consider adding on_return and on_error transform functions to timer_decorator

[willkg]

I often want to decorate functions with timer_decorator, but want to provide different tags depending on the returned result or error.

What if we added on_return and on_error transform functions with defaults:

def on_return(tags, value, ret):
    return tags, value, ret

def on_error(tags, value, exc):
    return tags, value, exc

These would get called here after the function has completed:

markus/src/markus/main.py

Line 515 in a3a5db6

return fun(*args, **kwargs)

[willkg]

@jwhitlock Have you ever needed something like this?

[jwhitlock]

No, I haven't needed something like that, and I usually don't reach for timer_decorator

I've been using codetiming recently like this:

with Timer(logger=None) as something_timer:
    ret = do_something()
log_data = {
   something_s = round(something_timer.last, 3)
}
log.info("Ran something", extra=log_data)
markus.timing('ran.something', something_timer.last)

I can't really recommend my method or codetiming (main benefit - someone else maintains it). But usually, when I time something, I want to log it, not just send metrics.