don't load site-packages in pdm run

Close #708

news/708.feature.md

@@ -0,0 +1 @@
+Isolate the project environment with system site packages in `pdm run`, but keep them seen when PEP 582 is enabled.

pdm/cli/commands/run.py

@@ -59,6 +59,8 @@ def _run_command(
                 "PDM_PROJECT_ROOT": str(project.root),
             }
         )
+        if not project_env.is_global:
+            os.environ["NO_SITE_PACKAGES"] = "1"
         if project_env.packages_path:
             os.environ.update({"PEP582_PACKAGES": str(project_env.packages_path)})
         if env_file:

pdm/pep582/sitecustomize.py

@@ -77,10 +77,11 @@ def main():
 
     # Second, add lib directories, ensuring .pth file are processed.
     site.addsitedir(libpath)
-    # Then add the removed path to the tail of the paths
-    known_paths.clear()
-    site.addusersitepackages(known_paths)
-    site.addsitepackages(known_paths)
+    if not os.getenv("NO_SITE_PACKAGES"):
+        # Then add the removed path to the tail of the paths
+        known_paths.clear()
+        site.addusersitepackages(known_paths)
+        site.addsitepackages(known_paths)
 
 
 main()

tests/cli/test_run.py

@@ -29,6 +29,16 @@ def test_pep582_launcher_for_python_interpreter(project, invoke):
     assert output.decode().strip() == "2.24.0"
 
 
+def test_pep582_with_system_site_packages(project, invoke):
+    env = os.environ.copy()
+    env.update({"PYTHONPATH": PEP582_PATH})
+    proc = subprocess.run([project.python.executable, "-c", "import click"], env=env)
+    assert proc.returncode == 0
+
+    result = invoke(["run", "python", "-c", "import click"], obj=project)
+    assert result.exit_code != 0
+
+
 def test_run_command_not_found(invoke):
     result = invoke(["run", "foobar"])
     assert "Command 'foobar' is not found on your PATH." in result.stderr

tests/conftest.py

@@ -251,6 +251,7 @@ def project_no_init(tmp_path, mocker):
     with temp_environ():
         os.environ.pop("VIRTUAL_ENV", None)
         os.environ.pop("PEP582_PACKAGES", None)
+        os.environ.pop("NO_SITE_PACKAGES", None)
         pythonpath = os.environ.pop("PYTHONPATH", "")
         pythonpath = remove_pep582_path_from_pythonpath(pythonpath)
         if pythonpath: