gh-83180: Made launcher treat shebang 'python' tags as low priority so that active virtual environments are preferred (GH-108101)

Lib/test/test_launcher.py

@@ -717,3 +717,25 @@ class TestLauncher(unittest.TestCase, RunPyMixin):
             f"{expect} arg1 {script}",
             data["stdout"].strip(),
         )
+
+    def test_shebang_command_in_venv(self):
+        stem = "python-that-is-not-on-path"
+
+        # First ensure that our test name doesn't exist, and the launcher does
+        # not match any installed env
+        with self.script(f'#! /usr/bin/env {stem} arg1') as script:
+            data = self.run_py([script], expect_returncode=103)
+
+        with self.fake_venv() as (venv_exe, env):
+            # Put a real Python (ourselves) on PATH as a distraction.
+            # The active VIRTUAL_ENV should be preferred when the name isn't an
+            # exact match.
+            env["PATH"] = f"{Path(sys.executable).parent};{os.environ['PATH']}"
+
+            with self.script(f'#! /usr/bin/env {stem} arg1') as script:
+                data = self.run_py([script], env=env)
+            self.assertEqual(data["stdout"].strip(), f"{venv_exe} arg1 {script}")
+
+            with self.script(f'#! /usr/bin/env {Path(sys.executable).stem} arg1') as script:
+                data = self.run_py([script], env=env)
+            self.assertEqual(data["stdout"].strip(), f"{sys.executable} arg1 {script}")