Tracking Issue for -Z crate-attr

[jyn514]

This is a tracking issue for the -Z crate-attr unstable option.

About tracking issues

Tracking issues are used to record the overall progress of implementation.
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A tracking issue is however not meant for large scale discussion, questions, or bug reports about a feature.
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Steps

• Adjust documentation (see instructions on rustc-dev-guide)
• Stabilization PR (see instructions on rustc-dev-guide)

Unresolved Questions

• this likely needs an RFC, since it landed without much discussion? i am tentatively planning to do this at the same time as an RFC for #![register_tool].
• probably we will want to limit the syntax? for example, -Z crate-attr='crate_name= /* foo */ "test"' is currently accepted without warning, and -Z crate-attr='crate_name=/*' gives an error about an unterminated block comment.
• fix interactions with doctests: rustdoc --test does not respect -Zcrate-attr #138491
• we should improve diagnostics; currently we treat the attribute as surrounded by #![ /*...*/ ], but don't show the surrounding code in the error:

; rustc src/main.rs -Z crate-attr='#![crate_name="test"]'
error: expected identifier, found `#`
 --> <crate attribute>:1:1
  |
1 | #![crate_name="test"]
  | ^ expected identifier

Implementation history

• Initial implementation: Add the -Zcrate-attr=foo unstable rustc option #52355
• Recommended in other diagnostics: fix #113702 emit a proper diagnostic message for unstable lints passed from CLI #114959
• Documentation and tests: Document -Z crate-attr #138288
• Improve diagnostics for crate-attr itself: Improve -Z crate-attr diagnostics #138336

[jyn514]

some places where this has been mentioned as useful:

• doc(html_no_source): Add an option to exclude source code from docs #75497
• enabling unstable lints: Unstable lints passed on command line can only be ungated from source code #113702
• test frameworks: Add the -Zcrate-attr=foo unstable rustc option #52355 (comment)
• i think this could be useful for register_tool: Tracking issue for #![register_tool] #66079 (comment)
• in general, we have a bunch of attributes that are duplicated as flags (-A/W/D/F, --crate-name, --crate-type). -Z crate-attr allows us not to have to decide between an attribute, flag, or both, because adding an attribute automatically allows it to be specified as a flag.

[fmease]

we have a bunch of attributes that are duplicated as flags

--edition

Not edition, there's no #![edition = …] (but it used to exist a long time ago for a brief period iirc)