Fix egg_info.writers entry point module path (#829)

kernels/pyproject.toml

@@ -63,7 +63,7 @@ docs = [
 kernels = "kernels.cli:main"
 
 [project.entry-points."egg_info.writers"]
-"kernels.lock" = "kernels.lockfile:write_egg_lockfile"
+"kernels.lock" = "kernels.locking:write_egg_lockfile"
 
 [tool.maturin]
 module-name = "kernels._rust"

kernels/tests/test_entry_points.py

@@ -0,0 +1,19 @@
+from importlib.metadata import distribution
+
+import pytest
+
+
+def test_egg_info_writer_entry_point_is_importable():
+    """The `egg_info.writers` entry point is loaded by setuptools during *any*
+    `egg_info` run in an environment where `kernels` is installed, including
+    builds of unrelated packages. If it points at a module that is not shipped,
+    every such build fails with `ModuleNotFoundError`."""
+    entry_points = [ep for ep in distribution("kernels").entry_points if ep.group == "egg_info.writers"]
+    assert entry_points, "no egg_info.writers entry point registered"
+
+    for ep in entry_points:
+        try:
+            writer = ep.load()
+        except ModuleNotFoundError as e:
+            pytest.fail(f"entry point {ep.name} = {ep.value!r} is not importable: {e}")
+        assert callable(writer)