Potential Asynchronous Context Confusion in `set_headers`

[nitish-yaddala]

Description

In the set_headers method, the code tries to detect if set_header is a coroutine using inspect.iscoroutinefunction and raises a RuntimeError if it detects an asynchronous function.

However, this behavior may confuse developers because:

• It does not offer a fallback mechanism (such as awaiting automatically if possible).
• The error message does not suggest a clear next step, such as using the set_headers_async method instead.

This could lead to confusion or misuse, especially in frameworks that rely heavily on asynchronous responses (e.g., FastAPI).

Affected Code

if inspect.iscoroutinefunction(set_header):
    raise RuntimeError(
        "Encountered asynchronous 'set_header' in synchronous context."
    )

Lines 242–245

Recommendation

• Improve the RuntimeError message to clearly advise the developer to use set_headers_async instead.
• Optionally enhance the logic to auto-detect an active asynchronous context and automatically handle it, for example:
  • Check if an event loop is running using asyncio.get_running_loop().
  • If yes, optionally raise a different, more helpful exception or adapt behavior accordingly.