Separate defaults for filters, serializers and compressors in v3

docs/user-guide/config.rst

@@ -28,7 +28,7 @@ Configuration options include the following:
 
 - Default Zarr format ``default_zarr_version``
 - Default array order in memory ``array.order``
-- Default codecs ``array.v3_default_codecs`` and ``array.v2_default_compressor``
+- Default filters, serializers and compressors, e.g. ``array.v3_default_filters``, ``array.v3_default_serializer``, ``array.v3_default_compressors``, ``array.v2_default_filters`` and ``array.v2_default_compressor``
 - Whether empty chunks are written to storage ``array.write_empty_chunks``
 - Async and threading options, e.g. ``async.concurrency`` and ``threading.max_workers``
 - Selections of implementations of codecs, codec pipelines and buffers
@@ -54,19 +54,20 @@ This is the current default configuration::
               'v2_default_filters': {'bytes': [{'id': 'vlen-bytes'}],
                                      'numeric': None,
                                      'string': [{'id': 'vlen-utf8'}]},
-              'v3_default_codecs': {'bytes': [{'name': 'vlen-bytes'},
-                                              {'configuration': {'checksum': False,
-                                                                 'level': 0},
-                                               'name': 'zstd'}],
-                                    'numeric': [{'configuration': {'endian': 'little'},
-                                                 'name': 'bytes'},
-                                                {'configuration': {'checksum': False,
-                                                                   'level': 0},
-                                                 'name': 'zstd'}],
-                                    'string': [{'name': 'vlen-utf8'},
-                                               {'configuration': {'checksum': False,
-                                                                  'level': 0},
-                                                'name': 'zstd'}]},
+              'v3_default_compressors': {'bytes': [{'configuration': {'checksum': False,
+                                                                      'level': 0},
+                                                    'name': 'zstd'}],
+                                         'numeric': [{'configuration': {'checksum': False,
+                                                                        'level': 0},
+                                                      'name': 'zstd'}],
+                                         'string': [{'configuration': {'checksum': False,
+                                                                       'level': 0},
+                                                     'name': 'zstd'}]},
+              'v3_default_filters': {'bytes': [], 'numeric': [], 'string': []},
+              'v3_default_serializer': {'bytes': {'name': 'vlen-bytes'},
+                                        'numeric': {'configuration': {'endian': 'little'},
+                                                    'name': 'bytes'},
+                                        'string': {'name': 'vlen-utf8'}},
               'write_empty_chunks': False},
     'async': {'concurrency': 10, 'timeout': None},
     'buffer': 'zarr.core.buffer.cpu.Buffer',

src/zarr/api/asynchronous.py

@@ -892,7 +892,8 @@ async def create(
         - For Unicode strings, the default is ``VLenUTF8Codec`` and ``ZstdCodec``.
         - For bytes or objects, the default is ``VLenBytesCodec`` and ``ZstdCodec``.
 
-        These defaults can be changed by modifying the value of ``array.v3_default_codecs`` in :mod:`zarr.core.config`.
+        These defaults can be changed by modifying the value of ``array.v3_default_filters``,
+        ``array.v3_default_serializer`` and ``array.v3_default_compressors`` in :mod:`zarr.core.config`.
     compressor : Codec, optional
         Primary compressor to compress chunk data.
         Zarr format 2 only. Zarr format 3 arrays should use ``codecs`` instead.

src/zarr/api/synchronous.py

@@ -788,9 +788,8 @@ def create_array(
         For Zarr format 3, a "filter" is a codec that takes an array and returns an array,
         and these values must be instances of ``ArrayArrayCodec``, or dict representations
         of ``ArrayArrayCodec``.
-        If ``filters`` and ``compressors`` are not specified, then the default codecs for
-        Zarr format 3 will be used.
-        These defaults can be changed by modifying the value of ``array.v3_default_codecs``
+        If no ``filters`` are provided, a default set of filters will be used.
+        These defaults can be changed by modifying the value of ``array.v3_default_filters``
         in :mod:`zarr.core.config`.
         Use ``None`` to omit default filters.
 
