fix: narrow file picker data fallback errors (#146)

* fix: narrow file picker data fallback errors

* test: cover file picker fallback and resolver failures

---------

Co-authored-by: Peter Corke <peter.i.corke@gmail.com>

Author: RoboX2020

src/machinevisiontoolbox/base/imageio.py

@@ -54,7 +54,7 @@ def _pick_imagefile() -> Path:
     """
     try:
         initialdir = mvtb_path_to_datafile("images")
-    except Exception:
+    except (ModuleNotFoundError, ValueError):
         initialdir = Path.home()
 
     try:

tests/base/test_file_picker.py

@@ -0,0 +1,48 @@
+"""The file picker only falls back for unavailable toolbox data."""
+
+from pathlib import Path
+from types import SimpleNamespace
+from unittest.mock import Mock
+
+import pytest
+
+from machinevisiontoolbox.base import imageio
+
+
+@pytest.fixture
+def picker(monkeypatch):
+    dialog = Mock(return_value="selected.png")
+    root = Mock()
+    tk = SimpleNamespace(
+        Tk=Mock(return_value=root), filedialog=SimpleNamespace(askopenfilename=dialog)
+    )
+    monkeypatch.setitem(__import__("sys").modules, "tkinter", tk)
+    return dialog, root
+
+
+@pytest.mark.parametrize(
+    "error", [ModuleNotFoundError("mvtbdata"), ValueError("missing images")]
+)
+def test_missing_data_uses_home(monkeypatch, picker, error):
+    monkeypatch.setattr(imageio, "mvtb_path_to_datafile", Mock(side_effect=error))
+    dialog, root = picker
+    assert imageio._pick_imagefile() == Path("selected.png")
+    assert dialog.call_args.kwargs["initialdir"] == str(Path.home())
+    root.destroy.assert_called_once()
+
+
+def test_data_directory_is_used(monkeypatch, picker, tmp_path):
+    monkeypatch.setattr(imageio, "mvtb_path_to_datafile", Mock(return_value=tmp_path))
+    dialog, _ = picker
+    assert imageio._pick_imagefile() == Path("selected.png")
+    assert dialog.call_args.kwargs["initialdir"] == str(tmp_path)
+
+
+@pytest.mark.parametrize(
+    "error", [RuntimeError("broken resolver"), KeyboardInterrupt()]
+)
+def test_unexpected_resolver_errors_propagate(monkeypatch, picker, error):
+    monkeypatch.setattr(imageio, "mvtb_path_to_datafile", Mock(side_effect=error))
+    with pytest.raises(type(error)):
+        imageio._pick_imagefile()
+    picker[0].assert_not_called()