fix #251

dascore/clients/dirspool.py

@@ -49,8 +49,9 @@ def __init__(
         index_path: Path | None = None,
         preferred_format: str | None = None,
         select_kwargs: dict | None = None,
+        merge_kwargs: dict | None = None,
     ):
-        super().__init__(select_kwargs=select_kwargs)
+        super().__init__(select_kwargs=select_kwargs, merge_kwargs=merge_kwargs)
         # Init file spool from another file spool
         if isinstance(base_path, self.__class__):
             self.__dict__.update(copy.deepcopy(base_path.__dict__))
@@ -60,6 +61,7 @@ def __init__(
             self.indexer = base_path
         elif isinstance(base_path, Path | str):
             self.indexer = DirectoryIndexer(base_path, index_path=index_path)
+        assert hasattr(self, "indexer"), "indexer not set."
         self._preferred_format = preferred_format
 
     def __rich__(self):

dascore/core/spool.py

@@ -328,14 +328,11 @@ def __init__(
         self._select_kwargs = {} if select_kwargs is None else select_kwargs
         self._merge_kwargs = {} if merge_kwargs is None else merge_kwargs
 
-    def __getitem__(self, item):
-        out = self._get_patches_from_index(item)
-        # a single index was used, should return a single patch
-        if not isinstance(item, slice):
-            out = self._unbox_patch(out)
-        # a slice was used, return a sub-spool
-        else:
-            out = self.__class__(out)
+    def __getitem__(self, item) -> PatchType | BaseSpool:
+        if isinstance(item, slice):  # a slice was used, return a sub-spool
+            out = self.new_from_df(df=self._df.iloc[item])
+        else:  # a single index was used, should return a single patch
+            out = self._unbox_patch(self._get_patches_from_index(item))
         return out
 
     def __len__(self):
@@ -354,17 +351,14 @@ def _get_patches_from_index(self, df_ind):
         """Given an index (from current df), return the corresponding patch."""
         source = self._source_df
         instruction = self._instruction_df
-        if isinstance(df_ind, slice):  # handle slicing
-            df1 = instruction.loc[instruction["current_index"].values[df_ind]]
-        else:  # Filter instruction df to only include current index.
-            # handle negative index.
-            df_ind = df_ind if df_ind >= 0 else len(self._df) + df_ind
-            try:
-                inds = self._df.index[df_ind]
-            except IndexError:
-                msg = f"index of [{df_ind}] is out of bounds for spool."
-                raise IndexError(msg)
-            df1 = instruction[instruction["current_index"] == inds]
+        # handle negative index.
+        df_ind = df_ind if df_ind >= 0 else len(self._df) + df_ind
+        try:
+            inds = self._df.index[df_ind]
+        except IndexError:
+            msg = f"index of [{df_ind}] is out of bounds for spool."
+            raise IndexError(msg)
+        df1 = instruction[instruction["current_index"] == inds]
         assert not df1.empty
         joined = df1.join(source.drop(columns=df1.columns, errors="ignore"))
         return self._patch_from_instruction_df(joined)

tests/test_clients/test_dirspool.py

@@ -359,6 +359,28 @@ def test_str_columns_in_dataframe(self, diverse_directory_spool):
         assert set(df.columns).issuperset(set(expected))
 
 
+class TestIndexing:
+    """Tests for indexing directory spool."""
+
+    def test_slice_to_start(self, diverse_directory_spool):
+        """Ensure a slice returns a subspool (shouldn't load data)."""
+        out = diverse_directory_spool[0:2]
+        assert isinstance(out, out.__class__)
+
+    def test_slice_to_end(self, diverse_directory_spool):
+        """Ensure a slice from the end returns a subspool."""
+        out = diverse_directory_spool[-2:]
+        assert isinstance(out, out.__class__)
+
+    def test_sliced_spool_has_indexer(self, diverse_directory_spool):
+        """Ensure the sliced spool still has its indexer."""
+        out = diverse_directory_spool[1:3]
+        assert hasattr(out, "indexer")
+        assert out.indexer.path == diverse_directory_spool.indexer.path
+        # ensure we can still load patches from sliced dirspool
+        assert isinstance(out[0], dc.Patch)
+
+
 class TestFileSpoolIntegrations:
     """Small integration tests for the file spool."""