gh-76991: Allow accessing the ags_gen and agt_gen attrs of async generators

[ZackerySpytz]

https://bugs.python.org/issue32810

• Issue: Expose ags_gen and agt_gen in asynchronous generators #76991

[asvetlov]

Looks very good, thanks!

Would you add a docs update to reflect new fields?

[bedevere-bot]

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[1st1]

Please don't merge this. I'm not sure i want them to be exposed.

[1st1]

We need to consider this carefully. Exposing these fields pins the current implementation and might prevent us from evolving it. It's also unclear if it's possible to implement this in PyPy et al

[asvetlov]

@1st1 thank you for sharing your worries.
I'll assign you to the PR.
You will decide, ok?

[csabella]

@1st1, just wondering if there is any update for this idea? Should the PR be closed so that the discussion can happen on the bug tracker first? Thanks!

[vxgmichel]

We need to consider this carefully. Exposing these fields pins the current implementation and might prevent us from evolving it. It's also unclear if it's possible to implement this in PyPy et al

Another way of fixing the issue described in bpo-32810 without adding extra field names is to expose async_generator.ag_* as async_generator_asend.cr_* (and async_generator_athrow.cr_*), i.e:

• async_generator_asend.cr_await -> async_generator_asend.ags_gen.ag_await
• async_generator_asend.cr_code -> async_generator_asend.ags_gen.ag_code
• async_generator_asend.cr_frame -> async_generator_asend.ags_gen.ag_frame
• async_generator_asend.cr_running -> async_generator_asend.ags_gen.ag_running
• async_generator_athrow.cr_await -> async_generator_athrow.agt_gen.ag_await
• async_generator_athrow.cr_code -> async_generator_athrow.agt_gen.ag_code
• async_generator_athrow.cr_frame -> async_generator_athrow.agt_gen.ag_frame
• async_generator_athrow.cr_running -> async_generator_athrow.agt_gen.ag_running

Retrieving the stack can then be implemented by simply walking up the chain of coroutines using cr_await and cr_frame. This would work transparently whether the stack contains async generators or not.

[iritkatriel]

https://bugs.python.org/issue32810 is closed. What is the status of this PR?

[erlend-aasland]

I fixed the merge conflicts, but the tests are failing all over the place. It looks to me the assumptions in the test in 6024d01 from 2018 won't hold in 2023.

[gvanrossum]

I am just closing this. In 2018 @1st1 didn't like the idea of exposing these fields. Here we are 6 years later and the only reason we're back looking at this is that someone decided to audit the OP's PRs.