Modify tests to ensure $PYTHONPATH is given to the custom interpreter (#353)

Author: kemzeb

tests/test_non_host.py

@@ -23,11 +23,14 @@ def test_custom_interpreter(
     capfd: pytest.CaptureFixture[str],
     args_joined: bool,
 ) -> None:
-    result = virtualenv.cli_run([str(tmp_path / "venv"), "--activators", ""])
-    cmd = [sys.executable]
+    # Delete $PYTHONPATH so that it cannot be passed to the custom interpreter process (since we don't know what
+    # distribution metadata to expect when it's used).
+    monkeypatch.delenv("PYTHONPATH", False)
+
     monkeypatch.chdir(tmp_path)
+    result = virtualenv.cli_run([str(tmp_path / "venv"), "--activators", ""])
     py = str(result.creator.exe.relative_to(tmp_path))
-    cmd += [f"--python={result.creator.exe}"] if args_joined else ["--python", py]
+    cmd = ["", f"--python={result.creator.exe}"] if args_joined else ["", "--python", py]
     mocker.patch("pipdeptree._discovery.sys.argv", cmd)
     main()
     out, _ = capfd.readouterr()
@@ -69,3 +72,37 @@ def test_custom_interpreter_with_local_only(
     if sys.version_info >= (3, 12):
         expected -= {"setuptools", "wheel"}  # pragma: no cover
     assert found == expected, out
+
+
+def test_custom_interpreter_ensure_pythonpath_envar_is_honored(
+    tmp_path: Path,
+    mocker: MockerFixture,
+    monkeypatch: pytest.MonkeyPatch,
+    capfd: pytest.CaptureFixture[str],
+) -> None:
+    # ensures that we honor $PYTHONPATH when passing it to the custom interpreter process
+    venv_path = str(tmp_path / "venv")
+    result = virtualenv.cli_run([venv_path, "--activators", ""])
+
+    another_path = tmp_path / "another-path"
+    fake_dist = another_path / "foo-1.2.3.dist-info"
+    fake_dist.mkdir(parents=True)
+    fake_metadata = fake_dist / "METADATA"
+    with fake_metadata.open("w") as f:
+        f.write("Metadata-Version: 2.3\n" "Name: foo\n" "Version: 1.2.3\n")
+    cmd = ["", f"--python={result.creator.exe}"]
+    mocker.patch("pipdeptree._discovery.sys.argv", cmd)
+    monkeypatch.setenv("PYTHONPATH", str(another_path))
+    main()
+    out, _ = capfd.readouterr()
+    found = {i.split("==")[0] for i in out.splitlines()}
+    implementation = python_implementation()
+    if implementation == "CPython":
+        expected = {"foo", "pip", "setuptools", "wheel"}
+    elif implementation == "PyPy":  # pragma: cpython no cover
+        expected = {"foo", "cffi", "greenlet", "pip", "readline", "setuptools", "wheel"}
+    else:  # pragma: no cover
+        raise ValueError(implementation)
+    if sys.version_info >= (3, 12):  # pragma: >=3.12 cover
+        expected -= {"setuptools", "wheel"}
+    assert found == expected, out