Add setting always_enable_metadata_output_groups#3524
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illicitonion merged 1 commit intobazelbuild:mainfrom Aug 25, 2025
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Add setting always_enable_metadata_output_groups#3524illicitonion merged 1 commit intobazelbuild:mainfrom
always_enable_metadata_output_groups#3524illicitonion merged 1 commit intobazelbuild:mainfrom
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Right now, only library targets provide metadata-related output groups. This makes sense for compilation purposes, but building the metadata is also useful for other things; namely, building *only* the metadata is the fastest way to get diagnostic information for your workspace like `cargo check` does. This PR adds a new setting, `always_enable_metadata_output_groups`, that enables both the `build_metadata` and `rustc_rmeta_output` output groups for non-library targets (such as binaries and tests). That means that the presence of metadata in `CrateInfo` can no longer be used to determine pipelind compilation support, so a new attribute, `metadata_supports_pipelining`, is added for that purpose. As an example of the performance increase, compare a `bazel build` on a binary w/o `--output_groups=rustc_rmeta_output`: ``` INFO: Elapsed time: 2.247s, Critical Path: 2.11s ``` to with it: ``` INFO: Elapsed time: 1.034s, Critical Path: 0.90s ```
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[#3524](bazelbuild/rules_rust#3524) in rules_rust adds a `metadata_supports_pipelining` parameter to `rustc_compile_action()` that must be passed explicitly for pipelining to work. We do this similarly to the change to prost.bzl in #3524. Without this, the `pipelined_compilation_of_bindings_test` fails. PiperOrigin-RevId: 803363443 Change-Id: I017f5d869eec612a9114be6b3767316241e669d1
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Right now, only library targets provide metadata-related output groups. This makes sense for compilation purposes, but building the metadata is also useful for other things; namely, building only the metadata is the fastest way to get diagnostic information for your workspace like
cargo checkdoes.This PR adds a new setting,
always_enable_metadata_output_groups, that enables both thebuild_metadataandrustc_rmeta_outputoutput groups for non-library targets (such as binaries and tests). That means that the presence of metadata inCrateInfocan no longer be used to determine pipelind compilation support, so a new attribute,metadata_supports_pipelining, is added for that purpose.As an example of the performance increase, compare a
bazel buildon a binary w/o--output_groups=rustc_rmeta_output:to with it: