fix pcodec resolution failure

changes/3483.bugfix.md

@@ -0,0 +1 @@
+Fix a bug that prevented `PCodec` from being properly resolved when loading arrays using that compressor.

pyproject.toml

@@ -84,7 +84,9 @@ test = [
     "pytest-xdist",
     "packaging",
     "tomlkit",
-    "uv"
+    "uv",
+    "pcodec",
+    "zfpy",
 ]
 remote_tests = [
     'zarr[remote]',

src/zarr/codecs/__init__.py

@@ -85,7 +85,7 @@
 register_codec(
     "numcodecs.jenkins_lookup3", JenkinsLookup3, qualname="zarr.codecs.numcodecs.JenkinsLookup3"
 )
-register_codec("numcodecs.pcodec", PCodec, qualname="zarr.codecs.numcodecs.pcodec")
+register_codec("numcodecs.pcodec", PCodec, qualname="zarr.codecs.numcodecs.PCodec")
 register_codec("numcodecs.packbits", PackBits, qualname="zarr.codecs.numcodecs.PackBits")
 register_codec("numcodecs.quantize", Quantize, qualname="zarr.codecs.numcodecs.Quantize")
 register_codec("numcodecs.shuffle", Shuffle, qualname="zarr.codecs.numcodecs.Shuffle")

tests/test_codecs/test_numcodecs.py

@@ -12,7 +12,7 @@
 from zarr.abc.numcodec import _is_numcodec, _is_numcodec_cls
 from zarr.codecs import numcodecs as _numcodecs
 from zarr.errors import ZarrUserWarning
-from zarr.registry import get_numcodec
+from zarr.registry import get_codec_class, get_numcodec
 
 if TYPE_CHECKING:
     from collections.abc import Iterator
@@ -74,18 +74,23 @@ def test_is_numcodec_cls() -> None:
 
 ALL_CODECS = tuple(
     filter(
-        lambda v: isinstance(v, _numcodecs._NumcodecsCodec),
+        lambda v: issubclass(v, _numcodecs._NumcodecsCodec) and hasattr(v, "codec_name"),
         tuple(getattr(_numcodecs, cls_name) for cls_name in _numcodecs.__all__),
     )
 )
 
 
+@pytest.mark.parametrize("codec_cls", ALL_CODECS)
+def test_get_codec_class(codec_cls: type[_numcodecs._NumcodecsCodec]) -> None:
+    assert get_codec_class(codec_cls.codec_name) == codec_cls  # type: ignore[comparison-overlap]
+
+
 @pytest.mark.parametrize("codec_class", ALL_CODECS)
 def test_docstring(codec_class: type[_numcodecs._NumcodecsCodec]) -> None:
     """
     Test that the docstring for the zarr.numcodecs codecs references the wrapped numcodecs class.
     """
-    assert "See :class:`numcodecs." in codec_class.__doc__  # type: ignore[operator]
+    assert "See [numcodecs." in codec_class.__doc__  # type: ignore[operator]
 
 
 @pytest.mark.parametrize(