Add a GroupNotFoundError (#3066)

dstansby · web-flow · commit af55fcfaefa4 · 2025-05-29T09:06:43.000Z
* Add a GroupNotFoundError

* Fixup tests

* Add changelog entries

* Remove inheritance change
diff --git a/changes/3066.feature.rst b/changes/3066.feature.rst
@@ -0,0 +1 @@
+Added `~zarr.errors.GroupNotFoundError`, which is raised when attempting to open a group that does not exist.
diff --git a/src/zarr/api/asynchronous.py b/src/zarr/api/asynchronous.py
@@ -39,7 +39,7 @@
 )
 from zarr.core.metadata import ArrayMetadataDict, ArrayV2Metadata, ArrayV3Metadata
 from zarr.core.metadata.v2 import _default_compressor, _default_filters
-from zarr.errors import NodeTypeValidationError
+from zarr.errors import GroupNotFoundError, NodeTypeValidationError
 from zarr.storage._common import make_store_path
 
 if TYPE_CHECKING:
@@ -836,7 +836,7 @@ async def open_group(
             overwrite=overwrite,
             attributes=attributes,
         )
-    raise FileNotFoundError(f"Unable to find group: {store_path}")
+    raise GroupNotFoundError(store, store_path.path)
 
 
 async def create(
diff --git a/src/zarr/errors.py b/src/zarr/errors.py
@@ -21,6 +21,14 @@ def __init__(self, *args: Any) -> None:
         super().__init__(self._msg.format(*args))
 
 
+class GroupNotFoundError(BaseZarrError, FileNotFoundError):
+    """
+    Raised when a group isn't found at a certain path.
+    """
+
+    _msg = "No group found in store {!r} at path {!r}"
+
+
 class ContainsGroupError(BaseZarrError):
     """Raised when a group already exists at a certain path."""
 
diff --git a/tests/test_metadata/test_v3.py b/tests/test_metadata/test_v3.py
@@ -20,7 +20,7 @@
     parse_fill_value,
     parse_zarr_format,
 )
-from zarr.errors import MetadataValidationError
+from zarr.errors import MetadataValidationError, NodeTypeValidationError
 
 if TYPE_CHECKING:
     from collections.abc import Sequence
@@ -62,7 +62,8 @@
 @pytest.mark.parametrize("data", [None, 1, 2, 4, 5, "3"])
 def test_parse_zarr_format_invalid(data: Any) -> None:
     with pytest.raises(
-        ValueError, match=f"Invalid value for 'zarr_format'. Expected '3'. Got '{data}'."
+        MetadataValidationError,
+        match=f"Invalid value for 'zarr_format'. Expected '3'. Got '{data}'.",
     ):
         parse_zarr_format(data)
 
@@ -88,7 +89,8 @@ def test_parse_node_type_invalid(node_type: Any) -> None:
 @pytest.mark.parametrize("data", [None, "group"])
 def test_parse_node_type_array_invalid(data: Any) -> None:
     with pytest.raises(
-        ValueError, match=f"Invalid value for 'node_type'. Expected 'array'. Got '{data}'."
+        NodeTypeValidationError,
+        match=f"Invalid value for 'node_type'. Expected 'array'. Got '{data}'.",
     ):
         parse_node_type_array(data)
 

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1 @@`
	`1`	+Added `~zarr.errors.GroupNotFoundError`, which is raised when attempting to open a group that does not exist.
Original file line number	Diff line number	Diff line change
`@@ -39,7 +39,7 @@`
`39`	`39`	`)`
`40`	`40`	`from zarr.core.metadata import ArrayMetadataDict, ArrayV2Metadata, ArrayV3Metadata`
`41`	`41`	`from zarr.core.metadata.v2 import _default_compressor, _default_filters`
`42`		`-from zarr.errors import NodeTypeValidationError`
	`42`	`+from zarr.errors import GroupNotFoundError, NodeTypeValidationError`
`43`	`43`	`from zarr.storage._common import make_store_path`
`44`	`44`
`45`	`45`	`if TYPE_CHECKING:`
`@@ -836,7 +836,7 @@ async def open_group(`
`836`	`836`	`overwrite=overwrite,`
`837`	`837`	`attributes=attributes,`
`838`	`838`	`)`
`839`		`- raise FileNotFoundError(f"Unable to find group: {store_path}")`
	`839`	`+ raise GroupNotFoundError(store, store_path.path)`
`840`	`840`
`841`	`841`
`842`	`842`	`async def create(`