compiletest: Make `aux-crate` directive explicitly handle `--extern` modifiers #151353

Enselic · 2026-01-19T04:37:54Z

With -Zunstable-options it is possible to pass options to --extern. See here for an exhaustive list of possible options:

rust/compiler/rustc_session/src/config.rs

Lines 2356 to 2367 in b5dd72d

    
           "priv" => is_private_dep = true, 
        
           "noprelude" => { 
        
               if let ExternLocation::ExactPaths(_) = &entry.location { 
        
                   add_prelude = false; 
        
               } else { 
        
                   early_dcx.early_fatal( 
        
                       "the `noprelude` --extern option requires a file path", 
        
                   ); 
        
               } 
        
           } 
        
           "nounused" => nounused_dep = true, 
        
           "force" => force = true,

Using these options works with the aux-crate directive, but only because the options pretend to be part of the name. Make it clearer what aux-crate supports by explicitly handling --extern options.

This PR is step one of splitting up #151258 into smaller pieces.

r? @Zalathar

rustbot · 2026-01-19T04:37:57Z

Some changes occurred in src/tools/compiletest

cc @jieyouxu

Zalathar · 2026-01-19T06:46:53Z

Ah, so we're talking about these?

“Options” seems like a needlessly confusing term to have been used on that unstable-book page; calling them “modifiers” (as the tracking issue does) is a lot clearer.

Zalathar · 2026-01-19T06:51:27Z

src/tools/compiletest/src/directives/auxiliary.rs

+    /// With `aux-crate: noprelude:foo=bar.rs` this will be `noprelude`.
+    pub extern_opts: Option<String>,


I think we should ignore the unstable book and the compiler source, and call these “extern modifiers” instead.

This field comment really needs to give a brief explanation of what extern modifiers actually are, perhaps with a link to the tracking issue.

Tracking Issue --extern crate modifiers #98405

I agree "extern modifiers" is a better name than "extern options". I added some more info and linked to the tracking issue. I don't think we should give too many details though since we don't want that comment to become outdated soon.

I also added references this functionality in the rustc-dev-guide.

Zalathar · 2026-01-19T06:52:37Z

src/tools/compiletest/src/directives/auxiliary.rs

+    let opts_and_name = parts.next().expect("missing aux-crate name (e.g. log=log.rs)").to_string();
+    let path = parts.next().expect("missing aux-crate value (e.g. log=log.rs)").to_string();
+    let (opts, name) = match opts_and_name.split_once(':') {
+        None => (None, opts_and_name),
+        Some((opts, name)) => (Some(opts.to_string()), name.to_string()),
+    };
+    AuxCrate { extern_opts: opts, name, path }


This parsing step is getting complex enough that a regex might be an improvement. Seems worth a try at least.

I tried porting it to a regex but didn't think it ended up being easier to understand, so I kept it as is. I hope that's OK. The diff is small at least.

I spent some more time on it and found a way to use a regex that I like. Hopefully you'll like it too.

Zalathar · 2026-01-19T06:58:15Z

We should also mention --extern modifiers in the dev-guide docs for //@ aux-crate, precisely because they're so obscure that it's difficult for an unfamiliar reader (e.g. me yesterday) to figure out what they even are.

rustbot · 2026-01-19T19:30:12Z

The rustc-dev-guide subtree was changed. If this PR only touches the dev guide consider submitting a PR directly to rust-lang/rustc-dev-guide otherwise thank you for updating the dev guide with your changes.

cc @BoxyUwU, @jieyouxu, @Kobzol, @tshepang

Zalathar · 2026-01-24T03:02:31Z

src/tools/compiletest/src/directives/auxiliary.rs

+    // Matches:
+    //   name=path
+    //   modifiers:name=path
+    let caps = static_regex!(r"^(?:(?P<modifiers>[^=]*?):)?(?P<name>[^=]*)=(?P<path>.*)$")


Nit: I believe ?P<name> is just a longer form of ?<name>, and in that case we might as well use the shorter syntax without P.

(I notice that compiletest currently uses an inconsistent mixture of both styles.)

Yeah I wondered if I should have P or not and noticed it was used in other places, so I kept it. I don't mind removing it though. Done.

Zalathar · 2026-01-24T03:03:59Z

src/tools/compiletest/src/directives/auxiliary.rs

+    //   modifiers:name=path
+    let caps = static_regex!(r"^(?:(?P<modifiers>[^=]*?):)?(?P<name>[^=]*)=(?P<path>.*)$")
+        .captures(r.trim())
+        .unwrap_or_else(|| panic!("missing aux-crate value (e.g. log=log.rs)"));


If I understand correctly, this error is shown if the value couldn't be parsed, so it should probably say “couldn't parse aux-crate value” and maybe include the value string, too.

I intentionally didn't want to make this PR change behavior or error message, but I agree it is nicer to print what value that couldn't be parse, so I added that.

