From 706074b035f82eff0bd1bc758bb402dd01d44956 Mon Sep 17 00:00:00 2001
From: Edoardo Zoni <ezoni@lbl.gov>
Date: Mon, 27 Apr 2026 13:38:23 -0700
Subject: [PATCH] Fix silent failure in analysis_default_regression.py

---
 Examples/analysis_default_regression.py | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/Examples/analysis_default_regression.py b/Examples/analysis_default_regression.py
index 00cc4e31536..27a12d92cf2 100755
--- a/Examples/analysis_default_regression.py
+++ b/Examples/analysis_default_regression.py
@@ -32,12 +32,14 @@ def main(args):
 if __name__ == "__main__":
     # define parser
     parser = argparse.ArgumentParser()
+
     # add arguments: output path
     parser.add_argument(
         "--path",
         help="path to output file(s)",
         type=str,
     )
+
     # add arguments: relative tolerance
     # Identify whether the test is a restart test,
     # if it is, use a 1e-12 tolerance for the restart checksum analysis
@@ -50,6 +52,7 @@ def main(args):
         required=False,
         default=default_tolerance,
     )
+
     # add arguments: skip fields
     parser.add_argument(
         "--skip-fields",
@@ -57,6 +60,7 @@ def main(args):
         action="store_true",
         dest="skip_fields",
     )
+
     # add arguments: skip particles
     parser.add_argument(
         "--skip-particles",
@@ -64,23 +68,31 @@ def main(args):
         action="store_true",
         dest="skip_particles",
     )
+
     # parse arguments
     args = parser.parse_args()
+
     # set args.format automatically
+    args.format = None  # default
     try:
         yt.load(args.path)
     except Exception:
         try:
             OpenPMDTimeSeries(args.path)
         except Exception:
-            print("Could not open the file as a plotfile or an openPMD time series")
+            pass  # neither format matched
         else:
             args.format = "openpmd"
     else:
         args.format = "plotfile"
+    if args.format is None:
+        raise ValueError(f"Could not detect format for path: {args.path}")
+
     # set args.do_fields (not parsed, based on args.skip_fields)
     args.do_fields = False if args.skip_fields else True
+
     # set args.do_particles (not parsed, based on args.skip_particles)
     args.do_particles = False if args.skip_particles else True
+
     # execute main function
     main(args)