How does a custom tool under BuiltinTool return files?

[guoshiqiufeng]

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1. Is this request related to a challenge you're experiencing? Tell me about your story.

I have implemented a FileTransferTool by myself , the current function will transfer the file to local, return file json, please ask how can I return the file list.

The code is as follows:

import base64
import logging
from mimetypes import guess_extension
from typing import Any, Union, Optional
from core.tools.entities.tool_entities import ToolInvokeMessage
from core.tools.tool.builtin_tool import BuiltinTool
from core.tools.entities.tool_entities import ToolInvokeMessage
from core.tools.tool_file_manager import ToolFileManager
from core.file.models import File, FileTransferMethod, FileType
from httpx import get

class FileTransferTool(BuiltinTool):
    def _invoke(
        self,
        user_id: str,
        tool_parameters: dict[str, Any],
    ) -> Union[ToolInvokeMessage, list[ToolInvokeMessage]]:
        """
        Decodes base64 content or downloads file from URL and saves it as a file.
        Handles both data URI prefix for base64 and regular URLs for downloading files.
        """
        file_content = tool_parameters.get("url", "").strip()
        if not file_content:
            return self.create_text_message("Invalid url or base64 content.")

        if self._is_base64(file_content):
            return self._process_base64(user_id, file_content)
        else:
            return self._process_url(user_id, file_content)

    def _is_base64(self, content: str) -> bool:
        """
        Check if the content is in base64 format by matching a common base64 pattern.
        """
        try:
            if content.startswith("data:"):
                return True
            base64.b64decode(content, validate=True)
            return True
        except Exception:
            return False

    def _process_base64(self, user_id: str, base64_content: str) -> ToolInvokeMessage:
        """
        Process the base64 content, extract MIME type, and save it as a file.
        """
        base64_content, mimetype = self._extract_mimetype_and_content(base64_content)
        file_binary = base64.b64decode(base64_content)
        return self._save_as_file(user_id, file_binary, mimetype)

    def _process_url(self, user_id: str, file_url: str) -> ToolInvokeMessage:
        """
        Download the file from the provided URL and save it as a file.
        """
        try:
            response = get(file_url)
            response.raise_for_status()
            file_binary = response.content
            mimetype = response.headers.get("Content-Type", "application/octet-stream")
            return self._save_as_file(user_id, file_binary, mimetype)
        except Exception as e:
            logging.exception(f"Failed to download file from {file_url}: {e}")
            return self.create_text_message(f"Error downloading file: {str(e)}")

    def _extract_mimetype_and_content(self, base64_content: str) -> tuple[str, str]:
        """
        Extracts MIME type from base64 content's data URI prefix and removes the prefix.
        """
        if base64_content.startswith("data:"):
            mime_type, base64_data = base64_content.split(",", 1)
            base64_content = base64_data
            mimetype = mime_type.split(";")[0].replace("data:", "")
        else:
            mimetype = "application/octet-stream"
        return base64_content, mimetype

    def get_tool_file_url(self, tool_file_id: str, extension: Optional[str]) -> str:
        return f'/files/tools/{tool_file_id}{extension or ".bin"}'

    def _save_as_file(self, user_id: str, file_binary: bytes, mimetype: str) -> ToolInvokeMessage:
        """
        Decodes base64 string and saves it using ToolFileManager, generating a unique filename.
        Returns detailed information about the saved file.
        """
        try:
            conversation_id = None

            tenant_id = self.runtime.tenant_id 
            tool_file = ToolFileManager.create_file_by_raw(
                user_id=user_id,
                tenant_id=tenant_id,
                conversation_id=conversation_id,
                file_binary=file_binary,
                mimetype=mimetype,
            )

            file_info = {
                "id": tool_file.id,
                "name": tool_file.name,
                "size": tool_file.size,
                "mimetype": tool_file.mimetype,
                "file_key": tool_file.file_key,
            }
            result = []

            result.append(self.create_file_message(tool_file))
            result.append(self.create_json_message(file_info))
            return result

        except Exception as e:
            logging.exception(f"Failed to decode base64 and save to file: {e}")
            return self.create_text_message(f"Error decoding file: {str(e)}")

2. Additional context or comments

No response

[guoshiqiufeng]

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