Isolate synthetic module downloads in workflow tests

cmd/releasekit/woodpecker_test.go

@@ -150,6 +150,19 @@ func TestWoodpeckerTagDeliveryTemplate(t *testing.T) {
 }
 
 func TestWoodpeckerTagDeliveryUsesTaggedModuleVersion(t *testing.T) {
+	// Synthetic downloads must leave the caller's module cache untouched.
+	callerCache := t.TempDir()
+	t.Setenv("GOMODCACHE", callerCache)
+	t.Cleanup(func() {
+		entries, err := os.ReadDir(callerCache)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if len(entries) != 0 {
+			t.Errorf("synthetic module downloads modified the caller's cache: %v", entries)
+		}
+	})
+
 	root := cliRepositoryRoot(t)
 	contents, err := os.ReadFile(filepath.Join(root, "examples", "woodpecker", "tag-delivery.yml"))
 	if err != nil {
@@ -185,7 +198,7 @@ func TestWoodpeckerTagDeliveryUsesTaggedModuleVersion(t *testing.T) {
 		moduleBefore := readWoodpeckerFixtureFile(t, filepath.Join(repository, "go.mod"))
 		commit := oldCommit
 		env := templateEnvironment(repository, commit, goDir, goLog)
-		env["GOPROXY"] = "file://" + filepath.ToSlash(proxy)
+		useSyntheticModuleProxy(t, env, "file://"+filepath.ToSlash(proxy))
 		sumLog := filepath.Join(t.TempDir(), "tool-only-sums")
 		env["RELEASEKIT_SUM_LOG"] = sumLog
 		output := runWoodpeckerBlock(t, command, repository, env)
@@ -207,7 +220,7 @@ func TestWoodpeckerTagDeliveryUsesTaggedModuleVersion(t *testing.T) {
 		commit := pushTaggedCLIRepository(t, repository)
 		moduleBefore := readWoodpeckerFixtureFile(t, filepath.Join(repository, "go.mod"))
 		env := templateEnvironment(repository, commit, goDir, goLog)
-		env["GOPROXY"] = "file://" + filepath.ToSlash(proxy)
+		useSyntheticModuleProxy(t, env, "file://"+filepath.ToSlash(proxy))
 		sumLog := filepath.Join(t.TempDir(), "tool-only-sums")
 		env["RELEASEKIT_SUM_LOG"] = sumLog
 		output := runWoodpeckerBlock(t, command, repository, env)
@@ -245,21 +258,15 @@ func TestWoodpeckerSourceDeliveryTemplateSelfBootstraps(t *testing.T) {
 	defer proxy.Close()
 	writeRepositoryFile(t, repository, "go.mod", "module example.com/cli-candidate\n\ngo 1.25.0\n\nrequire "+dependency+" v1.0.0\n")
 	writeRepositoryFile(t, repository, "cmd/releasekit/main.go", "package main\n\nimport (\"fmt\"; \"os\"; helper \""+dependency+"\")\n\nfunc main() {\n\tfmt.Println(\"self-bootstrap \" + helper.Message)\n\tfmt.Printf(\"tool-args=%q\\n\", os.Args[1:])\n}\n")
-	preparationEnv := map[string]string{
-		"GOPROXY": proxy.URL, "GOSUMDB": "off", "GONOPROXY": "none", "GOPRIVATE": "",
-		"GOWORK": "off", "GOTOOLCHAIN": "local", "GOENV": "off", "GOFLAGS": "-modcacherw",
-		"GOMODCACHE": t.TempDir(),
-	}
+	preparationEnv := map[string]string{}
+	useSyntheticModuleProxy(t, preparationEnv, proxy.URL)
 	runWoodpeckerBlock(t, "go mod download "+dependency, repository, preparationEnv)
 	cliGitRun(t, repository, "add", "cmd/releasekit/main.go", "go.mod", "go.sum")
 	cliGitRun(t, repository, "commit", "-m", "add the self-bootstrapped command")
 	commit := pushTaggedCLIRepository(t, repository)
 	goDir, goLog := installGoBootstrapShim(t)
 	env := templateEnvironment(repository, commit, goDir, goLog)
-	for key, value := range preparationEnv {
-		env[key] = value
-	}
-	env["GOMODCACHE"] = t.TempDir()
+	useSyntheticModuleProxy(t, env, proxy.URL)
 	proxyRequests.Store(0)
 	env["CI_COMMIT_SHA"] = strings.Repeat("0", len(commit))
 	if output, err := executeWoodpeckerBlock(command, repository, env); err == nil {
@@ -426,6 +433,19 @@ esac
 	return shimDir, goLog
 }
 
