Add a test capturing the desired expectation, marked as xfail for now.

setuptools/tests/test_develop.py

@@ -3,6 +3,7 @@
 import os
 import sys
 import subprocess
+import pathlib
 import platform
 
 from setuptools.command import test
@@ -82,6 +83,18 @@ def test_console_scripts(self, tmpdir):
         cmd.run()
         # assert '0.0' not in foocmd_text
 
+    @pytest.mark.xfail(reason="legacy behavior retained for compatibility #4167")
+    def test_egg_link_filename(self):
+        settings = dict(
+            name='Foo $$$ Bar_baz-bing',
+        )
+        dist = Distribution(settings)
+        cmd = develop(dist)
+        cmd.ensure_finalized()
+        link = pathlib.Path(cmd.egg_link)
+        assert link.suffix == '.egg-link'
+        assert link.stem == 'Foo_Bar_baz_bing'
+
 
 class TestResolver:
     """