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.
This option checks even functions which are not annotated. It's a good
step to ensure that existing type annotation are correct.
In a Pareto fashion, the last few holdouts are always the ugliest,
beware.
This makes a difference for e.g. pytest-xdist:
Before:
```
--dist=distmode set mode for distributing tests to exec environments. each: …
available environment. loadscope: …
grouped by file to any available environment. (default) no: …
```
After:
```
--dist=distmode set mode for distributing tests to exec environments.
each: send each test to all available environments.
load: load balance by sending any pending test to any available environment.
…
(default) no: run tests inprocess, don't distribute.
```
This might also result in unexpected changes (hard wrapping), when line
endings where used unintentionally, e.g. with:
```
help="""
some long
help text
"""
```
But the benefits from that are worth it, and it is easy to fix, as will
be done for the internal `assertmode` option.
The default message is often hard to read:
E _pytest.config.ConftestImportFailure: (local('D:\\projects\\pytest\\.tmp\\root\\foo\\conftest.py'), (<class 'RuntimeError'>, RuntimeError('some error',), <traceback object at 0x000001CCC3E39348>))
Using a shorter message is better:
E _pytest.config.ConftestImportFailure: RuntimeError: some error (from D:\projects\pytest\.tmp\root\foo\conftest.py)
And we don't really lose any information due to exception chaining.
This removes the KeyError from the traceback chain when an
conftest fails to import:
return self._conftestpath2mod[key]
E KeyError: WindowsPath('D:/projects/pytest/.tmp/root/foo/conftest.py')
During handling of the above exception, another exception occurred:
...
raise RuntimeError("some error")
E RuntimeError: some error
During handling of the above exception, another exception occurred:
...
E _pytest.config.ConftestImportFailure: (...)
By slightly changing the code, we can remove the first chain, which is often
very confusing to users and doesn't help with anything.
Fix#7223
