Fix backward compatibility for renamed exception classes

Resolves GitHub issue #220 by adding backward compatibility aliases
for exception classes that were renamed in commit fdd69b1 to follow
PEP8 naming conventions.

Changes:
- Add RTSLibALUANotSupported alias for RTSLibALUANotSupportedError
- Add RTSLibNotInCFS alias for RTSLibNotInCFSError
- Export both old and new names in __all__
- Add comprehensive unit tests for backward compatibility

This restores compatibility with external projects like targetd that
depend on the original exception names while maintaining the new
PEP8-compliant names.

Author: guoguojenna

rtslib/__init__.py

@@ -38,32 +38,36 @@
     UserBackedStorageObject,
 )
 from .utils import (
+    RTSLibALUANotSupported,  # Backward compatibility alias
     RTSLibALUANotSupportedError,
     RTSLibBrokenLink,
     RTSLibError,
+    RTSLibNotInCFS,  # Backward compatibility alias
     RTSLibNotInCFSError,
 )
 
 __all__ = [
-    "RTSRoot",
-    "RTSLibError",
-    "RTSLibBrokenLink",
-    "RTSLibNotInCFSError",
-    "RTSLibALUANotSupportedError",
     "LUN",
-    "MappedLUN",
-    "NodeACL",
-    "NetworkPortal",
     "TPG",
-    "Target",
-    "NodeACLGroup",
-    "MappedLUNGroup",
+    "ALUATargetPortGroup",
+    "BlockStorageObject",
     "FabricModule",
     "FileIOStorageObject",
-    "BlockStorageObject",
+    "MappedLUN",
+    "MappedLUNGroup",
+    "NetworkPortal",
+    "NodeACL",
+    "NodeACLGroup",
     "PSCSIStorageObject",
     "RDMCPStorageObject",
-    "UserBackedStorageObject",
+    "RTSLibALUANotSupported",  # Backward compatibility alias
+    "RTSLibALUANotSupportedError",
+    "RTSLibBrokenLink",
+    "RTSLibError",
+    "RTSLibNotInCFS",  # Backward compatibility alias
+    "RTSLibNotInCFSError",
+    "RTSRoot",
     "StorageObjectFactory",
-    "ALUATargetPortGroup",
+    "Target",
+    "UserBackedStorageObject",
 ]

rtslib/utils.py

@@ -53,6 +53,13 @@ class RTSLibNotInCFSError(RTSLibError):
     object that does not exist.
     '''
 
+
+# Backward compatibility aliases for the old exception names
+# These were renamed in commit fdd69b1 to follow PEP8 naming conventions
+# but broke backward compatibility. Keep the old names as aliases.
+RTSLibALUANotSupported = RTSLibALUANotSupportedError
+RTSLibNotInCFS = RTSLibNotInCFSError
+
 def fwrite(path, string):
     '''
     This function writes a string to a file, and takes care of

tests/__init__.py

@@ -0,0 +1 @@
+# Test package for rtslib-fb

tests/test_backward_compatibility.py

@@ -0,0 +1,107 @@
+"""
+Unit tests for backward compatibility of renamed exception classes.
+
+Tests that the old exception names from before commit fdd69b1 still work
+to maintain compatibility with external projects like targetd.
+"""
+
+import pytest
+
+
+class TestBackwardCompatibility:
+    """Test backward compatibility for renamed exception classes."""
+
+    def test_old_exception_names_exist(self):
+        """Test that old exception names are still available in rtslib module."""
+        import rtslib
+
+        # Test that old names exist
+        assert hasattr(rtslib, 'RTSLibALUANotSupported')
+        assert hasattr(rtslib, 'RTSLibNotInCFS')
+
+    def test_new_exception_names_exist(self):
+        """Test that new PEP8-compliant exception names exist."""
+        import rtslib
+
+        # Test that new names exist
+        assert hasattr(rtslib, 'RTSLibALUANotSupportedError')
+        assert hasattr(rtslib, 'RTSLibNotInCFSError')
+
+    def test_exception_aliases_point_to_same_class(self):
+        """Test that old and new names refer to the same classes."""
+        import rtslib
+
+        assert rtslib.RTSLibALUANotSupported is rtslib.RTSLibALUANotSupportedError
+        assert rtslib.RTSLibNotInCFS is rtslib.RTSLibNotInCFSError
+
+    def test_aliases_in_module_all(self):
+        """Test that both old and new names are exported in __all__."""
+        import rtslib
+
+        assert 'RTSLibALUANotSupported' in rtslib.__all__
+        assert 'RTSLibNotInCFS' in rtslib.__all__
+        assert 'RTSLibALUANotSupportedError' in rtslib.__all__
+        assert 'RTSLibNotInCFSError' in rtslib.__all__
+
+    def test_exception_inheritance(self):
+        """Test that all exceptions inherit from RTSLibError."""
+        import rtslib
+
+        assert issubclass(rtslib.RTSLibALUANotSupported, rtslib.RTSLibError)
+        assert issubclass(rtslib.RTSLibNotInCFS, rtslib.RTSLibError)
+        assert issubclass(rtslib.RTSLibALUANotSupportedError, rtslib.RTSLibError)
+        assert issubclass(rtslib.RTSLibNotInCFSError, rtslib.RTSLibError)
+
+    def test_raise_and_catch_old_alua_exception(self):
+        """Test raising and catching RTSLibALUANotSupported."""
+        import rtslib
+
+        with pytest.raises(rtslib.RTSLibALUANotSupported):
+            raise rtslib.RTSLibALUANotSupported("Test ALUA exception")
+
+    def test_raise_and_catch_old_cfs_exception(self):
+        """Test raising and catching RTSLibNotInCFS."""
+        import rtslib
+
+        with pytest.raises(rtslib.RTSLibNotInCFS):
+            raise rtslib.RTSLibNotInCFS("Test CFS exception")
+
+    def test_cross_compatibility_alua_exception(self):
+        """Test that new exception can be caught with old name."""
+        import rtslib
+
+        with pytest.raises(rtslib.RTSLibALUANotSupported):
+            raise rtslib.RTSLibALUANotSupportedError("Test exception")
+
+    def test_cross_compatibility_cfs_exception(self):
+        """Test that new exception can be caught with old name."""
+        import rtslib
+
+        with pytest.raises(rtslib.RTSLibNotInCFS):
+            raise rtslib.RTSLibNotInCFSError("Test exception")
+
+    def test_old_exception_can_be_caught_with_new_name(self):
+        """Test that old exception name can be caught with new name."""
+        import rtslib
+
+        with pytest.raises(rtslib.RTSLibALUANotSupportedError):
+            raise rtslib.RTSLibALUANotSupported("Test exception")
+
+        with pytest.raises(rtslib.RTSLibNotInCFSError):
+            raise rtslib.RTSLibNotInCFS("Test exception")
+
+    def test_exception_messages_preserved(self):
+        """Test that exception messages work correctly with both names."""
+        import rtslib
+
+        test_message = "Custom error message"
+
+        try:
+            raise rtslib.RTSLibALUANotSupported(test_message)
+        except rtslib.RTSLibALUANotSupportedError as e:
+            assert str(e) == test_message
+
+        try:
+            raise rtslib.RTSLibNotInCFS(test_message)
+        except rtslib.RTSLibNotInCFSError as e:
+            assert str(e) == test_message