toolchain: defer driver materialization for runtime-only builds#57
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Problem Solved ChiliRT wheel builds need the XLS runtime files from a registered workspace toolchain without paying the cost of materializing `xlsynth-driver`. Before this change, loading a registered toolchain could still require driver configuration or stage placeholder driver artifacts, which made runtime-only consumers depend on a tool they do not use. Implementation Split the module-extension surface into runtime and toolchain repositories. The runtime repository materializes tools, DSLX stdlib, `libxls`, and runtime metadata without resolving any driver input. The toolchain repository remains loadable metadata until a driver-backed action is built. Real driver actions now materialize `xlsynth-driver` lazily from a declared Bazel action input when the consumer supplied a local or installed driver path. `auto` driver inputs are validated before use and fall back to download-backed materialization when the declared installed driver is not usable. `local_paths` driver materialization requires the configured `local_driver_path` and rejects declared inputs that do not resolve to that file, so placeholder driver files cannot masquerade as real drivers. The registered runtime-only smoke coverage now runs directly from presubmit and checks both halves of the contract: runtime-only builds do not materialize the driver, while explicit missing-driver builds fail with an actionable configuration error. Validation - python3 artifact_resolution_test.py - env BAZELISK_HOME=/tmp/rue-bazelisk-cache python3 run_presubmit.py -k registered - env BAZELISK_HOME=/tmp/rue-bazelisk-cache bazel test //:artifact_resolution_test //:external_bundle_exports_test --test_output=errors - python3 -m py_compile materialize_xls_bundle.py artifact_resolution_test.py registered_toolchain_smoke.py run_presubmit.py pr:runtime-only-xls-toolchain
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meheff
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Apr 15, 2026
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Problem Solved
Some builds need the XLS runtime files from a registered workspace
toolchain without paying the cost of materializing
xlsynth-driver. Beforethis change, loading a registered toolchain could still require driver
configuration or stage placeholder driver artifacts, which made runtime-only
consumers depend on a tool they do not use.
Implementation
Split the module-extension surface into runtime and toolchain repositories.
The runtime repository materializes tools, DSLX stdlib,
libxls, and runtimemetadata without resolving any driver input. The toolchain repository remains
loadable metadata until a driver-backed action is built.
Real driver actions now materialize
xlsynth-driverlazily from a declaredBazel action input when the consumer supplied a local or installed driver path.
autodriver inputs are validated before use and fall back to download-backedmaterialization when the declared installed driver is not usable.
local_pathsdriver materialization requires the configured
local_driver_pathand rejectsdeclared inputs that do not resolve to that file, so placeholder driver files
cannot masquerade as real drivers.
The registered runtime-only smoke coverage now runs directly from presubmit and
checks both halves of the contract: runtime-only builds do not materialize the
driver, while explicit missing-driver builds fail with an actionable
configuration error.
Stack: