Add RemoteButler.find_dataset and corresponding server implementation

This is not the final interface for client/server but is there
to have something in place.

python/lsst/daf/butler/remote_butler/_remote_butler.py

@@ -40,18 +40,20 @@
 from .._butler_config import ButlerConfig
 from .._config import Config
 from .._dataset_existence import DatasetExistence
-from .._dataset_ref import DatasetIdGenEnum, DatasetRef
+from .._dataset_ref import DatasetIdGenEnum, DatasetRef, SerializedDatasetRef
 from .._dataset_type import DatasetType, SerializedDatasetType
 from .._deferredDatasetHandle import DeferredDatasetHandle
 from .._file_dataset import FileDataset
 from .._limited_butler import LimitedButler
 from .._storage_class import StorageClass
 from .._timespan import Timespan
 from ..datastore import DatasetRefURIs
-from ..dimensions import DataId, DimensionConfig, DimensionUniverse
-from ..registry import CollectionArgType, Registry, RegistryDefaults
+from ..dimensions import DataCoordinate, DataId, DimensionConfig, DimensionUniverse, SerializedDataCoordinate
+from ..registry import CollectionArgType, NoDefaultCollectionError, Registry, RegistryDefaults
+from ..registry.wildcards import CollectionWildcard
 from ..transfers import RepoExportContext
 from ._config import RemoteButlerConfigModel
+from .server import FindDatasetModel
 
 
 class RemoteButler(Butler):
@@ -101,6 +103,36 @@ def dimensions(self) -> DimensionUniverse:
         self._dimensions = DimensionUniverse(config)
         return self._dimensions
 
+    def _simplify_dataId(
+        self, dataId: DataId | None, **kwargs: dict[str, int | str]
+    ) -> SerializedDataCoordinate | None:
+        """Take a generic Data ID and convert it to a serializable form.
+
+        Parameters
+        ----------
+        dataId : `dict`, `None`, `DataCoordinate`
+            The data ID to serialize.
+        **kwargs : `dict`
+            Additional values that should be included if this is not
+            a `DataCoordinate`.
+
+        Returns
+        -------
+        data_id : `SerializedDataCoordinate` or `None`
+            A serializable form.
+        """
+        if dataId is None and not kwargs:
+            return None
+        if isinstance(dataId, DataCoordinate):
+            return dataId.to_simple()
+
+        if dataId is None:
+            dataId = kwargs
+        elif kwargs:
+            dataId.update(kwargs)
+        # Assume we can treat it as a dict.
+        return SerializedDataCoordinate(dataId=dataId)
+
     def getDatasetType(self, name: str) -> DatasetType:
         # Docstring inherited.
         raise NotImplementedError()
@@ -196,7 +228,31 @@ def find_dataset(
         datastore_records: bool = False,
         **kwargs: Any,
     ) -> DatasetRef | None:
-        raise NotImplementedError()
+        if collections is None:
+            if not self.collections:
+                raise NoDefaultCollectionError(
+                    "No collections provided to find_dataset, and no defaults from butler construction."
+                )
+            collections = self.collections
+        # Temporary hack. Assume strings for collections. In future
+        # want to construct CollectionWildcard and filter it through collection
+        # cache to generate list of collection names.
+        wildcards = CollectionWildcard.from_expression(collections)
+
+        if isinstance(datasetType, DatasetType):
+            datasetType = DatasetType.name
+
+        query = FindDatasetModel(
+            dataId=self._simplify_dataId(dataId, **kwargs), collections=wildcards.strings
+        )
+
+        path = f"find_dataset/{datasetType}"
+        response = self._client.post(
+            self._get_url(path), json=query.model_dump(mode="json", exclude_unset=True)
+        )
+        response.raise_for_status()
+
+        return DatasetRef.from_simple(SerializedDatasetRef(**response.json()), universe=self.dimensions)
 
     def retrieveArtifacts(
         self,

python/lsst/daf/butler/remote_butler/server/__init__.py

@@ -27,3 +27,4 @@
 
 from ._factory import *
 from ._server import *
+from ._server_models import *

python/lsst/daf/butler/remote_butler/server/_server.py

@@ -35,9 +35,16 @@
 
 from fastapi import Depends, FastAPI
 from fastapi.middleware.gzip import GZipMiddleware
-from lsst.daf.butler import Butler, SerializedDatasetType
+from lsst.daf.butler import (
+    Butler,
+    DataCoordinate,
+    SerializedDataCoordinate,
+    SerializedDatasetRef,
+    SerializedDatasetType,
+)
 
 from ._factory import Factory
+from ._server_models import FindDatasetModel
 
 BUTLER_ROOT = "ci_hsc_gen3/DATA"
 