Zalathar · 2026-01-24T03:05:35Z

src/tools/compiletest/src/directives/auxiliary.rs

+    let name = caps.name("name").map(|m| m.as_str().to_string()).unwrap_or_default();
+    let path = caps.name("path").map(|m| m.as_str().to_string()).unwrap_or_default();


If the regex match succeeded, then name and path should always be present, so these can probably just be caps["name"].to_owned() or similar.

Hmm I don't think there is something like to_owned()? .name("name") returns an Option<Match>. If there is a simpler way to write this I wasn't able to figure it out.

regex::Captures implements Index<&str>, so instead of writing caps.get("name") it should be possible to write caps["name"] to get a &str (panicking if that named group didn't match), and then convert that to String.

Oh... Thanks. Done.

Zalathar · 2026-01-24T03:13:47Z

Could you please also add at least one unit test for parse_aux_crate with extern modifiers, just to double-check that the modifiers are being parsed as we expect.

(Doesn't need to be super thorough; I just want some explicit assurance that the modifiers don't accidentally end up in the name after all.)

Zalathar · 2026-01-24T03:39:14Z

Should be good to go after this last round of nitpicks.

@rustbot author

Enselic · 2026-01-24T11:26:57Z

Could you please also add at least one unit test for parse_aux_crate with extern modifiers, just to double-check that the modifiers are being parsed as we expect.

Sure, no problem. Done.

Note however that you can be confident that parsing works even without the new tests, because if e.g. modifiers failed to parse properly, a lot of tests that depend on them would fail (like tests/ui/privacy/pub-priv-dep/pub-priv1.rs just to give one example).

@rustbot ready

Zalathar · 2026-01-24T12:46:20Z

Thanks.

@bors r+

@Zalathar

compiletest: Make `aux-crate` directive explicitly handle `--extern` modifiers With `-Zunstable-options` it is possible to pass options to `--extern`. See here for an exhaustive list of possible options: https://github.com/rust-lang/rust/blob/b5dd72d2921500c9d9e15f074e1d831adcaa3dee/compiler/rustc_session/src/config.rs#L2356-L2367 Using these options works with the `aux-crate` directive, but only because the options pretend to be part of the name. Make it clearer what `aux-crate` supports by explicitly handling `--extern` options. This PR is step one of splitting up rust-lang#151258 into smaller pieces. r? @Zalathar

@ghost

…uwer Rollup of 3 pull requests Successful merges: - #151346 (add `simd_splat` intrinsic) - #151353 (compiletest: Make `aux-crate` directive explicitly handle `--extern` modifiers) - #151571 (Fix cstring-merging test for Hexagon target) r? @ghost

JonathanBrouwer · 2026-01-24T15:04:34Z

@bors r-
#151586 (comment)

rust-bors · 2026-01-24T15:04:37Z

📋 Only unclosed PRs can be unapproved.

JonathanBrouwer · 2026-01-24T15:05:03Z

(Whoops did not mean to close this)
@rustbot author

@Zalathar

compiletest: Make `aux-crate` directive explicitly handle `--extern` modifiers With `-Zunstable-options` it is possible to pass options to `--extern`. See here for an exhaustive list of possible options: https://github.com/rust-lang/rust/blob/b5dd72d2921500c9d9e15f074e1d831adcaa3dee/compiler/rustc_session/src/config.rs#L2356-L2367 Using these options works with the `aux-crate` directive, but only because the options pretend to be part of the name. Make it clearer what `aux-crate` supports by explicitly handling `--extern` options. This PR is step one of splitting up rust-lang#151258 into smaller pieces. r? @Zalathar

…modifiers To make it clearer what happens. In other words, do not silently keep modifiers as part of `AuxCrate::name`.

rust-bors · 2026-01-24T15:08:12Z

⚠️ A new commit 6f767b686044e59e37c31b17a8f00cac7092fa7c was pushed to the branch, the PR will need to be re-approved.

Enselic · 2026-01-24T15:08:52Z

Trivial fix.

@bors r=Zalathar

rust-bors · 2026-01-24T15:08:55Z

📌 Commit 6f767b6 has been approved by Zalathar

It is now in the queue for this repository.

@Zalathar

compiletest: Make `aux-crate` directive explicitly handle `--extern` modifiers With `-Zunstable-options` it is possible to pass options to `--extern`. See here for an exhaustive list of possible options: https://github.com/rust-lang/rust/blob/b5dd72d2921500c9d9e15f074e1d831adcaa3dee/compiler/rustc_session/src/config.rs#L2356-L2367 Using these options works with the `aux-crate` directive, but only because the options pretend to be part of the name. Make it clearer what `aux-crate` supports by explicitly handling `--extern` options. This PR is step one of splitting up rust-lang#151258 into smaller pieces. r? @Zalathar

@ghost

…uwer Rollup of 3 pull requests Successful merges: - #151346 (add `simd_splat` intrinsic) - #151353 (compiletest: Make `aux-crate` directive explicitly handle `--extern` modifiers) - #151571 (Fix cstring-merging test for Hexagon target) r? @ghost

