Improve startup times in Complement test runs against workers, particularly in CPU-constrained environments.

[reivilibre]

Fixes #13051.

Should be more or less a step-by-step review, but it may be clear enough from the overall diff also, I don't know.

[richvdh]

looks pretty good to me! a couple of nits.

[richvdh]

I think this is redundant? __getattr__ is only called when a normal attribute lookup fails.

[reivilibre]

I thought the same, but I get

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<stdin>", line 30, in __getattr__
AttributeError: 'NoneType' object has no attribute '___install'

if I don't have that there. :/

[richvdh]

'NoneType' object has no attribute '___install'

.... that implies you're calling ___install on None ?

[reivilibre]

Oh, interesting, this isn't a problem if I only have one underscore as a prefix for the name. The docs don't seem to mention why this is, but oh well..

[reivilibre]

'NoneType' object has no attribute '___install'

.... that implies you're calling ___install on None ?

Yes, because that's how __getattr__ is implemented. The underlying, not-yet-installed reactor (None) doesn't have an ___install method.
According to what you + docs are saying, it shouldn't call __getattr__ because the class itself has a ___install

[reivilibre]

if you want to try at home:

from typing import Any

class A:
    def __init__(self) -> None:
        self.___reactor_target: Any = None

    def ___install(self, new_reactor: Any) -> None:
        self.___reactor_target = new_reactor

    def __getattr__(self, attr_name: str) -> Any:
        return getattr(self.___reactor_target, attr_name)


class B:
    def __init__(self) -> None:
        self.___reactor_target: Any = None

    def _install(self, new_reactor: Any) -> None:
        self.___reactor_target = new_reactor

    def __getattr__(self, attr_name: str) -> Any:
        return getattr(self.___reactor_target, attr_name)

then:

a = A()
a.___install(42) # <--- fails
print(a.conjugate())

compare to

b = B()
b._install(42)
print(b.conjugate())

[richvdh]

lgtm otherwise