errors.py

# Copyright (c) Meta Platforms, Inc. and affiliates.
# All rights reserved.
#
# This source code is licensed under the BSD-style license found in the
# LICENSE file in the root directory of this source tree.

"""OpenAI-shaped API errors.

Raising these lets the server return a structured `{"error": {...}}` body with
the right HTTP status instead of dropping the connection.
"""

from typing import Optional


class APIError(Exception):
    def __init__(
        self, status: int, message: str, err_type: str, code: Optional[str] = None
    ):
        super().__init__(message)
        self.status = status
        self.message = message
        self.err_type = err_type
        self.code = code

    def body(self) -> dict:
        return {
            "error": {"message": self.message, "type": self.err_type, "code": self.code}
        }


class ContextLengthExceeded(APIError):
    def __init__(self, num_tokens: int, max_context: int, completion_tokens: int = 0):
        # completion_tokens > 0: the prompt fits but prompt + requested
        # max_tokens would run past the window — reject up front rather than
        # fail (or truncate) mid-generation.
        if completion_tokens > 0:
            message = (
                f"This model's maximum context length is {max_context} tokens. "
                f"However, you requested {num_tokens + completion_tokens} tokens "
                f"({num_tokens} in the messages, {completion_tokens} in the "
                f"completion). Please reduce the length of the messages or "
                f"completion."
            )
        else:
            message = (
                f"This model's maximum context length is {max_context} tokens, "
                f"but the request has {num_tokens} prompt tokens."
            )
        super().__init__(
            status=400,
            message=message,
            err_type="invalid_request_error",
            code="context_length_exceeded",
        )


class GenerationError(APIError):
    def __init__(self, detail: str):
        super().__init__(
            status=500, message=f"Generation failed: {detail}", err_type="server_error"
        )