fix: detect incompatible case_sensitive+preserve_case instances

g2p/mappings/utils.py

@@ -667,7 +667,7 @@ class _MappingModelDefinition(BaseModel):
     """List of case equivalencies for preserve_case that are not already in the Unicode standard"""
 
     preserve_case: bool = False
-    """Preserve source case in output"""
+    """Preserve source case in output (requires case_sensitive=False)"""
 
     escape_special: bool = False
     """Escape special characters in rules"""
@@ -731,7 +731,7 @@ def check_mapping_types(self) -> "_MappingModelDefinition":
             and not self.rules
             and self.rules_path is None
         ):
-            LOGGER.warn(
+            LOGGER.warning(
                 exceptions.MalformedMapping(
                     "You have to either specify some rules or a path to a file containing rules."
                 )
@@ -773,6 +773,15 @@ def validate_case_equivalencies(cls, v):
                 )
         return v
 
+    @model_validator(mode="after")
+    def validate_preserve_case(self):
+        """preserve_case=True requires case_sensitive=False"""
+        if self.preserve_case and self.case_sensitive:
+            raise exceptions.MalformedMapping(
+                "Sorry, preserve_case=True requires case_sensitive=False."
+            )
+        return self
+
     # TODO[pydantic]: We couldn't refactor the `validator`, please replace it by `field_validator` manually.
     # Check https://docs.pydantic.dev/dev-v2/migration/#changes-to-validators for more information.
     @validator("rules_path", "abbreviations_path", "alignments_path", pre=True)

g2p/tests/test_transducer.py

@@ -255,6 +255,9 @@ def test_case_preservation(self):
                 case_equivalencies={"λ": "\u2144\u2144\u2144"},
             )
 
+        with self.assertRaises(MalformedMapping):
+            _ = Mapping(rules=[], case_sensitive=True, preserve_case=True)
+
     def test_normalize_edges(self):
         # Remove non-deletion edges with the same index as deletions
         bad_edges = [