refactor(uv): expand templates instead of .format() strings in uv_hub by xangcastle · Pull Request #1496 · aspect-build/rules_py

xangcastle · 2026-08-28T02:43:12Z

The hub repository rule was assembling its BUILD and .bzl files out of .format() strings, which meant doubling every brace in the generated Starlark and burying the skeletons inside the implementation.

This moves the static parts into five .tmpl files under uv/private/uv_hub/templates and expands them with repository_ctx.template, so the rule now only computes the dynamic bits: select arms, the group inversion, label lists.

Net effect is about ninety fewer lines, and the templates read as plain Starlark. Output is byte-for-byte identical, regenerating the snapshots produced an empty diff. Docstrings got a pass while I was in there: _hub_impl now documents the five artifacts and their invariants.

Changes are visible to end-users: no

Test plan

Covered by existing test cases

coderabbitai · 2026-08-28T02:43:20Z

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aspect-workflows · 2026-08-28T02:43:41Z

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github-actions · 2026-08-28T02:50:28Z

py_binary startup benchmark

Version	Mean (ms)	Median (ms)	± stddev	vs BCR	vs main	Build (s)
BCR 1.11.7 (baseline)	160.649	160.735	±1.635	—	—	1.61
HEAD main	56.854	56.622	±1.585	-64.8%	—	1.76
This PR	56.325	56.232	±0.773	-65.0%	-0.7%	1.53

Measured with hyperfine --warmup 5 --runs 50 --shell=none on Linux
Gate: PR vs HEAD main median (threshold: 10%, and must exceed the 2×SE noise floor, here 0.9%). BCR is shown only as a historical baseline.
Build time: cold bazel build //:bench with isolated output base, no disk cache; external repos prefetched so network is excluded.

sys.path quality

Version	sys.path entries	distinct site-packages roots
BCR 1.11.7 (baseline)	6	1
HEAD main	7	2
This PR	7	2

sys.path quality measured by bench_syspath inside the assembled venv. Duplicate realpaths indicate symlink redundancy; many distinct site-packages roots suggest an inefficient venv layout.

Bazel analysis benchmark

Version	Mean (ms)	Median (ms)	± stddev	vs BCR	vs main	Targets	Actions
BCR 2.0.0-alpha.6 (baseline)	1156.913	1123.924	±165.282	—	—	304	13746
HEAD main	1162.719	1073.843	±199.579	-4.5%	—	304	13546
This PR	1167.795	1134.669	±189.931	+1.0%	+5.7%	304	13546

Measured with hyperfine --warmup 1 --runs 10 on Linux
Gate: PR vs HEAD main median (threshold: 10%, and must exceed the 2×SE noise floor, here 16.2%). BCR is shown only as a historical baseline.
Command: warm-server bazel build --nobuild //workspace/..., analysis cache discarded each run via a fresh --action_env value; no disk cache.

py_image_layer benchmark

Scenario	Version	Mean (s)	Median (s)	± stddev	Actions	vs BCR	vs main
Analysis	BCR 2.0.0-alpha.6 (baseline)	0.71	0.64	±0.14	747	—	—
Analysis	HEAD main	0.69	0.65	±0.14	726	+1.8%	—
Analysis	This PR	0.67	0.61	±0.14	726	-4.6%	-6.4%
1p Source Change	BCR 2.0.0-alpha.6 (baseline)	0.71	0.71	±0.05	4	—	—
1p Source Change	HEAD main	0.75	0.72	±0.08	5	+1.9%	—
1p Source Change	This PR	0.71	0.70	±0.04	5	-1.9%	-3.7%
3p Source Change	BCR 2.0.0-alpha.6 (baseline)	0.86	0.85	±0.04	5	—	—
3p Source Change	HEAD main	0.90	0.89	±0.02	6	+4.8%	—
3p Source Change	This PR	0.90	0.90	±0.03	6	+5.4%	+0.6%

Measured with hyperfine on Linux, building //workspace:image_layers (10 binaries, ~30-wheel dep pool, grouped first-party/pip/interpreter tier) with isolated output base, no disk cache.
Scenarios: analysis = warm-server bazel build --nobuild, re-analyzed each run via a fresh --action_env value; incrementals run against a built state with warm analysis: source = append to the last package's lib.py, wheel = rewrite click post_install_patches content.
Actions: for Analysis, the total action count behind the image target from aquery deps(...); for incrementals, actions re-executed for the mutation, from a single instrumented run's BEP build metrics (deterministic; per-mnemonic breakdown in the *-actions.json artifacts). Informational only, not gated.
Gate: PR vs HEAD main median per scenario (threshold: 10%, and must exceed the 2×SE noise floor). BCR is shown only as a historical baseline.

xangcastle · 2026-08-28T02:51:33Z

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chatgpt-codex-connector · 2026-08-28T02:54:35Z

Codex Review: Didn't find any major issues. 🚀

Reviewed commit: 301cd977b3

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jbedard · 2026-08-28T05:39:38Z

+package(default_visibility = ["//uv/private:__subpackages__"])
+
+exports_files([
+    "defs.tmpl",


I think these should be named *.tmpl.{bazel,bzl} so we actually know what type of file they are, and an IDE will render them correctly etc

if I add .bzl at the end, gazelle will try to generate bzl_libraries

We could tell gazelle to ignore *.tmpl.* maybe?

ok, let me try

refactor(uv): expand templates instead of .format() strings in uv_hub

301cd97

xangcastle marked this pull request as ready for review August 28, 2026 02:54

xangcastle requested a review from jbedard August 28, 2026 02:55

xangcastle enabled auto-merge (squash) August 28, 2026 02:57

jbedard reviewed Aug 28, 2026

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xangcastle requested a review from jbedard August 28, 2026 12:36

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refactor(uv): expand templates instead of .format() strings in uv_hub - #1496

refactor(uv): expand templates instead of .format() strings in uv_hub#1496
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py_binary startup benchmark

sys.path quality

Bazel analysis benchmark

py_image_layer benchmark

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