Make rustdoc lints a tool lint instead of built-in

[jyn514]

• Rename broken_intra_doc_links to rustdoc::broken_intra_doc_links (and similar for other rustdoc lints; I don't expect any others to be used frequently, though).
• Ensure that the old lint names still work and give deprecation errors
• Register lints even when running doctests
• Move lint machinery into a separate file
• Add declare_rustdoc_lint! macro

Unblocks #80300, #79816, #80965. Makes the strangeness in #77364 more apparent to the end user (note that missing_docs is not moved to rustdoc in this PR). Closes #78786.

Current status

This is blocked on #82620 (see #80527 (comment))

[rust-highfive]

r? @GuillaumeGomez

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[bors]

💔 Test failed - checks-actions

[JohnTitor]

@bors retry

[lopopolo]

I would have liked to see the rustdoc lint group/tool name exist on stable before this change was merged.

It is not possible to run both nightly and stable builds with -D warnings and warn(broken_intra_doc_links)/warn(rustdoc:: broken_intra_doc_links) now because, despite allow(unknown_lints), the unknown tool name results in a hard error:

error[E0710]: an unknown tool name found in scoped lint: `rustdoc::broken_intra_doc_links`
 --> artichoke-core/src/lib.rs:9:9
  |
9 | #![warn(rustdoc::broken_intra_doc_links)]
  |         ^^^^^^^

[jyn514]

It is not possible to run both nightly and stable builds with -D warnings and warn(broken_intra_doc_links)/warn(rustdoc:: broken_intra_doc_links) now because, despite allow(unknown_lints), the unknown tool name results in a hard error:

If you use the original name (broken_intra_doc_links) and allow(renamed_removed_lints), it should work.

[lopopolo]

@jyn514 does the introduction of a new tool name mean that declaring this lint as a crate level warn pragma will bump the MSRV of the crate?

[lopopolo]

If you use the original name (broken_intra_doc_links) and allow(renamed_removed_lints), it should work.

Since the lint has been removed, does this mean running nightly rustdoc will not detect broken intradoc links anymore?

[jyn514]

Since the lint has been removed, does this mean running nightly rustdoc will not detect broken intradoc links anymore?

No, the lint name will still apply (since #82620).

@jyn514 does the introduction of a new tool name mean that declaring this lint as a crate level warn pragma will bump the MSRV of the crate?

Yes, unfortunately. There's no way to fix this because past releases are immutable (ideally the unknown tool name would only be a warning and not a hard error).

[lopopolo]

Thanks for the context. I think the best path forward for me is to remove the pragmas and add -D rustdoc::broken_intra_doc_links to CI via RUSTDOCFLAGS.

ideally the unknown tool name would only be a warning and not a hard error

Has this change landed in nightly/is there a ticket for it?

[jyn514]

Has this change landed in nightly/is there a ticket for it?

I think #66079 (comment) is the closest issue.

[lopopolo]

Thank you!

[jyn514]

I would have liked to see the rustdoc lint group/tool name exist on stable before this change was merged.

@lopopolo I opened #83203 to turn off the warnings until this makes it to stable.