Properly fix tests for bad vasprun dielectric.

src/pymatgen/io/vasp/outputs.py

@@ -486,7 +486,8 @@ def _parse(
                                 label = "velocity"
                             else:
                                 warnings.warn(
-                                    "Additional unlabelled dielectric data in vasprun.xml are stored as unlabelled."
+                                    "Additional unlabelled dielectric data in vasprun.xml are stored as unlabelled.",
+                                    UserWarning,
                                 )
                                 label = "unlabelled"
                         # VASP 6+ has labels for the density and current
@@ -1522,16 +1523,18 @@ def _parse_structure(self, elem: XML_Element) -> Structure:
     @staticmethod
     def _parse_diel(elem: XML_Element) -> tuple[list, list, list]:
         """Parse dielectric properties."""
-        imag = [
-            [_vasprun_float(line) for line in r.text.split()]  # type: ignore[union-attr]
-            for r in elem.find("imag").find("array").find("set").findall("r")  # type: ignore[union-attr]
-        ]
-        real = [
-            [_vasprun_float(line) for line in r.text.split()]  # type: ignore[union-attr]
-            for r in elem.find("real").find("array").find("set").findall("r")  # type: ignore[union-attr]
-        ]
-        elem.clear()
-        return [e[0] for e in imag], [e[1:] for e in real], [e[1:] for e in imag]
+        if elem.find("real") and elem.find("imag"):
+            imag = [
+                [_vasprun_float(line) for line in r.text.split()]  # type: ignore[union-attr]
+                for r in elem.find("imag").find("array").find("set").findall("r")  # type: ignore[union-attr]
+            ]
+            real = [
+                [_vasprun_float(line) for line in r.text.split()]  # type: ignore[union-attr]
+                for r in elem.find("real").find("array").find("set").findall("r")  # type: ignore[union-attr]
+            ]
+            elem.clear()
+            return [e[0] for e in imag], [e[1:] for e in real], [e[1:] for e in imag]
+        return [], [], []
 
     @staticmethod
     def _parse_optical_transition(elem: XML_Element) -> tuple[NDArray, NDArray]:

tests/io/vasp/test_outputs.py

@@ -122,11 +122,12 @@ def test_BSE(self):
         assert "freq_dependent" in vasp_run.dielectric_data
 
     def test_vasprun_with_more_than_two_unlabelled_dielectric_functions(self):
-        with pytest.raises(
-            NotImplementedError,
-            match="This vasprun.xml has >2 unlabelled dielectric functions",
+        with pytest.warns(
+            UserWarning,
+            match="Additional unlabelled dielectric data in vasprun.xml are stored as unlabelled.",
         ):
-            Vasprun(f"{VASP_OUT_DIR}/vasprun.dielectric_bad.xml.gz")
+            vr = Vasprun(f"{VASP_OUT_DIR}/vasprun.dielectric_bad.xml.gz")
+            assert "unlabelled" in vr.dielectric_data
 
     def test_bad_vasprun(self):
         with pytest.raises(ET.ParseError):