Bug fix for parse dataest definition (#3400)

* add tests to test definitio explicitly

Signed-off-by: Nok <nok.lam.chan@quantumblack.com>

* fix tests

Signed-off-by: Nok <nok.lam.chan@quantumblack.com>

* update docstring

Signed-off-by: Nok <nok.lam.chan@quantumblack.com>

---------

Signed-off-by: Nok <nok.lam.chan@quantumblack.com>

kedro/io/core.py

@@ -357,7 +357,7 @@ def parse_dataset_definition(
 
     Args:
         config: Data set config dictionary. It *must* contain the `type` key
-            with fully qualified class name.
+            with fully qualified class name or the class object.
         load_version: Version string to be used for ``load`` operation if
             the data set is versioned. Has no effect on the data set
             if versioning was not enabled.
@@ -378,6 +378,7 @@ def parse_dataset_definition(
         raise DatasetError("'type' is missing from dataset catalog configuration")
 
     dataset_type = config.pop("type")
+    class_obj = None
     if isinstance(dataset_type, str):
         if len(dataset_type.strip(".")) != len(dataset_type):
             raise DatasetError(
@@ -394,6 +395,9 @@ def parse_dataset_definition(
         else:
             raise DatasetError(f"Class '{dataset_type}' not found, is this a typo?")
 
+    if not class_obj:
+        class_obj = dataset_type
+
     if not issubclass(class_obj, AbstractDataset):
         raise DatasetError(
             f"Dataset type '{class_obj.__module__}.{class_obj.__qualname__}' "

tests/io/test_core.py

@@ -22,6 +22,7 @@
     parse_dataset_definition,
     validate_on_forbidden_chars,
 )
+from kedro.io.lambda_dataset import LambdaDataset
 
 # List sourced from https://docs.python.org/3/library/stdtypes.html#truth-value-testing.
 # Excludes None, as None values are not shown in the str representation.
@@ -292,6 +293,15 @@ def side_effect_function(value):
         with pytest.raises(DatasetError, match=pattern):
             parse_dataset_definition({"type": dataset_name})
 
+    def test_parse_dataset_definition(self):
+        config = {"type": "LambdaDataset"}
+        dataset, _ = parse_dataset_definition(config)
+        assert dataset is LambdaDataset
+
+    def test_test_parse_dataset_definition_with_python_class_type(self):
+        config = {"type": MyDataset}
+        parse_dataset_definition(config)
+
 
 class TestAbstractVersionedDataset:
     def test_version_str_repr(self, load_version, save_version):