New configuration setting slice_source_kwargs

CHANGES.md

@@ -9,6 +9,11 @@
   - Introduced `SliceSource.close()` so
     [contextlib.closing()](https://docs.python.org/3/library/contextlib.html#contextlib.closing)
     is applicable. Deprecated `SliceSource.dispose()`.
+
+  - Introduced new optional configuration setting `slice_source_kwargs` that
+    contains keyword-arguments, which are passed to a configured `slice_source` together with 
+    each slice item.
+
 
 ## Version 0.6.0 (from 2024-03-12)
 

docs/guide.md

@@ -760,6 +760,10 @@ argument to your slice source.
     - `dict`: keyword arguments only;
     - Any other type is interpreted as single positional argument.
 
+You can also pass extra keyword arguments to your slice source using the 
+`slice_source_kwargs` setting. Keyword arguments passed as slice items take 
+precedence, that is, they overwrite arguments passed by `slice_source_kawrgs`.
+
 In addition, your slice source function or class constructor specified by 
 `slice_source` may define a 1st positional argument or keyword argument 
 named `ctx`, which will receive the current processing context of type 

tests/config/test_config.py

@@ -162,6 +162,24 @@ def test_slice_source_as_type(self):
                 }
             )
 
+    def test_slice_source_kwargs(self):
+        config = Config(
+            {
+                "target_dir": "memory://target.zarr",
+            }
+        )
+        self.assertEqual(None, config.slice_source_kwargs)
+
+        config = Config(
+            {
+                "target_dir": "memory://target.zarr",
+                "slice_source_kwargs": {"a": 1, "b": True, "c": "nearest"},
+            }
+        )
+        self.assertEqual(
+            {"a": 1, "b": True, "c": "nearest"}, config.slice_source_kwargs
+        )
+
 
 def new_custom_slice_source(ctx: Context, index: int):
     return CustomSliceSource(ctx, index)

tests/config/test_schema.py

@@ -31,6 +31,7 @@ def test_get_config_schema(self):
                 "slice_engine",
                 "slice_polling",
                 "slice_source",
+                "slice_source_kwargs",
                 "slice_storage_options",
                 "target_storage_options",
                 "target_dir",

tests/slice/test_cm.py

@@ -25,7 +25,7 @@
 # noinspection PyUnusedLocal
 
 
-# noinspection PyShadowingBuiltins,PyRedeclaration
+# noinspection PyShadowingBuiltins,PyRedeclaration,PyMethodMayBeStatic
 class OpenSliceDatasetTest(unittest.TestCase):
     def setUp(self):
         clear_memory_fs()
@@ -164,7 +164,7 @@ def get_dataset(name):
         with slice_cm as slice_ds:
             self.assertIsInstance(slice_ds, xr.Dataset)
 
-    def test_slice_item_is_slice_source(self):
+    def test_slice_item_is_slice_source_arg(self):
         class MySliceSource(SliceSource):
             def __init__(self, name):
                 self.uri = f"memory://{name}.zarr"
@@ -191,7 +191,7 @@ def close(self):
         with slice_cm as slice_ds:
             self.assertIsInstance(slice_ds, xr.Dataset)
 
-    def test_slice_item_is_deprecated_slice_source(self):
+    def test_slice_item_is_deprecated_slice_source_arg(self):
         class MySliceSource(SliceSource):
             def __init__(self, name):
                 self.uri = f"memory://{name}.zarr"
@@ -219,6 +219,33 @@ def dispose(self):
             with slice_cm as slice_ds:
                 self.assertIsInstance(slice_ds, xr.Dataset)
 
+    def test_slice_item_is_slice_source_arg_with_extra_kwargs(self):
+        class MySliceSource(SliceSource):
+            def __init__(self, *args, **kwargs):
+                self.args = args
+                self.kwargs = kwargs
+
+            def get_dataset(self):
+                return xr.Dataset()
+
+        ctx = Context(
+            dict(
+                target_dir="memory://target.zarr",
+                slice_source=MySliceSource,
+                slice_source_kwargs={"a": 1, "b": True, "c": "nearest"},
+            )
+        )
+        slice_cm = open_slice_dataset(ctx, (["bibo"], {"a": 2, "d": 3.14}))
+        self.assertIsInstance(slice_cm, SliceSourceContextManager)
+        slice_source = slice_cm.slice_source
+        self.assertIsInstance(slice_source, MySliceSource)
+        with slice_cm as slice_ds:
+            self.assertIsInstance(slice_ds, xr.Dataset)
+            self.assertEqual(slice_source.args, ("bibo",))
+            self.assertEqual(
+                slice_source.kwargs, {"a": 2, "b": True, "c": "nearest", "d": 3.14}
+            )
+
 
 class IsContextManagerTest(unittest.TestCase):
     """Assert that context managers are identified by isinstance()"""

zappend/config/config.py

@@ -133,6 +133,13 @@ def slice_source(self) -> Callable[[...], Any] | None:
         """
         return self._slice_source
 
+    @property
+    def slice_source_kwargs(self) -> dict[str, Any] | None:
+        """Extra keyword-arguments passed to a specified `slice_source`
+        together with each slice item.
+        """
+        return self._config.get("slice_source_kwargs")
+
     @property
     def slice_storage_options(self) -> dict[str, Any] | None:
         """The configured slice storage options to be used

zappend/config/schema.py

@@ -643,6 +643,14 @@
             "type": "string",
             "minLength": 1,
         },
+        slice_source_kwargs={
+            "description": (
+                "Extra keyword-arguments passed to a configured `slice_source`"
+                " together with each slice item."
+            ),
+            "type": "object",
+            "additionalProperties": True,
+        },
         slice_engine={
             "description": (
                 "The name of the engine to be used for opening"

zappend/slice/callable.py

@@ -30,6 +30,10 @@ def invoke_slice_callable(
         A slice item of type `SliceItem`.
     """
     slice_args, slice_kwargs = to_slice_args(slice_item)
+    if ctx.config.slice_source_kwargs:
+        extra_kwargs = dict(ctx.config.slice_source_kwargs)
+        extra_kwargs.update(slice_kwargs)
+        slice_kwargs = extra_kwargs
 
     signature = inspect.signature(slice_callable)
     ctx_parameter = signature.parameters.get("ctx")