Add option to functools.update_wrapper()/@wraps to copy the coroutine flag

[srittau]

Feature or enhancement

Proposal:

This came up during #122088, where it was noted that @deprecated drops the coroutine flag of a function. @deprecated uses @wraps/update_wrapper internally. This was previously discussed in #100317, where it was suggested that the flag should be copied automatically. It was ultimately decided by @gvanrossum that this is dangerous, since wrappers might decide to convert from/to coroutines.

I propose to add a flag to update_wrapper() and @wraps to optionally copy the status:

• It's more convenient to use than using the boilerplate code mentioned in the previous issue. Especially since I would assume that most wrappers want to copy this status.
• Probably more important: This makes this problem and its solution discoverable. As the @deprecated example shows, most people probably don't think about this issue when creating a wrapper. By adding a flag to the API and the documentation, this problem will be mentioned and can be discovered by users of @wraps, either while reading the documentation, or when the IDE shows the availability of the flag.

Has this already been discussed elsewhere?

This is a minor feature, which does not need previous discussion elsewhere

Links to previous discussion of this feature:

No response