In Python, if module A defines a name `name`, and module B does `import
name from A`, then another module C can `import name from B`.
Sometimes it is intentional -- module B is meant to "reexport" `name`.
But sometimes it is just confusion/inconsistency on where `name` should
be imported from.
mypy has a flag `--no-implicit-reexport` which puts some order into
this. A name can only be imported from a module if
1. The module defines the name
2. The module's `__all__` includes the name
3. The module imports the name as `from ... import .. as name`.
This flag is included in mypy's `--strict` flag.
I like this flag, but I realize it is a bit controversial, and in
particular item 3 above is a bit unfriendly to contributors who don't
know about it. So I didn't intend to add it to pytest.
But while investigating issue 7589 I came upon mypy issue 8754 which
causes `--no-implicit-reexport` to leak into installed libraries and
causes some unexpected typing differences *in pytest* if the user uses
this flag.
Since the diff mostly makes sense, let's just conform to it.
Part of reducing dependency on `py`. Also enables upcoming improvements.
In cases where there are simpler alternatives (in tests), I used those.
What's left are a couple of uses in `_pytest.main` and `_pytest.python`
and they only have modest requirements, so all of the featureful code
from py is not needed.
This function is exposed and kept alive for the oejskit plugin which is
abandoned and no longer works with recent plugins, so let's prepare to
completely remove it.
The dynamic scope feature added in 10bf6aac76
necessitated some wrangling of arguments in pytest.fixture(). In
particular, it deprecated positional arguments in favor of keyword-only
arguments, while keeping backward compatibility.
The way it did this avoided some code duplication but ended up being
quite hard to follow and to annotate with types.
Replace it with some straightforward code, which is not very DRY but is
simple and easy to remove when the time comes.