Option to error on missing Jinja2 variables (#27)

This allows a user to specify if they want to allow missing variables in a jinja2 template. If allow_missing == False, a NameError will be raised with the name of the variable that is undefined. The default is True, which is the current behavior.

src/wxflow/jinja.py

@@ -225,7 +225,7 @@ def _render_template(self, template: jinja2.Template) -> str:
         try:
             rendered = template.render(**self.data)
         except jinja2.UndefinedError as ee:
-            raise Exception(f"Undefined variable in Jinja2 template\n{ee}")
+            raise NameError(f"Undefined variable in Jinja2 template\n{ee}")
 
         return rendered
 

src/wxflow/yaml_file.py

@@ -156,7 +156,7 @@ def vanilla_yaml(ctx):
         return ctx
 
 
-def parse_j2yaml(path: str, data: Dict, searchpath: Union[str, List] = '/') -> Dict[str, Any]:
+def parse_j2yaml(path: str, data: Dict, searchpath: Union[str, List] = '/', allow_missing: bool = True) -> Dict[str, Any]:
     """
     Description
     -----------
@@ -171,6 +171,8 @@ def parse_j2yaml(path: str, data: Dict, searchpath: Union[str, List] = '/') -> D
         the context for jinja2 templating
     searchpath: str | List
         additional search paths for included jinja2 templates
+    allow_missing: bool
+        whether to allow missing variables in a jinja2 template or not
     Returns
     -------
     Dict[str, Any]
@@ -180,4 +182,4 @@ def parse_j2yaml(path: str, data: Dict, searchpath: Union[str, List] = '/') -> D
     if not os.path.exists(path):
         raise FileNotFoundError(f"Input j2yaml file {path} does not exist!")
 
-    return YAMLFile(data=Jinja(path, data, searchpath=searchpath).render)
+    return YAMLFile(data=Jinja(path, data, searchpath=searchpath, allow_missing=allow_missing).render)

tests/test_yaml_file.py

@@ -53,6 +53,15 @@ def test_yaml_file(tmp_path, create_template):
     assert yaml_in == conf
 
 
+def test_j2template_missing_var(tmp_path, create_template):
+
+    # Try to parse a j2yaml with an undefined variable (user)
+    os.environ['TMP_PATH'] = str(tmp_path)
+    with pytest.raises(NameError) as e_info:
+        data = {'current_cycle': datetime.now()}
+        conf = parse_j2yaml(path=str(tmp_path / 'j2tmpl.yaml'), data=data, allow_missing=False)
+
+
 def test_yaml_file_with_j2templates(tmp_path, create_template):
 
     # Set env. variable