Decrease start-up time of editable-installed entry points on newer versions of Python

changelog.d/2194.change.rst

+Editable-installed entry points now load significantly faster on Python versions 3.8+.

setuptools/command/easy_install.py

@@ -2070,6 +2070,23 @@ class ScriptWriter:
     gui apps.
     """
 
+    try:
+        from importlib.metadata import distribution  # noqa: F401
+
+        template = textwrap.dedent(r"""
+            # EASY-INSTALL-ENTRY-SCRIPT: %(spec)r,%(group)r,%(name)r
+            __requires__ = %(spec)r
+            import re
+            import sys
+            from importlib.metadata import distribution
+
+            if __name__ == '__main__':
+                sys.argv[0] = re.sub(r'(-script\.pyw?|\.exe)?$', '', sys.argv[0])
+                for entry_point in distribution(%(spec)r).entry_points:
+                    if entry_point.group == %(group)r and entry_point.name == %(name)r:
+                        sys.exit(entry_point.load()())
+        """).lstrip()  # noqa: E501
+    except ImportError:
         template = textwrap.dedent(r"""
             # EASY-INSTALL-ENTRY-SCRIPT: %(spec)r,%(group)r,%(name)r
             __requires__ = %(spec)r
@@ -2082,7 +2099,7 @@ class ScriptWriter:
                 sys.exit(
                     load_entry_point(%(spec)r, %(group)r, %(name)r)()
                 )
-    """).lstrip()
+        """).lstrip()  # noqa: E501
 
     command_spec_class = CommandSpec
 

setuptools/tests/test_easy_install.py

@@ -71,6 +71,23 @@ class TestEasyInstallTest:
 
     def test_get_script_args(self):
         header = ei.CommandSpec.best().from_environment().as_header()
+        try:
+            from importlib.metadata import distribution  # noqa: F401
+
+            expected = header + DALS(r"""
+                # EASY-INSTALL-ENTRY-SCRIPT: 'spec','console_scripts','name'
+                __requires__ = 'spec'
+                import re
+                import sys
+                from importlib.metadata import distribution
+
+                if __name__ == '__main__':
+                    sys.argv[0] = re.sub(r'(-script\.pyw?|\.exe)?$', '', sys.argv[0])
+                    for entry_point in distribution('spec').entry_points:
+                        if entry_point.group == 'console_scripts' and entry_point.name == 'name':
+                            sys.exit(entry_point.load()())
+                """)  # noqa: E501
+        except ImportError:
             expected = header + DALS(r"""
                 # EASY-INSTALL-ENTRY-SCRIPT: 'spec','console_scripts','name'
                 __requires__ = 'spec'
@@ -84,6 +101,7 @@ class TestEasyInstallTest:
                         load_entry_point('spec', 'console_scripts', 'name')()
                     )
                 """)  # noqa: E501
+
         dist = FakeDist()
 
         args = next(ei.ScriptWriter.get_args(dist))