Rollup of 11 pull requests Successful merges: - #149962 (Promote powerpc64-unknown-linux-musl to tier 2 with host tools) - #150138 (Add new Tier 3 targets for ARMv6) - #150905 (Fix(lib/win/net): Remove hostname support under Win7) - #151094 (remote-test-server: Fix compilation on UEFI targets) - #151346 (add `simd_splat` intrinsic) - #151353 (compiletest: Make `aux-crate` directive explicitly handle `--extern` modifiers) - #151538 (std: `sleep_until` on Motor and VEX) - #151098 (Add Korean translation to Rust By Example) - #151157 (Extend build-manifest local test guide) - #151403 (std: use 64-bit `clock_nanosleep` on GNU/Linux if available) - #151571 (Fix cstring-merging test for Hexagon target)

@Zalathar

Rollup merge of #151353 - Enselic:aux-crate-opts, r=Zalathar compiletest: Make `aux-crate` directive explicitly handle `--extern` modifiers With `-Zunstable-options` it is possible to pass options to `--extern`. See here for an exhaustive list of possible options: https://github.com/rust-lang/rust/blob/b5dd72d2921500c9d9e15f074e1d831adcaa3dee/compiler/rustc_session/src/config.rs#L2356-L2367 Using these options works with the `aux-crate` directive, but only because the options pretend to be part of the name. Make it clearer what `aux-crate` supports by explicitly handling `--extern` options. This PR is step one of splitting up #151258 into smaller pieces. r? @Zalathar

Rollup of 11 pull requests Successful merges: - rust-lang/rust#149962 (Promote powerpc64-unknown-linux-musl to tier 2 with host tools) - rust-lang/rust#150138 (Add new Tier 3 targets for ARMv6) - rust-lang/rust#150905 (Fix(lib/win/net): Remove hostname support under Win7) - rust-lang/rust#151094 (remote-test-server: Fix compilation on UEFI targets) - rust-lang/rust#151346 (add `simd_splat` intrinsic) - rust-lang/rust#151353 (compiletest: Make `aux-crate` directive explicitly handle `--extern` modifiers) - rust-lang/rust#151538 (std: `sleep_until` on Motor and VEX) - rust-lang/rust#151098 (Add Korean translation to Rust By Example) - rust-lang/rust#151157 (Extend build-manifest local test guide) - rust-lang/rust#151403 (std: use 64-bit `clock_nanosleep` on GNU/Linux if available) - rust-lang/rust#151571 (Fix cstring-merging test for Hexagon target)

rustbot assigned Zalathar Jan 19, 2026

Enselic mentioned this pull request Jan 19, 2026

compiletest: Support --extern options with proc-macro directive #151258

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rustc-dev-guide: Mention --extern modifiers for aux-crate directive

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Enselic force-pushed the aux-crate-opts branch from 5028acf to 41c6301 Compare January 19, 2026 19:48

Enselic changed the title ~~compiletest: Make aux-crate directive explicitly handle --extern options~~ compiletest: Make aux-crate directive explicitly handle --extern modifiers Jan 19, 2026

Enselic force-pushed the aux-crate-opts branch from 41c6301 to 8d3e25a Compare January 22, 2026 05:16

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Enselic force-pushed the aux-crate-opts branch from be2b322 to fde37c3 Compare January 24, 2026 12:24

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Rollup of 3 pull requests #151586

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Rollup of 3 pull requests #151597

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compiletest: Make aux-crate directive explicitly handle --extern …

6f767b6

…modifiers To make it clearer what happens. In other words, do not silently keep modifiers as part of `AuxCrate::name`.

Enselic force-pushed the aux-crate-opts branch from fde37c3 to 6f767b6 Compare January 24, 2026 15:08

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Rollup of 3 pull requests #151598

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Rollup of 11 pull requests #151615

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rust-bors bot merged commit 0a1b437 into rust-lang:main Jan 25, 2026
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rustbot added this to the 1.95.0 milestone Jan 25, 2026

	"priv" => is_private_dep = true,
	"noprelude" => {
	if let ExternLocation::ExactPaths(_) = &entry.location {
	add_prelude = false;
	} else {
	early_dcx.early_fatal(
	"the `noprelude` --extern option requires a file path",
	);
	}
	}
	"nounused" => nounused_dep = true,
	"force" => force = true,

		/// With `aux-crate: noprelude:foo=bar.rs` this will be `noprelude`.
		pub extern_opts: Option<String>,

		let name = caps.name("name").map(\|m\| m.as_str().to_string()).unwrap_or_default();
		let path = caps.name("path").map(\|m\| m.as_str().to_string()).unwrap_or_default();

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compiletest: Make aux-crate directive explicitly handle --extern modifiers #151353

compiletest: Make aux-crate directive explicitly handle --extern modifiers #151353

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compiletest: Make `aux-crate` directive explicitly handle `--extern` modifiers #151353

compiletest: Make `aux-crate` directive explicitly handle `--extern` modifiers #151353

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