Add test for exclusion expectation. Ref #1650.

setuptools/tests/test_sdist.py

@@ -463,6 +463,22 @@ class TestSdistTest:
         manifest = cmd.filelist.files
         assert 'pyproject.toml' in manifest
 
+    def test_pyproject_toml_excluded(self):
+        """
+        Check that pyproject.toml can excluded even if present
+        """
+        open(os.path.join(self.temp_dir, 'pyproject.toml'), 'w').close()
+        with open('MANIFEST.in', 'w') as mts:
+            print('exclude pyproject.toml', file=mts)
+        dist = Distribution(SETUP_ATTRS)
+        dist.script_name = 'setup.py'
+        cmd = sdist(dist)
+        cmd.ensure_finalized()
+        with quiet():
+            cmd.run()
+        manifest = cmd.filelist.files
+        assert 'pyproject.toml' not in manifest
+
 
 def test_default_revctrl():
     """