Test zarr compressor and filters are correct in parallel case

sgkit/io/vcfzarr_reader.py

@@ -333,10 +333,20 @@ def concat_zarrs_optimized(
             [group[var] for group in zarr_groups], dtype=dtype
         )
 
-        _to_zarr_kwargs = dict(fill_value=None)
+        _to_zarr_kwargs = dict(
+            compressor=first_zarr_group[var].compressor,
+            filters=first_zarr_group[var].filters,
+            fill_value=None,
+        )
         if not fix_strings and arr.dtype == "O":
             # We assume that all object dtypes are variable length strings
-            _to_zarr_kwargs["object_codec"] = numcodecs.VLenUTF8()
+            var_len_str_codec = numcodecs.VLenUTF8()
+            _to_zarr_kwargs["object_codec"] = var_len_str_codec
+            # Remove from filters to avoid double encoding error
+            if var_len_str_codec in first_zarr_group[var].filters:
+                filters = list(first_zarr_group[var].filters)
+                filters.remove(var_len_str_codec)
+                _to_zarr_kwargs["filters"] = filters
 
         d = _to_zarr(  # type: ignore[no-untyped-call]
             arr,

sgkit/tests/io/vcf/test_vcf_reader.py

@@ -229,6 +229,43 @@ def test_vcf_to_zarr__compressor_and_filters(shared_datadir, is_path, tmp_path):
     assert z["variant_id_mask"].filters is None
 
 
+@pytest.mark.parametrize(
+    "is_path",
+    [True, False],
+)
+@pytest.mark.filterwarnings("ignore::sgkit.io.vcf.MaxAltAllelesExceededWarning")
+def test_vcf_to_zarr__parallel_compressor_and_filters(
+    shared_datadir, is_path, tmp_path
+):
+    path = path_for_test(shared_datadir, "CEUTrio.20.21.gatk3.4.g.vcf.bgz", is_path)
+    output = tmp_path.joinpath("vcf_concat.zarr").as_posix()
+    regions = ["20", "21"]
+
+    default_compressor = Blosc("zlib", 1, Blosc.NOSHUFFLE)
+    variant_id_compressor = Blosc("zlib", 2, Blosc.NOSHUFFLE)
+    encoding = dict(
+        variant_id=dict(compressor=variant_id_compressor),
+        variant_id_mask=dict(filters=None),
+    )
+    vcf_to_zarr(
+        path,
+        output,
+        regions=regions,
+        chunk_length=5_000,
+        compressor=default_compressor,
+        encoding=encoding,
+    )
+
+    # look at actual Zarr store to check compressor and filters
+    z = zarr.open(output)
+    assert z["call_genotype"].compressor == default_compressor
+    assert z["call_genotype"].filters is None
+    assert z["call_genotype_mask"].filters == [PackBits()]
+
+    assert z["variant_id"].compressor == variant_id_compressor
+    assert z["variant_id_mask"].filters is None
+
+
 @pytest.mark.parametrize(
     "is_path",
     [True, False],