Support multiple artifact dependency aliases to the same package by npmccallum · Pull Request #17067 · rust-lang/cargo

npmccallum · 2026-06-03T14:55:35Z

This fills in a behavior described by RFC 3176 that was not implemented when artifact dependencies were initially added.

The RFC allows a package to be declared multiple times under different dependency names, with each declaration selecting a different artifact target. Cargo rejected several of those same-package artifact dependency forms as duplicate renamed dependencies. This PR allows the all-artifact cases while keeping the existing duplicate-name checks for mixed artifact/non-artifact dependency cases.

The series is split into reviewable commits:

Add tests for the current duplicate-name behavior.
Extract shared dependency-name helpers in the resolver.
Allow artifact aliases when lowering build and unit graph edges.
Report artifact alias names consistently in cargo metadata.
Document the supported alias form and the lib = true restriction.

The lib = true case still requires Cargo to refer to the package library with one Rust extern crate name. Multiple artifact aliases that would give the library different extern names continue to be rejected.

Closes #12374

FYI @joshtriplett @Byron

rustbot · 2026-06-03T14:55:41Z

r? @weihanglo

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Owners of files modified in this PR: @ehuss, @epage, @weihanglo
@ehuss, @epage, @weihanglo expanded to ehuss, epage, weihanglo
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npmccallum · 2026-06-24T17:23:00Z

@weihanglo are you able to review this? If not, maybe @ehuss could?

weihanglo

Thanks for the contribution. Unfortunately, I may not have sufficient bandwidth to do meaningful reviews within this week or next week. Feel free to reassign.

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npmccallum · 2026-06-24T20:06:26Z

@rustbot reroll

epage · 2026-06-24T20:14:13Z

Note that in general, there is a lot less review bandwidth at this time. Weihang has the most bandwidth and he said he wouldn't be available. We'll see when/if I have time.

epage

Only had a quick glance at the tests.

The fixes seem to be independent. Can you split them up into smaller commits / reviewable unit?

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epage · 2026-06-24T20:17:49Z

+                authors = []
+                resolver = "2"
+
+                [dependencies.bar]


Is this mimicking existing tests? I at least would prefer we only use inline tables for deps, not standard tables.

epage · 2026-06-24T20:20:54Z

+
+    p.cargo("build --unit-graph -Zunstable-options -Z bindeps")
+        .masquerade_as_nightly_cargo(&["unit-graph", "bindeps"])
+        .with_stdout_contains(r#"[..]"index":0,"extern_crate_name":"bar"[..]"#)


Is this mimicking an existing pattern? We try to avoid the _contains functions

npmccallum · 2026-06-26T16:58:20Z

I split this into smaller commits:

current-behavior tests
resolver naming helper
build/unit-graph behavior
metadata behavior
docs

I also adjusted the tests from the inline comments to use inline dependency tables and a structured unit-graph stdout assertion.

weihanglo · 2026-06-26T20:02:44Z

May have time for this, though let me pick up the RFC first.

rustbot · 2026-07-03T14:16:49Z

This PR was rebased onto a different master commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

npmccallum · 2026-07-04T13:12:14Z

@joshtriplett This is my next highest priority if you have cycles. With this feature, arma can generate PMIs cross-architecture.

Add regression coverage for the current invariant that multiple dependency declarations to the same package are rejected when they would require distinct dependency names. This makes the existing behavior explicit before relaxing the artifact-dependency cases tracked in rust-lang#12374.

Extract dependency-name calculation so artifact alias handling can use the same extern crate naming rules in build graph lowering and metadata output.

Permit all-artifact aliases to the same package to keep their dependency-specific names when lowering build and unit graph edges. Mixed artifact and non-artifact dependencies still use the existing duplicate-name check so library dependencies have one extern crate name.

Use the shared dependency-name rules when emitting cargo metadata for artifact aliases to the same package. Bin-only artifact aliases emit dependency-specific extern names, while lib aliases continue to require a single library dependency name.

