Rename Zip index file name

And remove some duplicated code that was writing the index
a second time.

python/lsst/daf/butler/datastore/_datastore.py

@@ -1049,9 +1049,8 @@ def retrieveArtifacts(
             If `True` allow transfers to overwrite existing files at the
             destination.
         write_index : `bool`, optional
-            If `True` write a file at the top level called ``_index.json``
-            containing a serialization of a `ZipIndex` for the downloaded
-            datasets.
+            If `True` write a file at the top level containing a serialization
+            of a `ZipIndex` for the downloaded datasets.
         add_prefix : `bool`, optional
             If `True` and if ``preserve_path`` is `False`, apply a prefix to
             the filenames corresponding to some part of the dataset ref ID.

python/lsst/daf/butler/datastores/chainedDatastore.py

@@ -842,9 +842,8 @@ def retrieveArtifacts(
             If `True` allow transfers to overwrite existing files at the
             destination.
         write_index : `bool`, optional
-            If `True` write a file at the top level called ``_index.json``
-            containing a serialization of a `ZipIndex` for the downloaded
-            datasets.
+            If `True` write a file at the top level containing a serialization
+            of a `ZipIndex` for the downloaded datasets.
         add_prefix : `bool`, optional
             Add a prefix based on the DatasetId. Only used if ``preserve_path``
             is `False`.

python/lsst/daf/butler/datastores/fileDatastore.py

@@ -2073,9 +2073,8 @@ def retrieveArtifacts(
             If `True` allow transfers to overwrite existing files at the
             destination.
         write_index : `bool`, optional
-            If `True` write a file at the top level called ``_index.json``
-            containing a serialization of a `ZipIndex` for the downloaded
-            datasets.
+            If `True` write a file at the top level containing a serialization
+            of a `ZipIndex` for the downloaded datasets.
         add_prefix : `bool`, optional
             If `True` and if ``preserve_path`` is `False`, apply a prefix to
             the filenames corresponding to some part of the dataset ref ID.

python/lsst/daf/butler/datastores/file_datastore/retrieve_artifacts.py

@@ -195,7 +195,7 @@ class ZipIndex(BaseModel):
     info_map: dict[str, SerializedStoredFileInfo]
     """Mapping of each Zip member to the associated datastore record."""
 
-    index_name: ClassVar[str] = "_index.json"
+    index_name: ClassVar[str] = "_butler_zip_index.json"
     """Name to use when saving the index to a file."""
 
     def generate_uuid5(self) -> uuid.UUID:

python/lsst/daf/butler/datastores/inMemoryDatastore.py

@@ -552,9 +552,8 @@ def retrieveArtifacts(
             If `True` allow transfers to overwrite existing files at the
             destination.
         write_index : `bool`, optional
-            If `True` write a file at the top level called ``_index.json``
-            containing a serialization of a `ZipIndex` for the downloaded
-            datasets.
+            If `True` write a file at the top level containing a serialization
+            of a `ZipIndex` for the downloaded datasets.
         add_prefix : `bool`, optional
             If `True` and if ``preserve_path`` is `False`, apply a prefix to
             the filenames corresponding to some part of the dataset ref ID.

python/lsst/daf/butler/direct_butler/_direct_butler.py

@@ -1309,20 +1309,14 @@ def retrieveArtifacts(
     ) -> list[ResourcePath]:
         # Docstring inherited.
         outdir = ResourcePath(destination)
-        paths, id_map, info_map = self._datastore.retrieveArtifacts(
+        paths, _, _ = self._datastore.retrieveArtifacts(
             refs,
             outdir,
             transfer=transfer,
             preserve_path=preserve_path,
             overwrite=overwrite,
+            write_index=True,
         )
-        # Write the index file.
-        index = ZipIndex.from_artifact_maps(
-            refs, id_map, info_map, ResourcePath(destination, forceDirectory=True)
-        )
-        index_path = outdir.join("_index.json")
-        with index_path.open("w") as fd:
-            print(index.model_dump_json(exclude_defaults=True, exclude_unset=True), file=fd)
         return paths
 
     def exists(

tests/test_butler.py

@@ -88,6 +88,7 @@ def mock_aws(*args: Any, **kwargs: Any) -> Any:  # type: ignore[no-untyped-def]
 )
 from lsst.daf.butler.datastore import NullDatastore
 from lsst.daf.butler.datastore.file_templates import FileTemplate, FileTemplateValidationError
+from lsst.daf.butler.datastores.file_datastore.retrieve_artifacts import ZipIndex
 from lsst.daf.butler.datastores.fileDatastore import FileDatastore
 from lsst.daf.butler.direct_butler import DirectButler
 from lsst.daf.butler.registry import (
@@ -362,7 +363,7 @@ def runPutGetTest(self, storageClass: StorageClass, datasetTypeName: str) -> But
                             self.assertGreater(len(transferred), 0)
                             artifacts = list(ResourcePath.findFileResources([destination]))
                             # Filter out the index file.
-                            artifacts = [a for a in artifacts if a.basename() != "_index.json"]
+                            artifacts = [a for a in artifacts if a.basename() != ZipIndex.index_name]
                             self.assertEqual(set(transferred), set(artifacts))
 
                             for artifact in transferred: