internal/ci: skip the test cache via GOFLAGS=-count=1

I verified that GOFLAGS=-count=1 does not break cmd/go subcommands
which don't take this flag, such as vet. It seems like GOFLAGS
is implemented such that it knows chich commands support which flags.

The previous comments were also somewhat confused; the use of -count=1
does not break the test caches on the trybot repo, because this step
does not run on the trybot repo at all.

It seems to me like the only reason we used `go clean -testcache`
over `GOFLAGS=-count=1` was to keep the cache sizes lean.
This is no longer a factor with Namespace runners.

Signed-off-by: Daniel Martí <[email protected]>
Change-Id: I2c45e1384fb6f1c547e5c5dc60388d89c154a59f
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1217815
TryBot-Result: CUEcueckoo <[email protected]>
Reviewed-by: Paul Jolly <[email protected]>
Unity-Result: CUE porcuepine <[email protected]>

Author: mvdan

.github/workflows/trybot.yaml

@@ -84,7 +84,7 @@ jobs:
       - if: |-
           github.repository == 'cue-lang/cue' && (((github.ref == 'refs/heads/master' || startsWith(github.ref, 'refs/heads/release-branch.')) && (! (contains(github.event.head_commit.message, '
           Dispatch-Trailer: {"type":"')))) || (github.ref == 'refs/heads/ci/test'))
-        run: go clean -testcache
+        run: go env -w GOFLAGS=-count=1
       - run: go run cuelang.org/go/cmd/cue login --token=${{ secrets.NOTCUECKOO_CUE_TOKEN }}
       - if: (matrix.go-version == '1.24.x' && matrix.runner == 'namespace-profile-ubuntu-24-04-amd64-8x16')
         name: Early git and code sanity checks

internal/ci/base/github.cue

@@ -159,22 +159,14 @@ setupGoActionsCaches: [
 		with: cache: "go"
 	},
 
-	// All tests on protected branches should skip the test cache.  The
-	// canonical way to do this is with -count=1. However, we want the
-	// resulting test cache to be valid and current so that subsequent CLs
-	// in the trybot repo can leverage the updated cache. Therefore, we
-	// instead perform a clean of the testcache.
+	// All tests on protected branches should skip the test cache,
+	// which helps spot test flakes and bugs hidden by the caching.
 	//
-	// Critically we only want to do this in the main repo, not the trybot
-	// repo.
-	//
-	// TODO(mvdan): rethink for Namespace, where trimming the cache size is irrelevant.
-	// A better approach there is likely to set GOFLAGS=-count=1 for "go test",
-	// assuming that does not interfere with other commands like "go vet",
-	// as -count=1 is the canonical way to disable test caching.
+	// Critically, we don't skip the test cache on the trybot repo,
+	// so that the testing of CLs can rely on an up to date test cache.
 	githubactions.#Step & {
 		if:  "github.repository == '\(githubRepositoryPath)' && (\(isProtectedBranch) || \(isTestDefaultBranch))"
-		run: "go clean -testcache"
+		run: "go env -w GOFLAGS=-count=1"
 	},
 ]