Fix importlib for py39 and older

.github/workflows/tox-tests.yml

@@ -67,3 +67,20 @@ jobs:
         run: pip install tox
       - name: Run Tox
         run: tox -e py3-bandit
+  test-py39:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - name: Setup Python
+        uses: actions/setup-python@v2
+        with:
+          python-version: "3.9"
+      - name: Install OS packages
+        run: |
+          sudo apt-get -y update
+          sudo apt-get install -y libkrb5-dev
+      - name: Install Tox
+        run: pip install tox
+      - name: Run Tox
+        run: tox -e py39
+

requirements.txt

@@ -1,2 +1,2 @@
 pluggy
-setuptools
+importlib-metadata; python_version < "3.10"

src/pubtools/_impl/pluggy.py

@@ -1,8 +1,12 @@
 import logging
 import sys
 from contextlib import contextmanager
-from importlib.metadata import entry_points
 
+if sys.version_info >= (3, 10):
+    from importlib.metadata import entry_points
+else:  # pragma: no cover
+    # for older python use non-standard compatible module
+    from importlib_metadata import entry_points
 import pluggy
 
 LOG = logging.getLogger("pubtools")

tests/hooks/test_entry_points.py

@@ -1,42 +1,49 @@
 import sys
-from importlib import metadata
-from importlib.metadata import EntryPoint
 
+if sys.version_info >= (3, 10):
+    from importlib.metadata import EntryPoint
+else:
+    from importlib_metadata import EntryPoint
+
+from pubtools._impl import pluggy
 from pubtools.pluggy import task_context
 
 
 def test_task_context_loads_entry_points(monkeypatch):
     """task_context eagerly resolves console_scripts and pubtools.hooks entry points."""
 
-    target_mod = "pydoc"
-
-    # Define the mock entry points EntryPoint(name, value, group)
-    ep1 = EntryPoint(
-        name="some-script", value="pubtools.pluggy", group="console_scripts"
-    )
-    ep2 = EntryPoint(name="anything", value=target_mod, group="pubtools.hooks")
-
-    mock_entry_points = [ep1, ep2]
-
-    # Monkeypatch metadata.entry_points globally
-    # In the new API, mock the function that task_context() will call
-    def mock_eps(**kwargs):
-        group = kwargs.get("group")
-        if group:
-            return [ep for ep in mock_entry_points if ep.group == group]
-        return metadata.EntryPoints(mock_entry_points)
-
-    monkeypatch.setattr(metadata, "entry_points", mock_eps)
-
-    # "un-import" these modules (Ensure they are in sys.modules first so del doesn't fail,
-    # though usually they are already there from imports above)
-    for mod in ["pubtools.pluggy", target_mod]:
-        if mod in sys.modules:
-            del sys.modules[mod]
+    # importlib.metadata.entry_points() reads from installed package metadata;
+    # there is no mutable entry map to patch. Patch entry_points in the pluggy
+    # module so it returns our custom entry points by group.
+    console_scripts = [
+        # This one is pubtools.*, so it should be loaded by resolve_hooks.
+        EntryPoint("some-script", "pubtools.pluggy", "console_scripts"),
+        # This should be ignored (module does not start with "pubtools").
+        EntryPoint("other-script", "something.non.existent", "console_scripts"),
+    ]
+    pubtools_hooks = [
+        EntryPoint("anything", "pytest", "pubtools.hooks"),
+    ]
+
+    def fake_entry_points(group=None):
+        if group == "console_scripts":
+            return console_scripts
+        if group == "pubtools.hooks":
+            return pubtools_hooks
+        return []
+
+    monkeypatch.setattr(pluggy, "entry_points", fake_entry_points)
+
+    # Effectively "un-import" these modules so we can observe that task_context
+    # has the side-effect of importing them.
+    assert "pubtools.pluggy" in sys.modules
+    assert "pytest" in sys.modules
+    del sys.modules["pubtools.pluggy"]
+    del sys.modules["pytest"]
 
     with task_context():
         # As soon as we've entered the task context, the modules referenced from
         # those entry points should be imported, ensuring we can now use hooks with
         # everything registered
         assert "pubtools.pluggy" in sys.modules
-        assert target_mod in sys.modules
+        assert "pytest" in sys.modules

tox.ini

@@ -6,6 +6,9 @@ deps=-rtest-requirements.txt
 commands=pytest -v {posargs}
 whitelist_externals=sh
 
+[testenv:py39]
+deps=-rtest-requirements.in
+
 [testenv:cov]
 usedevelop=true
 commands=