Add unit test for issue with attr:

setuptools/tests/config/test_expand.py

@@ -3,7 +3,6 @@
 import pytest
 
 from distutils.errors import DistutilsOptionError
-from setuptools.command.sdist import sdist
 from setuptools.config import expand
 from setuptools.discovery import find_package_path
 
@@ -56,34 +55,66 @@ def test_read_files(tmp_path, monkeypatch):
         expand.read_files(["../a.txt"], tmp_path)
 
 
-def test_read_attr(tmp_path, monkeypatch):
-    files = {
-        "pkg/__init__.py": "",
-        "pkg/sub/__init__.py": "VERSION = '0.1.1'",
-        "pkg/sub/mod.py": (
-            "VALUES = {'a': 0, 'b': {42}, 'c': (0, 1, 1)}\n"
-            "raise SystemExit(1)"
-        ),
-    }
-    write_files(files, tmp_path)
-
-    with monkeypatch.context() as m:
-        m.chdir(tmp_path)
-        # Make sure it can read the attr statically without evaluating the module
-        assert expand.read_attr('pkg.sub.VERSION') == '0.1.1'
-        values = expand.read_attr('lib.mod.VALUES', {'lib': 'pkg/sub'})
-
-    assert values['a'] == 0
-    assert values['b'] == {42}
-
-    # Make sure the same APIs work outside cwd
-    assert expand.read_attr('pkg.sub.VERSION', root_dir=tmp_path) == '0.1.1'
-    values = expand.read_attr('lib.mod.VALUES', {'lib': 'pkg/sub'}, tmp_path)
-    assert values['c'] == (0, 1, 1)
+class TestReadAttr:
+    def test_read_attr(self, tmp_path, monkeypatch):
+        files = {
+            "pkg/__init__.py": "",
+            "pkg/sub/__init__.py": "VERSION = '0.1.1'",
+            "pkg/sub/mod.py": (
+                "VALUES = {'a': 0, 'b': {42}, 'c': (0, 1, 1)}\n"
+                "raise SystemExit(1)"
+            ),
+        }
+        write_files(files, tmp_path)
+
+        with monkeypatch.context() as m:
+            m.chdir(tmp_path)
+            # Make sure it can read the attr statically without evaluating the module
+            assert expand.read_attr('pkg.sub.VERSION') == '0.1.1'
+            values = expand.read_attr('lib.mod.VALUES', {'lib': 'pkg/sub'})
+
+        assert values['a'] == 0
+        assert values['b'] == {42}
+
+        # Make sure the same APIs work outside cwd
+        assert expand.read_attr('pkg.sub.VERSION', root_dir=tmp_path) == '0.1.1'
+        values = expand.read_attr('lib.mod.VALUES', {'lib': 'pkg/sub'}, tmp_path)
+        assert values['c'] == (0, 1, 1)
+
+    def test_import_order(self, tmp_path):
+        """
+        Sometimes the import machinery will import the parent package of a nested
+        module, which triggers side-effects and might create problems (see issue #3176)
+
+        ``read_attr`` should bypass these limitations by resolving modules statically
+        (via ast.literal_eval).
+        """
+        files = {
+            "src/pkg/__init__.py": "from .main import func\nfrom .about import version",
+            "src/pkg/main.py": "import super_complicated_dep\ndef func(): return 42",
+            "src/pkg/about.py": "version = '42'",
+        }
+        write_files(files, tmp_path)
+        attr_desc = "pkg.about.version"
+        package_dir = {"": "src"}
+        # `import super_complicated_dep` should not run, otherwise the build fails
+        assert expand.read_attr(attr_desc, package_dir, tmp_path) == "42"
 
 
-def test_resolve_class():
-    assert expand.resolve_class("setuptools.command.sdist.sdist") == sdist
+@pytest.mark.parametrize(
+    'package_dir, file, module, return_value',
+    [
+        ({"": "src"}, "src/pkg/main.py", "pkg.main", 42),
+        ({"pkg": "lib"}, "lib/main.py", "pkg.main", 13),
+        ({}, "single_module.py", "single_module", 70),
+        ({}, "flat_layout/pkg.py", "flat_layout.pkg", 836),
+    ]
+)
+def test_resolve_class(tmp_path, package_dir, file, module, return_value):
+    files = {file: f"class Custom:\n    def testing(self): return {return_value}"}
+    write_files(files, tmp_path)
+    cls = expand.resolve_class(f"{module}.Custom", package_dir, tmp_path)
+    assert cls().testing() == return_value
 
 
 @pytest.mark.parametrize(