Output mypy cache as a zip file instead of a tree artifact#138
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Previously, the output of `mypy_runner.py` was declared as a tree artifact (`declare_directory`). This PR changes it to a single zip file (`declare_file`) instead, which works better with bazel remote cache. Zip was chosen over other archive formats (for example, `tar.gz`) because it supports random access, allowing individual entries to be skipped or extracted without reading the entire archive. File compression is explicitly disabled (`ZIP_STORED`) because each target produces a full accumulated cache containing mypy results for all transitive dependencies. Enabling compression would force every target to recompress the outputs of its entire transitive closure on each build, wasting CPU time. A follow-up PR will address the cache accumulation issue by outputting only the cache entries produced by an individual rule. This implementation showed a ~10% speedup in local runs, likely due to reducing the number of files bazel needs to copy between sandboxes.
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Previously, the output of
mypy_runner.pywas declared as a tree artifact (declare_directory). This PR changes it to a single zip file (declare_file) instead, which works better with bazel remote cache.Zip was chosen over other archive formats (for example,
tar.gz) because it supports random access, allowing individual entries to be skipped or extracted without reading the entire archive. File compression is explicitly disabled (ZIP_STORED) because each target produces a full accumulated cache containing mypy results for all transitive dependencies. Enabling compression would force every target to recompress the outputs of its entire transitive closure on each build, wasting CPU time.A follow-up PR will address the cache accumulation issue by outputting only the cache entries produced by an individual rule.
This implementation showed a ~10% speedup in local runs, likely due to reducing the number of files bazel needs to copy between sandboxes.