Fix default entrypoint handling on older Pythons

.github/workflows/ci-linux.yaml

@@ -50,7 +50,7 @@ jobs:
         run: |
           conda activate env
           export DISABLE_NUMCODECS_AVX2=""
-          python -m pip install -v -e .[test,msgpack,zfpy]
+          python -m pip install -v -e .[test,test_extras,msgpack,zfpy]
 
       - name: List installed packages
         shell: "bash -l {0}"

.github/workflows/ci-osx.yaml

@@ -50,7 +50,7 @@ jobs:
         run: |
           conda activate env
           export DISABLE_NUMCODECS_AVX2=""
-          python -m pip install -v -e .[test,msgpack,zfpy]
+          python -m pip install -v -e .[test,test_extras,msgpack,zfpy]
 
       - name: List installed packages
         shell: "bash -l {0}"

.github/workflows/ci-windows.yaml

@@ -42,7 +42,7 @@ jobs:
         shell: "bash -l {0}"
         run: |
           conda activate env
-          python -m pip install -v -e .[test,msgpack,zfpy]
+          python -m pip install -v -e .[test,test_extras,msgpack,zfpy]
 
       - name: List installed packages
         shell: "bash -l {0}"

docs/release.rst

@@ -16,6 +16,8 @@ Fix
 
 * ``Codec`` is now derived from ``abc.ABC``
   By :user:`Mads R. B. Kristensen <madsbk>`, :issue:`472`.
+* Fix handling of entry points on older Python versions where ``importlib_metadata`` compatibility is concerned
+  By :user:`Vyas Ramasubramani <vyasr>`, :issue:`478`.
 * Make shuffle pyx functions ``noexcept``
   By :user:`Martin Durant <martindurant>`, :issue:`477`.
 

numcodecs/registry.py

@@ -16,7 +16,7 @@ def run_entrypoints():
         entries.update({e.name: e for e in eps.select(group="numcodecs.codecs")})
     else:
         # Otherwise, fallback to using get
-        entries.update(eps.get("numcodecs.codecs", []))
+        entries.update({e.name: e for e in eps.get("numcodecs.codecs", [])})
 
 
 run_entrypoints()

numcodecs/tests/test_entrypoints.py

@@ -19,6 +19,7 @@ def set_path():
     numcodecs.registry.codec_registry.pop("test")
 
 
-def test_entrypoint_codec(set_path):
+@pytest.mark.usefixtures("set_path")
+def test_entrypoint_codec():
     cls = numcodecs.registry.get_codec({"id": "test"})
     assert cls.codec_id == "test"

numcodecs/tests/test_entrypoints_backport.py

@@ -0,0 +1,32 @@
+import os.path
+import pkgutil
+import sys
+
+import pytest
+
+from multiprocessing import Process
+
+import numcodecs.registry
+
+if not pkgutil.find_loader("importlib_metadata"):  # pragma: no cover
+    pytest.skip("This test module requires importlib_metadata to be installed")
+
+here = os.path.abspath(os.path.dirname(__file__))
+
+
+def get_entrypoints_with_importlib_metadata_loaded():
+    # importlib_metadata patches importlib.metadata, which can lead to breaking changes
+    # to the APIs of EntryPoint objects used when registering entrypoints. Attempt to
+    # isolate those changes to just this test.
+    import importlib_metadata  # noqa: F401
+    sys.path.append(here)
+    numcodecs.registry.run_entrypoints()
+    cls = numcodecs.registry.get_codec({"id": "test"})
+    assert cls.codec_id == "test"
+
+
+def test_entrypoint_codec_with_importlib_metadata():
+    p = Process(target=get_entrypoints_with_importlib_metadata_loaded)
+    p.start()
+    p.join()
+    assert p.exitcode == 0

pyproject.toml

@@ -56,6 +56,9 @@ test = [
     "pytest",
     "pytest-cov",
 ]
+test_extras = [
+    "importlib_metadata",
+]
 msgpack = [
     "msgpack",
 ]