[BugFix] Fix hermes tool parser output error stream arguments in some…

… cases (vllm-project#10395)

Signed-off-by: xiyuan lee <[email protected]>

vllm/entrypoints/openai/tool_parsers/hermes_tool_parser.py

@@ -190,8 +190,8 @@ def extract_tool_calls_streaming(
                 diff = self.prev_tool_call_arr[self.current_tool_id].get(
                     "arguments")
                 if diff:
-                    diff = json.dumps(diff).replace(
-                        self.streamed_args_for_tool[self.current_tool_id], "")
+                    diff = diff.encode('utf-8').decode('unicode_escape') if diff is str else diff
+                    diff = json.dumps(diff, ensure_ascii=False)[len(self.streamed_args_for_tool[self.current_tool_id]):]
                     logger.debug(
                         "Finishing tool and found diff that had not "
                         "been streamed yet: %s", diff)
@@ -307,22 +307,19 @@ def extract_tool_calls_streaming(
 
             # last case -- we have an update to existing arguments.
             elif cur_arguments and prev_arguments:
+                if isinstance(delta_text, str) and len(delta_text.rstrip())>=1 and delta_text.rstrip()[-1] == '}':
+                    delta_text = delta_text.rstrip()[:-1]
+
+                logger.debug("got diff %s", delta_text)
 
-                cur_args_json = json.dumps(cur_arguments)
-                prev_args_json = json.dumps(prev_arguments)
-                logger.debug("Searching for diff between\n%s", cur_args_json)
-                logger.debug("and\n%s", prev_args_json)
-                argument_diff = extract_intermediate_diff(
-                    cur_args_json, prev_args_json)
-                logger.debug("got argument diff %s", argument_diff)
                 delta = DeltaMessage(tool_calls=[
                     DeltaToolCall(index=self.current_tool_id,
                                   function=DeltaFunctionCall(
-                                      arguments=argument_diff).model_dump(
+                                      arguments=delta_text).model_dump(
                                           exclude_none=True))
                 ])
                 self.streamed_args_for_tool[self.current_tool_id] \
-                    += argument_diff
+                    += delta_text
 
             # handle saving the state for the current tool into
             # the "prev" list for use in diffing for the next iteration