From 14d51e0ebaa4de3f122ec85478002d559245fabc Mon Sep 17 00:00:00 2001
From: Jonathan Shimwell <mail@jshimwell.com>
Date: Thu, 14 Aug 2025 20:26:27 +0200
Subject: [PATCH] more helpful error message for dose_coefficients (#3534)

---
 openmc/data/effective_dose/dose.py |  7 ++++++-
 tests/unit_tests/test_data_dose.py | 20 ++++++++++++++++++++
 2 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/openmc/data/effective_dose/dose.py b/openmc/data/effective_dose/dose.py
index c7f458d1c6..d49043b0a6 100644
--- a/openmc/data/effective_dose/dose.py
+++ b/openmc/data/effective_dose/dose.py
@@ -82,7 +82,12 @@ def dose_coefficients(particle, geometry='AP', data_source='icrp116'):
     cv.check_value('data_source', data_source, {'icrp74', 'icrp116'})
 
     if (data_source, particle) not in _FILES:
-        raise ValueError(f"{particle} has no dose data in data source {data_source}.")
+        available_particles = sorted({p for (ds, p) in _FILES if ds == data_source})
+        msg = (
+            f"'{particle}' has no dose data in data source {data_source}. "
+            f"Available particles for {data_source} are: {available_particles}"
+        )
+        raise ValueError(msg)
     elif (data_source, particle) not in _DOSE_TABLES:
         _load_dose_icrp(data_source, particle)
 
diff --git a/tests/unit_tests/test_data_dose.py b/tests/unit_tests/test_data_dose.py
index 2d80cf8384..4f18800143 100644
--- a/tests/unit_tests/test_data_dose.py
+++ b/tests/unit_tests/test_data_dose.py
@@ -41,3 +41,23 @@ def test_dose_coefficients():
         dose_coefficients('neutron', 'ZZ')
     with raises(ValueError):
         dose_coefficients('neutron', data_source='icrp7000')
+    with raises(ValueError) as excinfo:
+        dose_coefficients("photons", data_source="icrp116")
+    expected_particles = [
+        "electron",
+        "helium",
+        "mu+",
+        "mu-",
+        "neutron",
+        "photon",
+        "photon kerma",
+        "pi+",
+        "pi-",
+        "positron",
+        "proton",
+    ]
+    expected_msg = (
+        "'photons' has no dose data in data source icrp116. "
+        f"Available particles for icrp116 are: {expected_particles}"
+    )
+    assert str(excinfo.value) == expected_msg