fix: implement _exists for SharedMemoryDataset (#4121)

* fix: implement `_exists` for `SharedMemoryDataset`

Signed-off-by: Felix Scherz <felixwscherz@gmail.com>

* docs: updated RELEASE.md

Signed-off-by: Felix Scherz <felixwscherz@gmail.com>

* fix: ignore mypy warning on exists return type

Signed-off-by: Felix Scherz <felixwscherz@gmail.com>

---------

Signed-off-by: Felix Scherz <felixwscherz@gmail.com>
Signed-off-by: Ankita Katiyar <110245118+ankatiyar@users.noreply.github.com>
Co-authored-by: Ankita Katiyar <110245118+ankatiyar@users.noreply.github.com>

RELEASE.md

@@ -14,6 +14,7 @@
 * Enhanced `OmegaConfigLoader` configuration validation to detect duplicate keys at all parameter levels, ensuring comprehensive nested key checking.
 ## Bug fixes and other changes
 * Fixed bug where using dataset factories breaks with `ThreadRunner`.
+* Fixed a bug where `SharedMemoryDataset.exists` would not call the underlying `MemoryDataset`.
 * Fixed template projects example tests.
 * Made credentials loading consistent between `KedroContext._get_catalog()` and `resolve_patterns` so that both us
 e `_get_config_credentials()`
@@ -30,6 +31,7 @@ e `_get_config_credentials()`
 * [ethanknights](https://github.com/ethanknights)
 * [Manezki](https://github.com/Manezki)
 * [MigQ2](https://github.com/MigQ2)
+* [Felix Scherz](https://github.com/felixscherz)
 
 # Release 0.19.8
 

kedro/io/shared_memory_dataset.py

@@ -57,3 +57,8 @@ def save(self, data: Any) -> None:
     def _describe(self) -> dict[str, Any]:
         """SharedMemoryDataset doesn't have any constructor argument to return."""
         return {}
+
+    def _exists(self) -> bool:
+        if not self.shared_memory_dataset:
+            return False
+        return self.shared_memory_dataset.exists()  # type: ignore[no-any-return]

tests/io/test_shared_memory_dataset.py

@@ -79,3 +79,9 @@ def test_saving_none(self, shared_memory_dataset):
     def test_str_representation(self, shared_memory_dataset):
         """Test string representation of the dataset"""
         assert "MemoryDataset" in str(shared_memory_dataset)
+
+    def test_exists(self, shared_memory_dataset, input_data):
+        """Check that exists returns the expected values"""
+        assert not shared_memory_dataset.exists()
+        shared_memory_dataset.save(input_data)
+        assert shared_memory_dataset.exists()