@@ -806,22 +805,22 @@ def create_array(
 
         For Zarr format 3, a "compressor" is a codec that takes a bytestream, and
         returns another bytestream. Multiple compressors my be provided for Zarr format 3.
-        If ``filters`` and ``compressors`` are not specified, then the default codecs for
-        Zarr format 3 will be used.
-        These defaults can be changed by modifying the value of ``array.v3_default_codecs``
+        If no ``compressors`` are provided, a default set of compressors will be used.
+        These defaults can be changed by modifying the value of ``array.v3_default_compressors``
         in :mod:`zarr.core.config`.
         Use ``None`` to omit default compressors.
 
         For Zarr format 2, a "compressor" can be any numcodecs codec. Only a single compressor may
         be provided for Zarr format 2.
-        If no ``compressors`` are provided, a default compressor will be used.
-        These defaults can be changed by modifying the value of ``array.v2_default_compressor``
+        If no ``compressor`` is provided, a default compressor will be used.
         in :mod:`zarr.core.config`.
         Use ``None`` to omit the default compressor.
     serializer : dict[str, JSON] | ArrayBytesCodec, optional
         Array-to-bytes codec to use for encoding the array data.
         Zarr format 3 only. Zarr format 2 arrays use implicit array-to-bytes conversion.
-        If no ``serializer`` is provided, the `zarr.codecs.BytesCodec` codec will be used.
+        If no ``serializer`` is provided, a default serializer will be used.
+        These defaults can be changed by modifying the value of ``array.v3_default_serializer``
+        in :mod:`zarr.core.config`.
     fill_value : Any, optional
         Fill value for the array.
     order : {"C", "F"}, optional

src/zarr/core/array.py

@@ -110,7 +110,6 @@
     _parse_array_array_codec,
     _parse_array_bytes_codec,
     _parse_bytes_bytes_codec,
-    _resolve_codec,
     get_pipeline_class,
 )
 from zarr.storage import StoreLike, make_store_path
@@ -469,7 +468,8 @@ async def create(
             - For Unicode strings, the default is ``VLenUTF8Codec`` and ``ZstdCodec``.
             - For bytes or objects, the default is ``VLenBytesCodec`` and ``ZstdCodec``.
 
-            These defaults can be changed by modifying the value of ``array.v3_default_codecs`` in :mod:`zarr.core.config`.
+            These defaults can be changed by modifying the value of ``array.v3_default_filters``,
+            ``array.v3_default_serializer`` and ``array.v3_default_compressors`` in :mod:`zarr.core.config`.
         dimension_names : Iterable[str], optional
             The names of the dimensions (default is None).
             Zarr format 3 only. Zarr format 2 arrays should not use this parameter.
@@ -1715,7 +1715,8 @@ def create(
             - For Unicode strings, the default is ``VLenUTF8Codec`` and ``ZstdCodec``.
             - For bytes or objects, the default is ``VLenBytesCodec`` and ``ZstdCodec``.
 
-            These defaults can be changed by modifying the value of ``array.v3_default_codecs`` in :mod:`zarr.core.config`.
+            These defaults can be changed by modifying the value of ``array.v3_default_filters``,
+            ``array.v3_default_serializer`` and ``array.v3_default_compressors`` in :mod:`zarr.core.config`.
         dimension_names : Iterable[str], optional
             The names of the dimensions (default is None).
             Zarr format 3 only. Zarr format 2 arrays should not use this parameter.
@@ -3698,17 +3699,9 @@ def _build_parents(
 
 def _get_default_codecs(
     np_dtype: np.dtype[Any],
-) -> list[dict[str, JSON]]:
-    default_codecs = zarr_config.get("array.v3_default_codecs")
-    dtype = DataType.from_numpy(np_dtype)
-    if dtype == DataType.string:
-        dtype_key = "string"
-    elif dtype == DataType.bytes:
-        dtype_key = "bytes"
-    else:
-        dtype_key = "numeric"
-
-    return cast(list[dict[str, JSON]], default_codecs[dtype_key])
+) -> tuple[Codec, ...]:
+    filters, serializer, compressors = _get_default_chunk_encoding_v3(np_dtype)
+    return filters + (serializer,) + compressors
 
