add testcases for --python with --local-only

src/pipdeptree/_discovery.py

@@ -25,17 +25,16 @@ def get_installed_distributions(
     if user_only:
         original_dists = distributions(path=[site.getusersitepackages()])
     elif using_custom_interpreter:
-        # We query the interpreter directly to get the `path` which is used by distributions(),
-        # so we can search the customer dists with it.
-        # If --python and --local-only are given at the same time, it means the dists only in
-        # customer's env are needed. (.e.g --system-site-packages is given when creating venv)
+        # We query the interpreter directly to get its `sys.path` list to be used by `distributions()`.
+        # If --python and --local-only are given, we ensure that we are only using paths associated to the
+        # interpreter's environment.
         if local_only:
-            args = "import sys, site; print(site.getsitepackages([sys.prefix]))"
+            cmd = "import sys, site; print(site.getsitepackages([sys.prefix]))"
         else:
-            args = "import sys; print(sys.path)"
+            cmd = "import sys; print(sys.path)"
 
-        cmd = [str(py_path), "-c", args]
-        result = subprocess.run(cmd, stdout=subprocess.PIPE, check=False)  # noqa: S603
+        args = [str(py_path), "-c", cmd]
+        result = subprocess.run(args, stdout=subprocess.PIPE, check=False)  # noqa: S603
         original_dists = distributions(path=ast.literal_eval(result.stdout.decode("utf-8")))
     elif local_only and in_venv:
         venv_site_packages = site.getsitepackages([sys.prefix])

tests/test_non_host.py

@@ -39,3 +39,30 @@ def test_custom_interpreter(
     if sys.version_info >= (3, 12):
         expected -= {"setuptools", "wheel"}
     assert found == expected, out
+
+
+def test_custom_interpreter_with_local_only(
+    tmp_path: Path,
+    monkeypatch: pytest.MonkeyPatch,
+    capfd: pytest.CaptureFixture[str],
+) -> None:
+    venv_path = str(tmp_path / "venv")
+
+    result = virtualenv.cli_run([venv_path, "--system-site-packages", "--activators", ""])
+
+    cmd = ["", f"--python={result.creator.exe}", "--local-only"]
+    monkeypatch.setattr(sys, "prefix", venv_path)
+    monkeypatch.setattr(sys, "argv", cmd)
+    main()
+    out, _ = capfd.readouterr()
+    found = {i.split("==")[0] for i in out.splitlines()}
+    implementation = python_implementation()
+    if implementation == "CPython":
+        expected = {"pip", "setuptools", "wheel"}
+    elif implementation == "PyPy":  # pragma: no cover
+        expected = {"cffi", "greenlet", "pip", "readline", "setuptools", "wheel"}  # pragma: no cover
+    else:
+        raise ValueError(implementation)  # pragma: no cover
+    if sys.version_info >= (3, 12):
+        expected -= {"setuptools", "wheel"}  # pragma: no cover
+    assert found == expected, out