+func useSyntheticModuleProxy(t *testing.T, environment map[string]string, proxyURL string) {
+	t.Helper()
+	environment["GOMODCACHE"] = t.TempDir()
+	environment["GOPROXY"] = proxyURL
+	environment["GOSUMDB"] = "off"
+	environment["GONOPROXY"] = "none"
+	environment["GOPRIVATE"] = ""
+	environment["GOWORK"] = "off"
+	environment["GOTOOLCHAIN"] = "local"
+	environment["GOENV"] = "off"
+	environment["GOFLAGS"] = "-modcacherw"
+}
+
 func templateEnvironment(repository, commit, shimDir, goLog string) map[string]string {
 	realGo, _ := exec.LookPath("go")
 	return map[string]string{

docs/roadmap/promptkit-bug-report.md

@@ -1,7 +1,7 @@
 # PromptKit Bug Report: v0.2.0 Module Checksum Mismatch
 
-**Status:** Stale local module metadata confirmed; cache recovery and test
-isolation follow-up remain pending.
+**Status:** Stale local module metadata confirmed; test isolation fixed.
+Shared-cache recovery and PromptKit's adoption retry remain pending.
 
 ## Summary
 
@@ -95,22 +95,32 @@ Recovery was verified in a copied cache; PromptKit's adoption retry remains pend
 ### Related Test-Isolation Defect
 
 The workflow tests' [environment helper](../../cmd/releasekit/woodpecker_test.go)
-disables checksum verification for synthetic fixtures and inherits the caller's
+disabled checksum verification for synthetic fixtures and inherited the caller's
 module cache. The version-selection test serves synthetic ReleaseKit versions
 from a local module proxy.
 
 Running `TestWoodpeckerTagDeliveryUsesTaggedModuleVersion` with a disposable
 inherited `GOMODCACHE` passed and left synthetic `v0.2.197` and `v0.2.198`
-metadata in that cache. This confirms that the tests can contaminate a
-developer's module cache. It establishes a related defect; attribution of the
+metadata in that cache. This confirmed that the tests could contaminate a
+developer's module cache. It established a related defect; attribution of the
 stale `v0.2.0` entry to a particular test or command remains unconfirmed.
 
+### Test-Isolation Resolution
+
+Both synthetic-proxy test families now use a shared environment helper that
+assigns a fresh test-owned `GOMODCACHE` and scopes proxy/checksum settings to
+their Go subprocesses. Source-bootstrap preparation and execution retain
+separate caches. Tests that build real ReleaseKit source continue to use their
+prepared dependencies.
+
+The existing tagged-version test now supplies a disposable caller cache and
+asserts that it remains empty after fixture execution. This regression failed
+before the fix and passed afterward. All Woodpecker workflow tests passed.
+
 ## Recommended Follow-Up
 
 1. Quarantine the affected local `v0.2.0.mod` entry and retry PromptKit's adoption
    with normal checksum verification. Retain the quarantined bytes as evidence.
-2. Give synthetic module-proxy tests a temporary `GOMODCACHE` owned by the test
-   fixture, with focused regression coverage for cache isolation.
-3. Record the actual cache recovery and consumer retry outcomes here. Preserve
+2. Record the actual cache recovery and consumer retry outcomes here. Preserve
    the published v0.2.0 tag and checksums; this incident requires no replacement
    release.