 
 FiltersLike: TypeAlias = (
@@ -3785,9 +3778,8 @@ async def create_array(
         For Zarr format 3, a "filter" is a codec that takes an array and returns an array,
         and these values must be instances of ``ArrayArrayCodec``, or dict representations
         of ``ArrayArrayCodec``.
-        If ``filters`` and ``compressors`` are not specified, then the default codecs for
-        Zarr format 3 will be used.
-        These defaults can be changed by modifying the value of ``array.v3_default_codecs``
+        If no ``filters`` are provided, a default set of filters will be used.
+        These defaults can be changed by modifying the value of ``array.v3_default_filters``
         in :mod:`zarr.core.config`.
         Use ``None`` to omit default filters.
 
@@ -3803,22 +3795,22 @@ async def create_array(
 
         For Zarr format 3, a "compressor" is a codec that takes a bytestream, and
         returns another bytestream. Multiple compressors my be provided for Zarr format 3.
-        If ``filters`` and ``compressors`` are not specified, then the default codecs for
-        Zarr format 3 will be used.
-        These defaults can be changed by modifying the value of ``array.v3_default_codecs``
+        If no ``compressors`` are provided, a default set of compressors will be used.
+        These defaults can be changed by modifying the value of ``array.v3_default_compressors``
         in :mod:`zarr.core.config`.
         Use ``None`` to omit default compressors.
 
         For Zarr format 2, a "compressor" can be any numcodecs codec. Only a single compressor may
         be provided for Zarr format 2.
-        If no ``compressors`` are provided, a default compressor will be used.
-        These defaults can be changed by modifying the value of ``array.v2_default_compressor``
+        If no ``compressor`` is provided, a default compressor will be used.
         in :mod:`zarr.core.config`.
         Use ``None`` to omit the default compressor.
     serializer : dict[str, JSON] | ArrayBytesCodec, optional
         Array-to-bytes codec to use for encoding the array data.
         Zarr format 3 only. Zarr format 2 arrays use implicit array-to-bytes conversion.
-        If no ``serializer`` is provided, the `zarr.codecs.BytesCodec` codec will be used.
+        If no ``serializer`` is provided, a default serializer will be used.
+        These defaults can be changed by modifying the value of ``array.v3_default_serializer``
+        in :mod:`zarr.core.config`.
     fill_value : Any, optional
         Fill value for the array.
     order : {"C", "F"}, optional
@@ -3997,7 +3989,6 @@ def _get_default_chunk_encoding_v3(
     """
     Get the default ArrayArrayCodecs, ArrayBytesCodec, and BytesBytesCodec for a given dtype.
     """
-    default_codecs = zarr_config.get("array.v3_default_codecs")
     dtype = DataType.from_numpy(np_dtype)
     if dtype == DataType.string:
         dtype_key = "string"
@@ -4006,31 +3997,15 @@ def _get_default_chunk_encoding_v3(
     else:
         dtype_key = "numeric"
 
-    codec_dicts = default_codecs[dtype_key]
-    codecs = tuple(_resolve_codec(c) for c in codec_dicts)
-    array_bytes_maybe = None
-    array_array: list[ArrayArrayCodec] = []
-    bytes_bytes: list[BytesBytesCodec] = []
-
-    for codec in codecs:
-        if isinstance(codec, ArrayBytesCodec):
-            if array_bytes_maybe is not None:
-                raise ValueError(
-                    f"Got two instances of ArrayBytesCodec: {array_bytes_maybe} and {codec}. "
-                    "Only one array-to-bytes codec is allowed."
-                )
-            array_bytes_maybe = codec
-        elif isinstance(codec, ArrayArrayCodec):
-            array_array.append(codec)
-        elif isinstance(codec, BytesBytesCodec):
-            bytes_bytes.append(codec)
-        else:
-            raise TypeError(f"Unexpected codec type: {type(codec)}")
+    default_filters = zarr_config.get("array.v3_default_filters").get(dtype_key)
+    default_serializer = zarr_config.get("array.v3_default_serializer").get(dtype_key)
+    default_compressors = zarr_config.get("array.v3_default_compressors").get(dtype_key)
 
