fix: use importlib_metadata for Python < 3.10.2 (#693)

* Use importlib_metadata for Python < 3.10.2

* Update tests

* Apply suggestions

* Trick mypy

* Fix import order to work with mypy

pyproject.toml

@@ -36,7 +36,7 @@ dependencies = [
   "pyproject_hooks",
   # not actually a runtime dependency, only supplied as there is not "recommended dependency" support
   'colorama; os_name == "nt"',
-  'importlib-metadata >= 4.6; python_version < "3.10"',  # Not required for 3.8+, but fixes a stdlib bug
+  'importlib-metadata >= 4.6; python_full_version < "3.10.2"',  # Not required for 3.8+, but fixes a stdlib bug
   'tomli >= 1.1.0; python_version < "3.11"',
 ]
 

src/build/_importlib.py

@@ -3,12 +3,13 @@
 
 if sys.version_info < (3, 8):
     import importlib_metadata as metadata
-elif sys.version_info < (3, 9, 10) or (3, 10, 0) <= sys.version_info < (3, 10, 2):
+elif sys.version_info >= (3, 10, 2):
+    from importlib import metadata
+else:
     try:
         import importlib_metadata as metadata
     except ModuleNotFoundError:
+        # helps bootstrapping when dependencies aren't installed
         from importlib import metadata
-else:
-    from importlib import metadata
 
 __all__ = ['metadata']

tests/test_util.py

@@ -14,6 +14,7 @@ def test_wheel_metadata(package_test_setuptools, isolated):
 
     assert metadata['name'] == 'test-setuptools'
     assert metadata['version'] == '1.0.0'
+    assert isinstance(metadata.json, dict)
 
 
 @pytest.mark.network
@@ -26,6 +27,7 @@ def test_wheel_metadata_isolation(package_test_flit):
 
     assert metadata['name'] == 'test_flit'
     assert metadata['version'] == '1.0.0'
+    assert isinstance(metadata.json, dict)
 
     with pytest.raises(
         build.BuildBackendException,
@@ -42,3 +44,4 @@ def test_with_get_requires(package_test_metadata):
     assert metadata['name'] == 'test-metadata'
     assert str(metadata['version']) == '1.0.0'
     assert metadata['summary'] == 'hello!'
+    assert isinstance(metadata.json, dict)