Introduce a sentinel value _NO_VALUE to improve Global resolvers to support defaults 0 or None

kedro/config/omegaconf_config.py

@@ -20,6 +20,8 @@
 
 _config_logger = logging.getLogger(__name__)
 
+_NO_VALUE = object()
+
 
 class OmegaConfigLoader(AbstractConfigLoader):
     """Recursively scan directories (config paths) contained in ``conf_source`` for
@@ -316,31 +318,28 @@ def _register_globals_resolver(self):
         """Register the globals resolver"""
         OmegaConf.register_new_resolver(
             "globals",
-            lambda variable, default_value=None: self._get_globals_value(
-                variable, default_value
-            ),
+            self._get_globals_value,
             replace=True,
         )
 
-    def _get_globals_value(self, variable, default_value):
+    def _get_globals_value(self, variable, default_value=_NO_VALUE):
         """Return the globals values to the resolver"""
         if variable.startswith("_"):
             raise InterpolationResolutionError(
                 "Keys starting with '_' are not supported for globals."
             )
-        keys = variable.split(".")
-        value = self["globals"]
-        for k in keys:
-            value = value.get(k)
-            if not value:
-                if default_value:
-                    _config_logger.debug(
-                        f"Using the default value for the global variable {variable}."
-                    )
-                    return default_value
-                msg = f"Globals key '{variable}' not found and no default value provided. "
-                raise InterpolationResolutionError(msg)
-        return value
+        global_omegaconf = OmegaConf.create(self["globals"])
+        interpolated_value = OmegaConf.select(
+            global_omegaconf, variable, default=default_value
+        )
+        if interpolated_value != _NO_VALUE:
+            return interpolated_value
+        else:
+            raise InterpolationResolutionError(
+                "Default value is not defined for {$globals: {keys}}.".replace(
+                    "{keys}", variable
+                )
+            )
 
     @staticmethod
     def _register_new_resolvers(resolvers: dict[str, Callable]):

tests/config/test_omegaconf_config.py

@@ -676,7 +676,7 @@ def test_custom_resolvers(self, tmp_path):
     def test_globals(self, tmp_path):
         globals_params = tmp_path / _BASE_ENV / "globals.yml"
         globals_config = {
-            "x": 34,
+            "x": 0,
         }
         _write_yaml(globals_params, globals_config)
         conf = OmegaConfigLoader(tmp_path, default_run_env="")
@@ -704,7 +704,6 @@ def test_globals_resolution(self, tmp_path):
         _write_yaml(globals_params, globals_config)
         _write_yaml(base_catalog, catalog_config)
         conf = OmegaConfigLoader(tmp_path, default_run_env="")
-        assert OmegaConf.has_resolver("globals")
         # Globals are resolved correctly in parameter
         assert conf["parameters"]["my_param"] == globals_config["x"]
         # The default value is used if the key does not exist
@@ -760,25 +759,67 @@ def test_globals_across_env(self, tmp_path):
         # Base global value is accessible to local params
         assert conf["parameters"]["param2"] == base_globals_config["x"]
 
-    def test_bad_globals(self, tmp_path):
+    def test_globals_default(self, tmp_path):
+        base_params = tmp_path / _BASE_ENV / "parameters.yml"
+        base_globals = tmp_path / _BASE_ENV / "globals.yml"
+        base_param_config = {
+            "int": "${globals:x.NOT_EXIST, 1}",
+            "str": "${globals: x.NOT_EXIST, '2'}",
+            "dummy": "${globals: x.DUMMY.DUMMY, '2'}",
+        }
+        base_globals_config = {"x": {"DUMMY": 3}}
+        _write_yaml(base_params, base_param_config)
+        _write_yaml(base_globals, base_globals_config)
+        conf = OmegaConfigLoader(tmp_path, default_run_env="")
+        # Default value is being used as int
+        assert conf["parameters"]["int"] == 1
+        # Default value is being used as str
+        assert conf["parameters"]["str"] == "2"
+        # Test when x.DUMMY is not a dictionary it should still work
+        assert conf["parameters"]["dummy"] == "2"
+
+    def test_globals_default_none(self, tmp_path):
         base_params = tmp_path / _BASE_ENV / "parameters.yml"
         base_globals = tmp_path / _BASE_ENV / "globals.yml"
         base_param_config = {
-            "param1": "${globals:x.y}",
+            "zero": "${globals: x.NOT_EXIST, 0}",
+            "null": "${globals: x.NOT_EXIST, null}",
+            "null2": "${globals: x.y}",
         }
         base_globals_config = {
             "x": {
                 "z": 23,
+                "y": None,
             },
         }
         _write_yaml(base_params, base_param_config)
         _write_yaml(base_globals, base_globals_config)
         conf = OmegaConfigLoader(tmp_path, default_run_env="")
+        # Default value can be 0 or null
+        assert conf["parameters"]["zero"] == 0
+        assert conf["parameters"]["null"] is None
+        # Global value is null
+        assert conf["parameters"]["null2"] is None
+
+    def test_globals_missing_default(self, tmp_path):
+        base_params = tmp_path / _BASE_ENV / "parameters.yml"
+        globals_params = tmp_path / _BASE_ENV / "globals.yml"
+        param_config = {
+            "NOT_OK": "${globals:nested.NOT_EXIST}",
+        }
+        globals_config = {
+            "nested": {
+                "y": 42,
+            },
+        }
+        _write_yaml(base_params, param_config)
+        _write_yaml(globals_params, globals_config)
+        conf = OmegaConfigLoader(tmp_path, default_run_env="")
+
         with pytest.raises(
-            InterpolationResolutionError,
-            match=r"Globals key 'x.y' not found and no default value provided.",
+            InterpolationResolutionError, match="Default value is not defined for"
         ):
-            conf["parameters"]["param1"]
+            conf["parameters"]["NOT_OK"]
 
     def test_bad_globals_underscore(self, tmp_path):
         base_params = tmp_path / _BASE_ENV / "parameters.yml"