zulip-puppet-apply: Factor out the --noop returncode logic.

scripts/zulip-puppet-apply

@@ -6,6 +6,7 @@ import re
 import subprocess
 import sys
 import tempfile
+from typing import List
 
 import yaml
 
@@ -68,22 +69,30 @@ if (distro_info["ID"], distro_info["VERSION_ID"]) in [("ubuntu", "20.04")]:
 if (distro_info["ID"], distro_info["VERSION_ID"]) in [("ubuntu", "22.04")]:
     puppet_env["RUBYOPT"] = "-r " + os.path.join(scripts_path, "lib", "ruby3hack.rb")
 
-if not args.noop and not args.force:
-    # --noop does not work with --detailed-exitcodes; see https://tickets.puppetlabs.com/browse/PUP-686
+
+def noop_would_change(puppet_cmd: List[str]) -> bool:
+    # --noop does not work with --detailed-exitcodes; see
+    # https://tickets.puppetlabs.com/browse/PUP-686
     try:
         lastrun_file = tempfile.NamedTemporaryFile()
         subprocess.check_call(
-            [*puppet_cmd, "--noop", "--show_diff", "--lastrunfile", lastrun_file.name],
+            # puppet_cmd may already contain --noop, but it is safe to
+            # supply twice
+            [*puppet_cmd, "--noop", "--lastrunfile", lastrun_file.name],
             env=puppet_env,
         )
 
         with open(lastrun_file.name) as lastrun:
             lastrun_data = yaml.safe_load(lastrun)
-            if lastrun_data.get("resources", {}).get("out_of_sync", 0) == 0:
-                sys.exit(0)
+            return lastrun_data.get("resources", {}).get("out_of_sync", 0) != 0
     finally:
         lastrun_file.close()
 
+
+if not args.noop and not args.force:
+    if not noop_would_change([*puppet_cmd, "--show_diff"]):
+        sys.exit(0)
+
     do_apply = None
     while do_apply != "y":
         sys.stdout.write("Apply changes? [y/N] ")