if it's not UTF-8 and the metadata can't handle it.

[drahnr]

@m-ou-se I'll implement the required changes this week, just wasn't entirely sure what your self assignment implied.

[pksunkara]

so the new structure will likely result in the API being used through renamed imports like

Shouldn't we name the functions track_path and track_env_var then?

[drahnr]

so the new structure will likely result in the API being used through renamed imports like

Shouldn't we name the functions track_path and track_env_var then?

I'd prefer the one module level variants, which is in line with other macro impls iirc:

.. we should just have tracked::path and tracked::env_var ..

[drahnr]

Also, separate from this issue, several people in the meeting felt that we shouldn't restrict path to just str. We understand that the metadata format currently can't handle non-UTF-8, but we'd still like to see this accept a path, to avoid hardcoding that limitation in the API. We can always internally raise an error if it's not UTF-8 and the metadata can't handle it.

What's meant by internally raising an error, where should this be handled? Is path.to_str().expect() good enough? Encode does not provide means to return a result type. I'd appreciate some input.

[drahnr]

Pending access to something that can be cast to a byte slice, the impl currently accepts valid UTF-8 only. I am not sure the error handling is as desired. Either way, I'd like some feedback :) Thanks!

@rustbot label -S-waiting-on-author +S-waiting-on-review

[petrochenkov]

It's not necessary to return a Result, proc macro server can simply report a compiler error if the passed Path is non-UTF8.

I'm not sure whether proc macro bridge can support passing Path though.
If it cannot, then we could actually determine non-UTF8-ness on the client side and return a Result.

[drahnr]

It's not necessary to return a Result, proc macro server can simply report a compiler error if the passed Path is non-UTF8.

I'm not sure whether proc macro bridge can support passing Path though.
If it cannot, then we could actually determine non-UTF8-ness on the client side and return a Result.

Technically this would be possible, but that would require to access the currently private fn as_u8_slice and the unsafe fn from_u8_slice to be usable from the encode/decode impl.

I added an implementation adding a Result at the outer level, avoiding the encode and decode impls for PathBuf.

[JohnCSimon]

Ping from triage:
@drahnr - can you please post your status on this PR?

[bors]

☔ The latest upstream changes (presumably #118646) made this pull request unmergeable. Please resolve the merge conflicts.

[rdrpenguin04]

What's left on this?

[drahnr]

What's left on this?

A review, and another rebase, I think. It's been a while.

[m-ou-se]

This PR does a few different things at once. One of them is changing the &str type to a PathBuf. That change was requested here and would be fine to merge. The other changes seem unrelated and it's unclear why some of them were made. (E.g. changing the tracking issue, or changing "environment" to "env" in a comment, or reordering some attributes/doc comments, etc.)

[m-ou-se]

Why is the tracking issue changed? #74690 is a closed issue.

[m-ou-se]

I find the note on windows/unix paths quite confusing. Who is that note for? What user error is it trying to prevent?

[m-ou-se]

Is it not relative to the current working directory? So if I do File::open("a.txt") and tracked_path::path("a.txt"), can that refer to a different file?

[bjorn3]

If I understand the docs correct, this would behave similar to using the include!() family in the macro expansion, which indeed uses a different directory to be relative to than File::open() inside the proc macro. The behavior of include!() is almost certainly what you want. The current working directory that rustc is invoked with when using cargo is effectively undefined.

[alex-semenyuk]

@drahnr
From wg-triage. Could you please take a look comments and make rebase?

[Dylan-DPC]

Closing this as inactive. Feel free to reöpen this pr or create a new pr if you get the time to work on this. Thanks

[Skgland]

Would it be alright to pick up the "uncontroversial" changes from this i.e. restructuring/renaming and changing AsRef to AsRef? That appear to be the next not blocked step to me.