Names that have been resolved are not consistently removed from sys.lazy_modules

Bug report

Bug description:

I'm slightly hesitant to raise this because there's still discussion over what sys.lazy_modules should be. The documentation for sys.lazy_modules currently states:

When a lazily imported module is accessed for the first time, its name is removed from this set.

In at least two cases I'm aware of names are not being removed. Names may also not be modules, but I'd consider that a documentation issue while I believe the failure to remove names is a bug.

Names of modules that have previously been resolved will be re-added, but not removed when resolved again.

import sys
mods = sys.lazy_modules.copy()
def get_lazy():
    return sorted(sys.lazy_modules - mods)

lazy import x  # added
print(get_lazy())
x  # removed
print(get_lazy())
lazy import x  # added again
x  # not removed
print(get_lazy())

['x']
[]
['x']

Here I think the issue is adding x back to sys.lazy_modules when it's already in sys.modules.

Names that are not modules are not removed:

import sys
mods = sys.lazy_modules.copy()
def get_lazy():
    return sorted(sys.lazy_modules - mods)

lazy from x import X
print(get_lazy())
X
print(get_lazy())  # Should be empty

['x', 'x.X']
['x.X']

CPython versions tested on:

3.15, CPython main branch

Operating systems tested on:

No response

Linked PRs

• gh-157714