data_models: handle SyntaxError and ImportError for custom themes

rendercv/data_models.py

@@ -1014,7 +1014,7 @@ class RenderCVDataModel(RenderCVBaseModel):
 
             if path_to_init_file.exists():
                 spec = importlib.util.spec_from_file_location(
-                    "",  # this is somehow not required
+                    "theme",
                     path_to_init_file,
                 )
                 if spec is None:
@@ -1024,7 +1024,13 @@ class RenderCVDataModel(RenderCVBaseModel):
                     )
 
                 theme_module = importlib.util.module_from_spec(spec)
-                spec.loader.exec_module(theme_module)  # type: ignore
+                try:
+                    spec.loader.exec_module(theme_module)  # type: ignore
+                except SyntaxError or ImportError:
+                    raise ValueError(
+                        f"The custom theme {theme_name}'s __init__.py file is not"
+                        " valid. Please check the file and try again.",
+                    )
 
                 ThemeDataModel = getattr(
                     theme_module, f"{theme_name.title()}ThemeOptions"  # type: ignore

tests/test_data_models.py

@@ -514,3 +514,28 @@ def test_custom_theme_without_init_file(tmp_path, testdata_directory_path):
     )
 
     assert data_model.design.theme == "dummytheme"
+
+
+def test_custom_theme_with_broken_init_file(tmp_path, testdata_directory_path):
+    reference_custom_theme_path = (
+        testdata_directory_path
+        / "test_copy_theme_files_to_output_directory_custom_theme"
+        / "dummytheme"
+    )
+
+    # copy the directory to tmp_path:
+    custom_theme_path = tmp_path / "dummytheme"
+    shutil.copytree(reference_custom_theme_path, custom_theme_path, dirs_exist_ok=True)
+
+    # remove the __init__.py file:
+    init_file = custom_theme_path / "__init__.py"
+    init_file.write_text("invalid python code", encoding="utf-8")
+
+    os.chdir(tmp_path)
+    with pytest.raises(pydantic.ValidationError):
+        dm.RenderCVDataModel(
+            **{  # type: ignore
+                "cv": {"name": "John Doe"},
+                "design": {"theme": "dummytheme"},
+            }
+        )