Users can set BAZELISK_SHUTDOWN to run bazel shutdown during testing …

…incompatible flags (bazelbuild#85)

README.md

@@ -53,6 +53,9 @@ show you which flags can safely enabled, and which flags require a migration.
 You can set `BAZELISK_GITHUB_TOKEN` to set a GitHub access token to use for API
 requests to avoid rate limiting when on shared networks.
 
+You can set `BAZELISK_SHUTDOWN` to run `shutdown` between builds when
+migrating if you suspect this affects your results.
+
 You can set `BAZELISK_CLEAN` to run `clean --expunge` between builds when
 migrating if you suspect this affects your results.
 

bazelisk.go

@@ -541,13 +541,33 @@ func insertArgs(baseArgs []string, newArgs []string) []string {
 	return result
 }
 
+func shutdownIfNeeded(bazelPath string) {
+	bazeliskClean := os.Getenv("BAZELISK_SHUTDOWN")
+	if len(bazeliskClean) == 0 {
+		return
+	}
+
+	fmt.Printf("bazel shutdown\n")
+	exitCode, err := runBazel(bazelPath, []string{"shutdown"})
+	fmt.Printf("\n")
+	if err != nil {
+		log.Fatalf("failed to run bazel shutdown: %v", err)
+	}
+	if exitCode != 0 {
+		fmt.Printf("Failure: shutdown command failed.\n")
+		os.Exit(exitCode)
+	}
+}
+
 func cleanIfNeeded(bazelPath string) {
 	bazeliskClean := os.Getenv("BAZELISK_CLEAN")
 	if len(bazeliskClean) == 0 {
 		return
 	}
 
+	fmt.Printf("bazel clean --expunge\n")
 	exitCode, err := runBazel(bazelPath, []string{"clean", "--expunge"})
+	fmt.Printf("\n")
 	if err != nil {
 		log.Fatalf("failed to run clean: %v", err)
 	}
@@ -562,8 +582,9 @@ func migrate(bazelPath string, baseArgs []string, newArgs []string) {
 	// 1. Try with all the flags.
 	args := insertArgs(baseArgs, newArgs)
 	fmt.Printf("\n\n--- Running Bazel with all incompatible flags\n\n")
-	fmt.Printf("bazel %s\n", strings.Join(args, " "))
+	shutdownIfNeeded(bazelPath)
 	cleanIfNeeded(bazelPath)
+	fmt.Printf("bazel %s\n", strings.Join(args, " "))
 	exitCode, err := runBazel(bazelPath, args)
 	if err != nil {
 		log.Fatalf("could not run Bazel: %v", err)
@@ -576,8 +597,9 @@ func migrate(bazelPath string, baseArgs []string, newArgs []string) {
 	// 2. Try with no flags, as a sanity check.
 	args = baseArgs
 	fmt.Printf("\n\n--- Running Bazel with no incompatible flags\n\n")
-	fmt.Printf("bazel %s\n", strings.Join(args, " "))
+	shutdownIfNeeded(bazelPath)
 	cleanIfNeeded(bazelPath)
+	fmt.Printf("bazel %s\n", strings.Join(args, " "))
 	exitCode, err = runBazel(bazelPath, args)
 	if err != nil {
 		log.Fatalf("could not run Bazel: %v", err)
@@ -593,8 +615,9 @@ func migrate(bazelPath string, baseArgs []string, newArgs []string) {
 	for _, arg := range newArgs {
 		args = insertArgs(baseArgs, []string{arg})
 		fmt.Printf("\n\n--- Running Bazel with %s\n\n", arg)
-		fmt.Printf("bazel %s\n", strings.Join(args, " "))
+		shutdownIfNeeded(bazelPath)
 		cleanIfNeeded(bazelPath)
+		fmt.Printf("bazel %s\n", strings.Join(args, " "))
 		exitCode, err = runBazel(bazelPath, args)
 		if err != nil {
 			log.Fatalf("could not run Bazel: %v", err)