refactor(tool call): Fix BaseFormatDetector tool_index issue and refactor parse_streaming_increment (#6715)

python/sglang/srt/function_call/utils.py

@@ -18,6 +18,23 @@ def _find_common_prefix(s1: str, s2: str) -> str:
 
 
 def _partial_json_loads(input_str: str, flags: Allow) -> Tuple[Any, int]:
+    """
+    Parse incomplete or partial JSON strings commonly encountered during streaming.
+
+    Args:
+        input_str (str): The potentially incomplete JSON string to parse.
+        flags (Allow): Bitwise flags controlling what types of partial data are allowed.
+            Common flags include:
+            - Allow.STR: Allow partial strings (e.g., '"hello wo' -> 'hello wo')
+            - Allow.OBJ: Allow partial objects (e.g., '{"key":' -> {'key': None})
+            - Allow.ARR: Allow partial arrays (e.g., '[1, 2,' -> [1, 2])
+            - Allow.ALL: Allow all types of partial data
+
+    Returns:
+        Tuple[Any, int]: A tuple containing:
+            - parsed_object: The Python object parsed from the JSON
+            - consumed_length: Number of characters consumed from input_str
+    """
     try:
         return (partial_json_parser.loads(input_str, flags), len(input_str))
     except JSONDecodeError as e: