vLLM/vllm/entrypoints/openai/tool_parsers/pythonic_tool_parser.py

# SPDX-License-Identifier: Apache-2.0

import ast
import json
import re
from typing import Any, Sequence, Tuple, Union

from transformers import PreTrainedTokenizerBase

from vllm.entrypoints.openai.protocol import (ChatCompletionRequest,
                                              DeltaFunctionCall, DeltaMessage,
                                              DeltaToolCall,
                                              ExtractedToolCallInformation,
                                              FunctionCall, ToolCall)
from vllm.entrypoints.openai.tool_parsers.abstract_tool_parser import (
    ToolParser, ToolParserManager)
from vllm.logger import init_logger

logger = init_logger(__name__)


class _UnexpectedAstError(Exception):
    pass


@ToolParserManager.register_module("pythonic")
class PythonicToolParser(ToolParser):
    """
    Tool call parser for models that produce tool calls in a pythonic style,
    such as Llama 3.2 models.

    Used when --enable-auto-tool-choice --tool-call-parser pythonic are all set
    """
    # TODO(mdepinet): Possible future improvements:
    #   1. Support text + tools separated by either <|python_tag|> or \n\n
    #   2. Support tools outside of a list (or separated by a semicolon).
    #      This depends on item 1 for consistent streaming.
    # Neither of these are necessary for e.g. ToolACE, but both would help make
    # Llama3.2 models more reliable.

    TOOL_CALL_REGEX = re.compile(
        r"\[([a-zA-Z]+\w*\(([a-zA-Z]+\w*=.*,\s*)*([a-zA-Z]+\w*=.*\s)?\),\s*)*([a-zA-Z]+\w*\(([a-zA-Z]+\w*=.*,\s*)*([a-zA-Z]+\w*=.*\s*)?\)\s*)+\]",
        re.DOTALL)

    def __init__(self, tokenizer: PreTrainedTokenizerBase):
        super().__init__(tokenizer)

    # Rename for readability. This is NOT a tool id.
    @property
    def current_tool_index(self) -> int:
        return self.current_tool_id

    @current_tool_index.setter
    def current_tool_index(self, value: int) -> None:
        self.current_tool_id = value

    def extract_tool_calls(
            self, model_output: str,
            request: ChatCompletionRequest) -> ExtractedToolCallInformation:
        """
        Extract the tool calls from a complete model response.
        """

        if not (self.TOOL_CALL_REGEX.match(model_output)):
            return ExtractedToolCallInformation(tools_called=False,
                                                tool_calls=[],
                                                content=model_output)

        try:
            module = ast.parse(model_output)
            parsed = getattr(module.body[0], "value", None)
            if isinstance(parsed, ast.List) and all(
                    isinstance(e, ast.Call) for e in parsed.elts):
                return ExtractedToolCallInformation(
                    tools_called=True,
                    tool_calls=[
                        _handle_single_tool(e)  # type: ignore
                        for e in parsed.elts
                    ],
                    content=None)
            else:
                raise _UnexpectedAstError(
                    "Tool output must be a list of function calls")
        except Exception:
            logger.exception("Error in extracting tool call from response.")
            # Treat as regular text
            return ExtractedToolCallInformation(tools_called=False,
                                                tool_calls=[],
                                                content=model_output)

    def extract_tool_calls_streaming(
        self,
        previous_text: str,
        current_text: str,
        delta_text: str,
        previous_token_ids: Sequence[int],
        current_token_ids: Sequence[int],
        delta_token_ids: Sequence[int],
        request: ChatCompletionRequest,
    ) -> Union[DeltaMessage, None]:

        if not current_text.startswith("["):
            return DeltaMessage(content=delta_text)

        try:
            valid_and_added_text = _make_valid_python(current_text)
            if valid_and_added_text is None:
                return None
            valid_text, added_text = valid_and_added_text

            module = ast.parse(valid_text)
            parsed = getattr(module.body[0], "value", None)
            if not isinstance(parsed, ast.List) or not all(
                    isinstance(e, ast.Call) for e in parsed.elts):
                raise _UnexpectedAstError(
                    "Tool output must be a list of function calls")
            tool_calls = [
                _handle_single_tool(e)  # type: ignore
                for e in parsed.elts
            ]

            tool_deltas = []
            for index, new_call in enumerate(tool_calls):
                if index < self.current_tool_index:
                    continue

                self.current_tool_index = index
                if len(self.streamed_args_for_tool) == index:
                    self.streamed_args_for_tool.append("")

                new_call_complete = index < len(
                    tool_calls) - 1 or ")]" not in added_text
                if new_call_complete:
                    self.current_tool_index += 1

                withheld_suffix = (added_text[:-2]
                                   if not new_call_complete else "")
                if not new_call_complete and added_text[-2] == ")":
                    # Function call is incomplete. Withhold the closing bracket.
                    withheld_suffix = withheld_suffix + "}"
                # Strings get single quotes in the model-produced string.
                # JSON requires double quotes.
                withheld_suffix = withheld_suffix.replace("'", '"')
                delta = _compute_tool_delta(self.streamed_args_for_tool[index],
                                            new_call, index, withheld_suffix)

                if delta is not None:
                    tool_deltas.append(delta)
                    if (delta.function is not None
                            and delta.function.arguments is not None):
                        self.streamed_args_for_tool[
                            index] += delta.function.arguments

            # HACK: serving_chat.py inspects the internal state of tool parsers
            # when determining it's final streaming delta, automatically
            # adding autocompleted JSON.
            # These two lines avoid that nonsense while ensuring finish_reason
            # is set to tool_calls when at least one tool is called.
            if tool_deltas and not self.prev_tool_call_arr:
                self.prev_tool_call_arr = [{"arguments": {}}]

            if tool_deltas:
                return DeltaMessage(tool_calls=tool_deltas)
            elif not added_text and self.current_tool_id > 0:
                # Return an empty DeltaMessage once the tool calls are all done
                # so that finish_reason gets set.
                return DeltaMessage(content='')
            else:
                return None
        except Exception:
            logger.exception("Error trying to handle streaming tool call.")
            logger.debug(
                "Skipping chunk as a result of tool streaming extraction "
                "error")
            return None


def _get_parameter_value(val: ast.expr) -> Any:
    if isinstance(val, ast.Constant):
        return val.value
    elif isinstance(val, ast.Dict):
        if not all(isinstance(k, ast.Constant) for k in val.keys):
            raise _UnexpectedAstError(
                "Dict tool call arguments must have literal keys")
        return {
            k.value: _get_parameter_value(v)  # type: ignore
            for k, v in zip(val.keys, val.values)
        }
    elif isinstance(val, ast.List):
        return [_get_parameter_value(v) for v in val.elts]
    else:
        raise _UnexpectedAstError("Tool call arguments must be literals")


def _handle_single_tool(call: ast.Call) -> ToolCall:
    if not isinstance(call.func, ast.Name):
        raise _UnexpectedAstError("Invalid tool call name")
    function_name = call.func.id
    arguments = {}
    for keyword in call.keywords:
        arguments[keyword.arg] = _get_parameter_value(keyword.value)
    return ToolCall(type="function",
                    function=FunctionCall(name=function_name,
                                          arguments=json.dumps(arguments)))


def _make_valid_python(text: str) -> Union[Tuple[str, str], None]:
    bracket_stack = []
    for index, char in enumerate(text):
        if char in {"[", "(", "{"}:
            bracket_stack.append(char)
        elif char == "]":
            if not bracket_stack or bracket_stack.pop() != "[":
                raise _UnexpectedAstError("Mismatched square brackets")
        elif char == ")":
            if not bracket_stack or bracket_stack.pop() != "(":
                raise _UnexpectedAstError("Mismatched parentheses")
        elif char == "}":
            if not bracket_stack or bracket_stack.pop() != "{":
                raise _UnexpectedAstError("Mismatched curly braces")
        elif char in {"'", '"'}:
            if bracket_stack and bracket_stack[-1] == char:
                if index > 0 and text[index - 1] == "\\":
                    # Treat an escaped quote as a regular character
                    pass
                else:
                    bracket_stack.pop()
            elif bracket_stack and bracket_stack[-1] in {"'", '"'}:
                # Double quote within a single quote string or vice versa.
                pass
            else:
                bracket_stack.append(char)

    text = text.rstrip()
    if text.endswith("=") or text.endswith(":"):
        # Since we have no type information for this property/parameter value,
        # we can't fill in a valid value.
        return None
    if bracket_stack and bracket_stack[-1] == "{":
        trailing_dict_text = text[:text.rfind("{")]
        num_keys = trailing_dict_text.count(":")
        num_values = trailing_dict_text.count(",")
        if num_keys <= num_values:
            return None  # Incomplete property name within parameter value
    if bracket_stack and bracket_stack[-1] == "(":
        trailing_params_text = text[:text.rfind("(")]
        num_full_param_names = trailing_params_text.count("=")
        num_full_param_values = trailing_params_text.count(",")
        if num_full_param_names <= num_full_param_values:
            return None  # Incomplete parameter name
    if text.endswith(","):
        text = text[:-1]
    if bracket_stack and bracket_stack[-1] == "[" and not text.endswith(
            "[") and not text.endswith(")"):
        return None  # Incomplete function name

    added_text = ""
    for char in reversed(bracket_stack):
        if char == "[":
            added_text += "]"
        elif char == "(":
            added_text += ")"
        elif char == "{":
            added_text += "}"
        elif char == "'":
            added_text += "'"
        elif char == '"':
            added_text += '"'

    return text + added_text, added_text


def _compute_tool_delta(previously_sent_args: str, new_call: ToolCall,
                        index: int,
                        withheld_suffix: str) -> Union[DeltaToolCall, None]:
    new_call_args = new_call.function.arguments
    if withheld_suffix:
        assert new_call_args.endswith(withheld_suffix)
        new_call_args = new_call_args[:-len(withheld_suffix)]
    if not previously_sent_args:
        return DeltaToolCall(id=new_call.id,
                             index=index,
                             function=DeltaFunctionCall(
                                 name=new_call.function.name,
                                 arguments=new_call_args,
                             ))

    arg_diff = new_call_args[len(previously_sent_args):]
    return DeltaToolCall(
        id="", index=index, function=DeltaFunctionCall(
            arguments=arg_diff)) if arg_diff else None