fix: don't yield final result an extra time

Author: petersli

pydantic_ai_slim/pydantic_ai/result.py

@@ -114,16 +114,19 @@ async def stream_text(self, *, delta: bool = False, debounce_by: float | None =
             async for text in self._stream_response_text(delta=True, debounce_by=debounce_by):
                 yield text
         else:
-            text: str | None = None
+            last_text: str | None = None
             async for text in self._stream_response_text(delta=False, debounce_by=debounce_by):
                 for validator in self._output_validators:
                     text = await validator.validate(text, self._run_ctx, partial=True)  # pragma: no cover
+                last_text = text
                 yield text
 
-            if text is not None:
+            if last_text is not None:
+                validated_text = last_text
                 for validator in self._output_validators:
-                    text = await validator.validate(text, self._run_ctx)
-                yield text
+                    validated_text = await validator.validate(validated_text, self._run_ctx)
+                if validated_text != last_text:
+                    yield validated_text
 
     # TODO (v2): Drop in favor of `response` property
     def get(self) -> _messages.ModelResponse: