Add useful warning message for empty files

src/simweights/_corsika_weighter.py

@@ -55,6 +55,10 @@ def sframe_corsika_surface(table: Any) -> GenerationSurface:
 def weight_map_corsika_surface(table: Any) -> GenerationSurface:
     """Inspect the `CorsikaWeightMap` table object of a corsika file to generate a surface object."""
     pdgids = sorted(np.unique(get_column(table, "ParticleType").astype(int)))
+
+    if len(pdgids) == 0:
+        msg = "`CorsikaWeightMap` is empty. SimWeights cannot process this file"
+        raise RuntimeError(msg)
     surface: int | GenerationSurface = 0
     for pdgid in pdgids:
         mask = pdgid == get_column(table, "ParticleType")

src/simweights/_nugen_weighter.py

@@ -53,10 +53,14 @@ def nugen_spectrum(table: Any) -> PowerLaw:
 
 def nugen_surface(table: Any) -> GenerationSurface:
     """Inspect the `I3MCWeightDict` table object of a nugen file to generate a surface object."""
-    spatial = nugen_spatial(table)
-    spectrum = nugen_spectrum(table)
     pdgid = get_column(table, "PrimaryNeutrinoType")
     unique_pdgids = np.unique(pdgid)
+    if len(unique_pdgids) == 0:
+        msg = "`I3MCWeightDict` is empty. SimWeights cannot process this file"
+        raise RuntimeError(msg)
+
+    spatial = nugen_spatial(table)
+    spectrum = nugen_spectrum(table)
 
     surfaces = []
     for pid in unique_pdgids:

tests/test_corsika_weighter.py

@@ -102,6 +102,10 @@ def test_old_corsika(self):
         with self.assertRaises(TypeError):
             CorsikaWeighter(d, nfiles=object())
 
+        with self.assertRaises(RuntimeError):
+            x = {"CorsikaWeightMap": {"ParticleType": []}, "PolyplopiaPrimary": {}}
+            CorsikaWeighter(x, nfiles=1)
+
     def test_sframe_corsika(self):
         c1 = simweights.NaturalRateCylinder(1200, 600, 0, 1)
         p1 = simweights.PowerLaw(0, 1e3, 1e4)

tests/test_nugen_weighter.py

@@ -109,6 +109,11 @@ def test_nugen_energy_pre_V04_00(self):
                     Ewidth = np.ediff1d(x)
                     np.testing.assert_allclose(y, 2 * weight * flux * Ewidth * c1.etendue / nfiles, 6e-3)
 
+    def test_empty(self):
+        with self.assertRaises(RuntimeError):
+            x = {"I3MCWeightDict": {"PrimaryNeutrinoType": []}}
+            NuGenWeighter(x, nfiles=1)
+
 
 if __name__ == "__main__":
     unittest.main()