fix(LoadImage): raise OptionalImportError when user-specified reader is not installed

monai/transforms/io/array.py

@@ -210,10 +210,10 @@ def __init__(
                     the_reader = look_up_option(_r.lower(), SUPPORTED_READERS)
                 try:
                     self.register(the_reader(*args, **kwargs))
-                except OptionalImportError:
-                    warnings.warn(
+                except OptionalImportError as e:
+                    raise OptionalImportError(
                         f"required package for reader {_r} is not installed, or the version doesn't match requirement."
-                    )
+                    ) from e
                 except TypeError:  # the reader doesn't have the corresponding args/kwargs
                     warnings.warn(f"{_r} is not supported with the given parameters {args} {kwargs}.")
                     self.register(the_reader())

tests/data/test_init_reader.py

@@ -15,6 +15,7 @@
 
 from monai.data import ITKReader, NibabelReader, NrrdReader, NumpyReader, PILReader, PydicomReader
 from monai.transforms import LoadImage, LoadImaged
+from monai.utils import OptionalImportError
 from tests.test_utils import SkipIfNoModule
 
 
@@ -26,8 +27,13 @@ def test_load_image(self):
         self.assertIsInstance(instance2, LoadImage)
 
         for r in ["NibabelReader", "PILReader", "ITKReader", "NumpyReader", "NrrdReader", "PydicomReader", None]:
-            inst = LoadImaged("image", reader=r)
-            self.assertIsInstance(inst, LoadImaged)
+            with self.subTest(reader=r):
+                try:
+                    inst = LoadImaged("image", reader=r)
+                    self.assertIsInstance(inst, LoadImaged)
+                except OptionalImportError:
+                    if r is None:
+                        self.fail("LoadImaged(reader=None) should not raise OptionalImportError.")
 
     @SkipIfNoModule("nibabel")
     @SkipIfNoModule("cupy")

tests/transforms/test_load_image.py

@@ -498,5 +498,24 @@ def test_correct(self, input_param, expected_shape, track_meta):
             self.assertFalse(hasattr(r, "affine"))
 
 
+class TestLoadImageReaderNotInstalled(unittest.TestCase):
+    """Tests that LoadImage raises when a user-specified reader's package is not installed."""
+
+    def test_raises_when_user_specified_reader_not_installed(self):
+        """Test LoadImage raises OptionalImportError for a missing user-specified reader.
+
+        Raises:
+            OptionalImportError: when the package required by the specified reader is not installed.
+        """
+        from unittest.mock import patch
+
+        from monai.utils import OptionalImportError
+
+        # Patch ITKReader.__init__ to simulate the package not being installed
+        with patch("monai.data.image_reader.ITKReader.__init__", side_effect=OptionalImportError("itk not installed")):
+            with self.assertRaisesRegex(OptionalImportError, "itk not installed|required package for reader ITKReader"):
+                LoadImage(reader="ITKReader")
+
+
 if __name__ == "__main__":
     unittest.main()