Document declaring separate aliases when building artifacts from the same package for multiple target platforms. Also call out that multiple lib=true aliases must agree on one library extern crate name.

epage · 2026-07-22T18:09:28Z

+            .unwrap_or_else(|| (to_target.crate_name().into(), None))
+    }
+
+    pub fn lib_dependency_name<'a>(


This appears to be dead code within this commit

View changes since the review

epage · 2026-07-22T18:09:40Z

+        Ok((extern_crate_name, dep_name))
+    }
+
+    pub fn dep_extern_crate_name_and_dep_name(


Doesn't look like this needs to be pub within this commit

View changes since the review

epage · 2026-07-22T18:12:31Z

-                [build-dependencies.bar]
-                path = "bar/"
-                artifact = "bin"
-                target = "{}"
-
-                [build-dependencies.bar-native]
-                package = "bar"
-                path = "bar/"
-                artifact = "bin"
-                target = "{}"
+                [build-dependencies]
+                bar = {{ path = "bar/", artifact = "bin", target = "{}" }}
+                bar-native = {{ package = "bar", path = "bar/", artifact = "bin", target = "{}" }}


Was this style change made in the wrong commit? It makes it harder to see what may be intentional changes fthat go with this fix

View changes since the review

epage · 2026-07-22T18:13:32Z

-        .with_status(101)
-        .with_stderr_data(str![[r#"
-[LOCKING] 1 package to latest compatible version
-[ERROR] the crate `foo v0.0.0 ([ROOT]/foo)` depends on crate `bar v0.5.0 ([ROOT]/foo/bar)` multiple times with different names
-
-"#]])
+        .with_stderr_contains(
+            "[RUNNING] `rustc --crate-name bar --edition=2015 bar/src/main.rs [..]--target [ALT_TARGET] [..]",
+        )


What is the goal with using with_stderr_contains with this line of verbose output?

For context, we try to minimize the use of _contains assertions because we can't do snapshotting with them

View changes since the review

epage · 2026-07-22T18:13:56Z

+#[cargo_test]
+fn multiple_artifact_aliases_no_op_rebuild() {


Why is a new test being added in a non-test commit?

View changes since the review

epage · 2026-07-22T18:15:17Z

+        .with_stdout_contains(r#"[..]"rename":"bar-lib"[..]"#)
+        .with_stdout_contains(r#"[..]"rename":"bar-bin"[..]"#)
+        .with_stdout_contains(r#"[..]"extern_name":"bar_lib"[..]"#)
+        .with_stdout_contains(r#"[..]"extern_name":"bar_bin"[..]"#)


The lack of context is another problem with _contains assertions: I was looking to the test to better understand a part of your change and I can't tell what is happening from this

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rustbot assigned weihanglo Jun 3, 2026

rustbot added A-dependency-resolution Area: dependency resolution and the resolver A-documenting-cargo-itself Area: Cargo's documentation Command-metadata S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jun 3, 2026

npmccallum mentioned this pull request Jun 4, 2026

feat(tree): show artifact dependency details #17075

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weihanglo reviewed Jun 24, 2026

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rustbot assigned epage and unassigned weihanglo Jun 24, 2026

epage reviewed Jun 24, 2026

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npmccallum force-pushed the master branch from 0294a83 to df3e262 Compare June 26, 2026 16:58

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npmccallum force-pushed the master branch 2 times, most recently from 4546761 to 55cb078 Compare July 3, 2026 14:16

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npmccallum added 5 commits July 19, 2026 20:05

refactor(resolve): share dependency name helpers

81bc025

Extract dependency-name calculation so artifact alias handling can use the same extern crate naming rules in build graph lowering and metadata output.

docs(bindeps): show artifact aliases per target

a67fa8b

Document declaring separate aliases when building artifacts from the same package for multiple target platforms. Also call out that multiple lib=true aliases must agree on one library extern crate name.

npmccallum force-pushed the master branch from 55cb078 to a67fa8b Compare July 20, 2026 00:09

epage reviewed Jul 22, 2026

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		#[cargo_test]
		fn multiple_artifact_aliases_no_op_rebuild() {

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