-    if array_bytes_maybe is None:
-        raise ValueError("Required ArrayBytesCodec was not found.")
+    filters = tuple(_parse_array_array_codec(codec_dict) for codec_dict in default_filters)
+    serializer = _parse_array_bytes_codec(default_serializer)
+    compressors = tuple(_parse_bytes_bytes_codec(codec_dict) for codec_dict in default_compressors)
 
-    return tuple(array_array), array_bytes_maybe, tuple(bytes_bytes)
+    return filters, serializer, compressors
 
 
 def _get_default_chunk_encoding_v2(
@@ -4111,34 +4086,15 @@ def _parse_chunk_encoding_v3(
     default_array_array, default_array_bytes, default_bytes_bytes = _get_default_chunk_encoding_v3(
         dtype
     )
-    maybe_bytes_bytes: Iterable[Codec | dict[str, JSON]]
-    maybe_array_array: Iterable[Codec | dict[str, JSON]]
-    out_bytes_bytes: tuple[BytesBytesCodec, ...]
-    if compressors is None:
-        out_bytes_bytes = ()
-
-    elif compressors == "auto":
-        out_bytes_bytes = default_bytes_bytes
 
-    else:
-        if isinstance(compressors, dict | Codec):
-            maybe_bytes_bytes = (compressors,)
-        elif compressors is None:
-            maybe_bytes_bytes = ()
-        else:
-            maybe_bytes_bytes = cast(Iterable[Codec | dict[str, JSON]], compressors)
-
-        out_bytes_bytes = tuple(_parse_bytes_bytes_codec(c) for c in maybe_bytes_bytes)
-    out_array_array: tuple[ArrayArrayCodec, ...]
     if filters is None:
-        out_array_array = ()
+        out_array_array: tuple[ArrayArrayCodec, ...] = ()
     elif filters == "auto":
         out_array_array = default_array_array
     else:
+        maybe_array_array: Iterable[Codec | dict[str, JSON]]
         if isinstance(filters, dict | Codec):
             maybe_array_array = (filters,)
-        elif filters is None:
-            maybe_array_array = ()
         else:
             maybe_array_array = cast(Iterable[Codec | dict[str, JSON]], filters)
         out_array_array = tuple(_parse_array_array_codec(c) for c in maybe_array_array)
@@ -4148,6 +4104,19 @@ def _parse_chunk_encoding_v3(
     else:
         out_array_bytes = _parse_array_bytes_codec(serializer)
 
+    if compressors is None:
+        out_bytes_bytes: tuple[BytesBytesCodec, ...] = ()
+    elif compressors == "auto":
+        out_bytes_bytes = default_bytes_bytes
+    else:
+        maybe_bytes_bytes: Iterable[Codec | dict[str, JSON]]
+        if isinstance(compressors, dict | Codec):
+            maybe_bytes_bytes = (compressors,)
+        else:
+            maybe_bytes_bytes = cast(Iterable[Codec | dict[str, JSON]], compressors)
+
+        out_bytes_bytes = tuple(_parse_bytes_bytes_codec(c) for c in maybe_bytes_bytes)
+
     return out_array_array, out_array_bytes, out_bytes_bytes
 
 

src/zarr/core/config.py

@@ -76,17 +76,20 @@ def reset(self) -> None:
                     "string": [{"id": "vlen-utf8"}],
                     "bytes": [{"id": "vlen-bytes"}],
                 },
-                "v3_default_codecs": {
+                "v3_default_filters": {"numeric": [], "string": [], "bytes": []},
+                "v3_default_serializer": {
+                    "numeric": {"name": "bytes", "configuration": {"endian": "little"}},
+                    "string": {"name": "vlen-utf8"},
+                    "bytes": {"name": "vlen-bytes"},
+                },
+                "v3_default_compressors": {
                     "numeric": [
-                        {"name": "bytes", "configuration": {"endian": "little"}},
                         {"name": "zstd", "configuration": {"level": 0, "checksum": False}},
                     ],
                     "string": [
-                        {"name": "vlen-utf8"},
                         {"name": "zstd", "configuration": {"level": 0, "checksum": False}},
                     ],
                     "bytes": [
-                        {"name": "vlen-bytes"},
                         {"name": "zstd", "configuration": {"level": 0, "checksum": False}},
                     ],
                 },