Print resolved interpreter when using env detection

src/pipdeptree/__main__.py

@@ -26,7 +26,9 @@ def main(args: Sequence[str] | None = None) -> None | int:
     warning_printer.warning_type = options.warn
 
     if options.python == "auto":
-        options.python = detect_active_interpreter()
+        resolved_path = detect_active_interpreter()
+        options.python = resolved_path
+        print(f"Resolved Python: [{resolved_path}]", file=sys.stderr)  # noqa: T201
 
     pkgs = get_installed_distributions(
         interpreter=options.python, local_only=options.local_only, user_only=options.user_only

tests/test_detect_env.py

@@ -52,3 +52,17 @@ def test_detect_active_interpreter_non_existent_path(
 
     with pytest.raises(SystemExit):
         detect_active_interpreter()
+
+
+def test_detect_active_interpreter_log_resolved(
+    tmp_path: Path, mocker: MockFixture, capsys: pytest.CaptureFixture[str]
+) -> None:
+    mocker.patch("pipdeptree._detect_env.os.environ", {"VIRTUAL_ENV": str(tmp_path)})
+    mocker.patch("pipdeptree._detect_env.Path.exists", return_value=True)
+
+    actual_path = detect_active_interpreter()
+
+    captured = capsys.readouterr()
+
+    assert actual_path.startswith(str(tmp_path))
+    assert f"Resolved Python: [{tmp_path!s}" in captured.out