AVRO-2921 Add Type Hints to avro.schema

lang/py/avro/__main__.py

@@ -161,9 +161,12 @@ def convert(value: str, field: avro.schema.Field) -> Union[int, float, str, byte
 
 
 def convert_union(value: str, field: avro.schema.Field) -> Union[int, float, str, bytes, bool, None]:
-    for name in (s.name for s in field.type.schemas):
+    if not isinstance(field.type, avro.schema.UnionSchema):
+        raise avro.errors.UsageError(f"Expected field.type to be a Union, but it was {field.type}")
+    # Casts to be fixed in AVRO-3798
+    for name in (cast(avro.schema.NamedSchema, s).name for s in field.type.schemas):
         try:
-            return convert(value, name)
+            return convert(value, cast(avro.schema.Field, name))
         except ValueError:
             continue
     raise avro.errors.UsageError("Exhausted Union Schema without finding a match")

lang/py/avro/protocol.py

@@ -215,10 +215,10 @@ def to_json(self, names: Optional[avro.name.Names] = None) -> "MessageObject":
             to_dump = MessageObject()
         except NameError:
             to_dump = {}
-        to_dump["request"] = self.request.to_json(names)
+        to_dump["request"] = cast(Sequence[Mapping[str, object]], self.request.to_json(names))
         to_dump["response"] = self.response.to_json(names)
         if self.errors:
-            to_dump["errors"] = self.errors.to_json(names)
+            to_dump["errors"] = cast(Optional[Sequence[str]], self.errors.to_json(names))
 
         return to_dump