rustdoc: Support argument files

[ojeda]

Factors out the rustc_driver logic that handles argument files so that rustdoc supports them as well, e.g.:

rustdoc @argfile

This is needed to be able to generate docs for projects that already use argument files when compiling them, e.g. projects that pass a huge number of --cfg arguments.

The feature was stabilized for rustc in #66172.

[ojeda]

It seems rustbot didn't notice.

r? @jyn514

[ojeda]

I assume I can't assign an S* label, but let's try.

@rustbot label: +T-rustdoc, +S-waiting-on-review

[jyn514]

Looks great, thanks! I left some nits about the tests, but I don't feel super strongly about any of them.

[ojeda]

Thanks!

Note that I copied the test files from rustc unmodified. So it depends whether you prefer to keep them in sync or tailor them better for rustdoc :)

[jyn514]

Ok, if you can just change build-pass to check-pass that would be enough I think :) build-pass isn't really meaningful for rustdoc.

[ojeda]

Ah, in case you take a look at how the code looks for rustc on usage():

rust/compiler/rustc_driver/src/lib.rs

Lines 824 to 830 in 0148b97

	let at_path = if verbose && nightly_build {
	" @path Read newline separated options from `path`\n"
	} else {
	""
	};
	println!(
	"{options}{at_path}\nAdditional help:

The nightly_build is a mistake since it is already stable (I sent #82260 to fix that one); and verbose isn't present in rustdoc so far so I felt I shouldn't introduce it just for that (let me know if you prefer we do that).

[jyn514]

verbose isn't present in rustdoc so far so I felt I shouldn't introduce it just for that (let me know if you prefer we do that).

Nah, this seems fine :) thanks!

@bors r+

[bors]

📌 Commit 755b3fc has been approved by jyn514

[ojeda]

You're welcome!

Also, #66172 was tagged as relnotes, so you might to tag this one too.