Add public config_file attribute to Config classes

src/uwtools/config/formats/base.py

@@ -210,6 +210,13 @@ def compare_config(
             log.info(diffline.rstrip())
         return False
 
+    @property
+    def config_file(self) -> Optional[Path]:
+        """
+        Return the path to the config file from which this object was instantiated, if applicable.
+        """
+        return self._config_file
+
     def dereference(self, context: Optional[dict] = None) -> None:
         """
         Render as much Jinja2 syntax as possible.

src/uwtools/tests/config/formats/test_base.py

@@ -194,6 +194,11 @@ def test_compare_config_ini(caplog, salad_base):
         assert not logged(caplog, line)
 
 
+def test_config_file(config):
+    assert config.config_file.name == "config.yaml"
+    assert config.config_file.is_file()
+
+
 def test_dereference(tmp_path):
     # Test demonstrates that:
     #   - Config dereferencing ignores environment variables.