feat(covgate): report build-cache pre-warm duration#35
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The pre-warm pass before the parallel coverage runs was invisible: it is
excluded from "Total time" (which times only the parallel phase) and emitted
no output, so its cost could not be observed or compared run-to-run.
Announce the pass ("Pre-warming build cache (N packages)...") and report its
wall time on completion ("Pre-warm complete in X"). Extract the warm logic
into prewarmCache so run() stays within the function-length limit.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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## What Reverts the covgate **build-cache pre-warm** feature in its entirety. covgate no longer pre-warms the Go build cache before its parallel coverage runs. Reverts, in order (newest first): - #36 `perf(covgate): instrument the build-cache pre-warm` (`794e725`) - #35 `feat(covgate): report build-cache pre-warm duration` (`6a0cc47`) - #34 `perf(covgate): pre-warm build cache before parallel coverage runs` (`0c3c0af`) ## Why We no longer want covgate to pre-warm the build cache. The pre-warm compiled an extra artifact set that inflated the CI `gobuild-test` cache and pushed the backend repo back over the 10 GB Actions cache quota (the very regression #36 tried to walk back). Rather than keep iterating on the pre-warm, we're removing it. ## How Three `git revert` commits, preserving history/attribution. The reverted `internal/services/covgate/` and `internal/services/gocover/` files are **byte-identical** to their pre-feature state, and the feature's design doc (`plans/completed/20260624-covgate-prewarm-build-cache.md`) is removed. ## Validation - No lingering `prewarm` / `PrewarmBuild` references anywhere in `internal/`, `cmd/`, or `scripts/`. - Full `scripts/preflight.sh` passes clean: covgate coverage 94.3% across all 30 packages, gocover 92.6% (≥ 92.1% required), custom lint + gofumpt + golangci-lint + deadcode + surface-lint all green. - Clean revert with no conflicts against current `main`; unrelated later commits (#37 CI, #38 dep bumps, #39 max-param-count) required no adjustment. 🤖 Generated with [Claude Code](https://claude.com/claude-code) <!-- codesmith:footer --> --- <a href="https://app.blacksmith.sh/mirurobotics/codesmith/gotools/pr/40"><picture><source media="(prefers-color-scheme: dark)" srcset="https://pr-comments-assets.blacksmith.sh/codesmith/view-with-codesmith-dark-v2.svg"><source media="(prefers-color-scheme: light)" srcset="https://pr-comments-assets.blacksmith.sh/codesmith/view-with-codesmith-light-v2.svg"><img alt="View with Codesmith" src="https://pr-comments-assets.blacksmith.sh/codesmith/view-with-codesmith-dark-v2.svg"></picture></a> <a href="https://backend.blacksmith.sh/track/enable-autofix?expires=1785713638&installation_id=142588636&pr_number=40&repository=mirurobotics%2Fgotools&return_to=https%3A%2F%2Fgithub.com%2Fmirurobotics%2Fgotools%2Fpull%2F40&signature=00cc206a36c548207ac3606f293163ba579f08070387cbe5cc6ca77ed2f8cb48"><picture><source media="(prefers-color-scheme: dark)" srcset="https://pr-comments-assets.blacksmith.sh/codesmith/autofix-with-codesmith-dark.svg"><source media="(prefers-color-scheme: light)" srcset="https://pr-comments-assets.blacksmith.sh/codesmith/autofix-with-codesmith-light.svg"><img alt="Autofix with Codesmith" src="https://pr-comments-assets.blacksmith.sh/codesmith/autofix-with-codesmith-dark.svg"></picture></a> <sup>Need help on this PR? Tag <code>/codesmith</code> with what you need. Autofix is disabled.</sup> <!-- codesmith:autofix:disabled --> <!-- /codesmith:footer -->
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What
Make the covgate build-cache pre-warm pass observable: announce it and report its wall time.
Why
The pre-warm pass (added in #34) is a large slice of a covgate run but was invisible: it's deliberately excluded from "Total time" (which times only the parallel coverage phase) and emitted no output. So you couldn't see how long it took, or tell whether it was helping — which is exactly the situation that prompted this: a downstream run where the pre-warm appeared to underperform, with no way to confirm from the logs.
Change
Pre-warming build cache (N packages)...before it andPre-warm complete in Xafter, to the same writer as the rest of the output.prewarmCache(...)sorun()stays within the repo's function-length limit.No behavior change to coverage measurement, thresholds, exclude handling, gating (
parallelism > 1 && len(pkgs) > 1), or "Total time" — purely additive observability.Tests
TestRun_Prewarm_InvokedOnce_WhenParallelAndMultiPkgto assert both new lines appear.TestRun_Prewarm_Skipped_WhenSinglePackageOrSerialto assert they do not appear when the pass is gated off.Context
This is the diagnostic prerequisite for an observed regression: when a downstream repo (backend) switched from a CI-side pre-warm step to covgate's internal self-warm, the combined warm + coverage time looked worse than the external step. With this output we can measure the pre-warm and coverage phases separately on a clean run and confirm the cause before changing the warm logic.
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