@@ -56,6 +63,26 @@ def factory_dependency() -> Factory:
     return Factory(butler=_make_global_butler())
 
 
+def unpack_dataId(butler: Butler, data_id: SerializedDataCoordinate | None) -> DataCoordinate | None:
+    """Convert the serialized dataId back to full DataCoordinate.
+
+    Parameters
+    ----------
+    butler : `lsst.daf.butler.Butler`
+        The butler to use for registry and universe.
+    data_id : `SerializedDataCoordinate` or `None`
+        The serialized form.
+
+    Returns
+    -------
+    dataId : `DataCoordinate` or `None`
+        The DataId usable by registry.
+    """
+    if data_id is None:
+        return None
+    return DataCoordinate.from_simple(data_id, registry=butler.registry)
+
+
 @app.get("/butler/v1/universe", response_model=dict[str, Any])
 def get_dimension_universe(factory: Factory = Depends(factory_dependency)) -> dict[str, Any]:
     """Allow remote client to get dimensions definition."""
@@ -78,3 +105,27 @@ def get_dataset_type(
     butler = factory.create_butler()
     datasetType = butler.get_dataset_type(dataset_type_name)
     return datasetType.to_simple()
+
+
+# Not yet supported: TimeSpan is not yet a pydantic model.
+# collections parameter assumes client-side has resolved regexes.
+@app.post(
+    "/butler/v1/find_dataset/{dataset_type}",
+    summary="Retrieve this dataset definition from collection, dataset type, and dataId",
+    response_model=SerializedDatasetRef,
+    response_model_exclude_unset=True,
+    response_model_exclude_defaults=True,
+    response_model_exclude_none=True,
+)
+def find_dataset(
+    dataset_type: str,
+    query: FindDatasetModel,
+    factory: Factory = Depends(factory_dependency),
+) -> SerializedDatasetRef | None:
+    collection_query = query.collections if query.collections else None
+
+    butler = factory.create_butler()
+    ref = butler.find_dataset(
+        dataset_type, dataId=unpack_dataId(butler, query.dataId), collections=collection_query
+    )
+    return ref.to_simple() if ref else None

python/lsst/daf/butler/remote_butler/server/_server_models.py

@@ -26,3 +26,14 @@
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 """Models used for client/server communication."""
+
+__all__ = ["FindDatasetModel"]
+
+from lsst.daf.butler import SerializedDataCoordinate
+
+from ..._compat import _BaseModelCompat
+
+
+class FindDatasetModel(_BaseModelCompat):
+    dataId: SerializedDataCoordinate
+    collections: list[str]

tests/test_server.py

@@ -27,6 +27,7 @@
 
 import os.path
 import unittest
+import uuid
 
 try:
     # Failing to import any of these should disable the tests.
@@ -37,7 +38,8 @@
     TestClient = None
     app = None
 
-from lsst.daf.butler import Butler
+from lsst.daf.butler import Butler, DatasetRef
+from lsst.daf.butler.tests import DatastoreMock
 from lsst.daf.butler.tests.utils import MetricTestRepo, makeTestTempDir, removeTestTempDir
 
 TESTDIR = os.path.abspath(os.path.dirname(__file__))
@@ -68,6 +70,9 @@ def setUpClass(cls):
         # Override the server's Butler initialization to point at our test repo
         server_butler = Butler.from_config(cls.root, writeable=True)
 
+        # Not yet testing butler.get()
+        DatastoreMock.apply(server_butler)
+
         def create_factory_dependency():
             return Factory(butler=server_butler)
 
@@ -79,6 +84,7 @@ def create_factory_dependency():
 
         # Populate the test server.
         server_butler.import_(filename=os.path.join(TESTDIR, "data", "registry", "base.yaml"))
+        server_butler.import_(filename=os.path.join(TESTDIR, "data", "registry", "datasets-uuid.yaml"))
 
     @classmethod
     def tearDownClass(cls):
@@ -98,6 +104,11 @@ def test_get_dataset_type(self):
         bias_type = self.butler.get_dataset_type("bias")
         self.assertEqual(bias_type.name, "bias")
 
+    def test_find_dataset(self):
+        ref = self.butler.find_dataset("bias", collections="imported_g", detector=1, instrument="Cam1")
+        self.assertIsInstance(ref, DatasetRef)
+        self.assertEqual(ref.id, uuid.UUID("e15ab039-bc8b-4135-87c5-90902a7c0b22"))
+
 
 if __name__ == "__main__":
     unittest.main()