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cargo-bazel: fix binary targets of proc-macro crates using wrong dep attribute#3975

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lamcw wants to merge 2 commits intobazelbuild:mainfrom
lamcw:fix-proc-macro-crates-use-deps
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cargo-bazel: fix binary targets of proc-macro crates using wrong dep attribute#3975
lamcw wants to merge 2 commits intobazelbuild:mainfrom
lamcw:fix-proc-macro-crates-use-deps

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@lamcw lamcw commented Apr 17, 2026

Problem

When a crate has both a rust_proc_macro library target and rust_binary targets (e.g. development utilities shipped alongside the proc-macro), make_rust_binary unconditionally places the library in deps. However, rules_rust validates that proc-macro libraries must appear in proc_macro_deps, not deps. This causes analysis failures for any such crate.

Solution

In make_rust_binary, detect whether the crate's library target is a proc-macro by checking if Rule::ProcMacro(_) is present in krate.targets. If it is, insert the library label into proc_macro_deps instead of deps.

Testing

  • binary_of_proc_macro_crate_uses_proc_macro_deps: verifies that the generated rust_binary has the proc-macro lib in proc_macro_deps and not in deps.

lamcw added 2 commits April 17, 2026 10:26
…attribute

Problem:
When a crate has both a rust_proc_macro library target and rust_binary
targets (e.g. development utilities shipped alongside the proc-macro),
make_rust_binary unconditionally places the library in `deps`. However,
rules_rust validates that proc-macro libraries must appear in
`proc_macro_deps`, not `deps`. This causes analysis failures for any
such crate.

Solution:
In make_rust_binary, detect whether the crate's library target is a
proc-macro by checking if Rule::ProcMacro(_) is present in krate.targets.
If it is, insert the library label into proc_macro_deps instead of deps.

Testing:
- binary_of_proc_macro_crate_uses_proc_macro_deps: verifies that the
  generated rust_binary has the proc-macro lib in proc_macro_deps and
  not in deps.
Signed-off-by: Thomas Lam <[email protected]>
@lamcw lamcw marked this pull request as ready for review April 17, 2026 02:49
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