Accessing one lazily imported submodule (`lazy import pkg.a`) also imports a later imported `pkg.b`

[msullivan]

Bug report

Bug description:

If we do a lazy import of two submodules in the same package tree (like pkg.a and pkg.b), then accessing pkg.a will cause pkg.b to get imported first. I think this is because pkg gets bound specifically to a lazy_import object for pkg.b. (In fact, just accessing pkg also imports pkg.b).

main.py:

lazy import pkg.a
lazy import pkg.b

print(globals()['pkg'])  # <lazy_import 'pkg.b'>

pkg.a  # triggers import of pkg (of course), pkg.b (sketchy!!), pkg.a (of course)

pkg/
├── __init__.py   # print("pkg")
├── a.py          # print("pkg.a")
└── b.py          # print("pkg.b")

This prints:

<lazy_import 'pkg.b'>
pkg
pkg.b
pkg.a

CPython versions tested on:

3.15

Operating systems tested on:

Linux

Linked PRs

• gh-158140: Do not eagerly import sibling submodules on lazy import #158491
• gh-158140: Resolve lazily imported sibling submodules independently #158521