Replace tenacity.retry with our own decorator

[ichard26]

Tenacity is a 1600+ LOC dependency which is only used for a convenient @retry decorator... which is used a grand total of two times. This is a lot of code for what can be trivially reimplemented by us.

This also incidentally improves startup performance as tenacity imports asyncio which is expensive and unnecessary for us.

Resolves #10822.

[ichard26]

CI is failing as typing-extensions doesn't support Python 3.13 (at least not for ParamSpec). Jelle informed me that there should be a new release fixing these issues soon, though. I'm not very happy with the jankiness of my unit tests, so I think I'll rewrite them. I won't have time until tomorrow, if not the weekend though.

[notatallshaw]

As you have no runtime need for these type hints, a workaround is to put the type annotation constructions behind an if TYPE_CHECKING and then use string annotations or from __future__ import annotations,

[ichard26]

I literally contribute to mypyc and yet I somehow completely forgot about that trick. Gosh, that's what I get for writing code when I'm too tired. Thanks for the reminder!

(*) I'm not sure if the use of from __future__ import annotations is approved for this codebase. IIRC the maintainers wanted to wait until the situation between annotations and co_annotations was resolved before making a decision.

[uranusjr]

This seems simple enough, but do we have analysis on how the decorator compares to tenacity’s implementation? Are there edge cases?

[ichard26]

This seems simple enough, but do we have analysis on how the decorator compares to tenacity’s implementation? Are there edge cases?

I did briefly read through tenacity's source code to get a feel for how it works (especially in regards to the time limit), but I haven't examined it carefully. However, I have written a decent set of unit tests for my decorator. Notably, they still all pass when testing tenacity's @retry implementation. I tested this by commenting out the pip._internal import and adding this near the top of the test module:

from tenacity import wait_fixed, stop_after_delay as _stop_after_delay, retry as _retry

def retry(wait, stop_after_delay):
    return _retry(wait=wait_fixed(wait), stop=_stop_after_delay(stop_after_delay), reraise=True)

I can take a closer look at tenacity's implementation if you'd like, but I think these tests demonstrate that the two decorators are functionally equivalent in the areas that matter.

[ichard26]

Windows' such a joy, sigh ✨

[ichard26]

This is reasonably close to be ready for review. I do want to make some more minor changes to the tests, but CI is going to keep failing until #12732 is merged.

[ichard26]

Oh for goodness sake, Python 3.8's Callable does not support "P" as the argument type. I still need the typing-extensions upgrade then.

[ichard26]

Alright, this should be ready for review now that #12804 is in. I know this patch looks big, but the vast majority of the additions is from the unit tests. The retry utility altogether is only 41 lines long.

See also #12705 (comment) for commentary on the equivalency between this new decorator and @tenacity.retry.