Change det_dataset_from_uri so it returns a Butler

Otherwise there is no easy way for the caller to get the
dataset:

butler, ref = Butler.get_dataset_from_uri(uri)
thing = butler.get(ref)

python/lsst/daf/butler/_butler.py

@@ -587,7 +587,7 @@ def parse_dataset_uri(cls, uri: str) -> tuple[str, DatasetId]:
     @classmethod
     def get_dataset_from_uri(
         cls, uri: str, factory: LabeledButlerFactoryProtocol | None = None
-    ) -> DatasetRef | None:
+    ) -> tuple[Butler, DatasetRef | None]:
         """Get the dataset associated with the given dataset URI.
 
         Parameters
@@ -596,10 +596,13 @@ def get_dataset_from_uri(
             The URI associated with a dataset.
         factory : `LabeledButlerFactoryProtocol` or `None`, optional
             Bound factory function that will be given the butler label
-            and receive a `Butler`.
+            and receive a `Butler`. If this is not provided the label
+            will be tried directly.
 
         Returns
         -------
+        butler : `Butler`
+            Butler object associated with this URI.
         ref : `DatasetRef` or `None`
             The dataset associated with that URI, or `None` if the UUID
             is valid but the dataset is not known to this butler.
@@ -614,7 +617,7 @@ def get_dataset_from_uri(
                 pass
         if butler is None:
             butler = cls.from_config(label)
-        return butler.get_dataset(dataset_id)
+        return butler, butler.get_dataset(dataset_id)
 
     @abstractmethod
     def _caching_context(self) -> AbstractContextManager[None]:

tests/test_simpleButler.py

@@ -917,15 +917,23 @@ def test_dataset_uris(self):
                     f"butler://{label}/{ref.id}",
                     f"ivo://rubin.lsst/datasets?{label}/{ref.id}",
                 ):
-                    ref2 = Butler.get_dataset_from_uri(dataset_uri)
+                    new_butler, ref2 = Butler.get_dataset_from_uri(dataset_uri)
                     self.assertEqual(ref, ref2)
+                    # The returned butler needs to have the datastore mocked.
+                    DatastoreMock.apply(new_butler)
+                    dataset_id, _ = butler.get(ref2)
+                    self.assertEqual(dataset_id, ref.id)
 
-                    ref2 = Butler.get_dataset_from_uri(dataset_uri, factory=factory)
+                    factory_butler, ref2 = Butler.get_dataset_from_uri(dataset_uri, factory=factory)
                     self.assertEqual(ref, ref2)
+                    # The returned butler needs to have the datastore mocked.
+                    DatastoreMock.apply(factory_butler)
+                    dataset_id, _ = factory_butler.get(ref2)
+                    self.assertEqual(dataset_id, ref.id)
 
                 # Non existent dataset.
                 missing_id = str(ref.id).replace("2", "3")
-                no_ref = Butler.get_dataset_from_uri(f"butler://{label}/{missing_id}")
+                _, no_ref = Butler.get_dataset_from_uri(f"butler://{label}/{missing_id}")
                 self.assertIsNone(no_ref)
 
         # Test some failure modes.