Python 3.7 changes the pyc format by adding a flags byte. Even though it
is not necessary for us to match it, it is nice to be able to read pyc
files we emit for debugging the rewriter.
Update our custom pyc files to use that format. We write flags==0
meaning we still use the mtime+size format rather the newer hash format.
This makes mypy raise an error whenever it detects code which is
statically unreachable, e.g.
x: int
if isinstance(x, str):
... # Statement is unreachable [unreachable]
This is really neat and finds quite a few logic and typing bugs.
Sometimes the code is intentionally unreachable in terms of types, e.g.
raising TypeError when a function is given an argument with a wrong
type. In these cases a `type: ignore[unreachable]` is needed, but I
think it's a nice code hint.
The tests came via c629f6b18 and c61ff31ffa.
The fixes from there are kind of obsoleted by 4cd08f9 (moving to importlib),
but it makes sense to keep them as integration tests in general.
The `_pytest._code._reprcompare` that was referred to previously doesn't
exist -- it was moved to other places but wasn't updated. This regressed
in f423ce9c01. Now we don't want it
anymore, so keep the status quo by explicitly removing them.
ExitCode is used in several internal modules and hooks and so with type
annotations added, needs to be imported a lot.
_pytest.main, being the entry point, generally sits at the top of the
import tree.
So, it's not great to have ExitCode defined in _pytest.main, because it
will cause a lot of import cycles once type annotations are added (in
fact there is already one, which this change removes).
Move it to _pytest.config instead.
_pytest.main still imports ExitCode, so importing from there still
works, although external users should really be importing from `pytest`.
The convention is "assert result is expected". Pytest's error diffs now
reflect this. "-" means that sth. expected is missing in the result and
"+" means that there are unexpected extras in the result.
Fixes: #3333
Previously it would say:
> assert '123456789012...901234567890A' == '1234567890123...901234567890B'"
This makes it look like the "3" might be different already.
This is clearer, and it is OK to have potentially one less char in the
right one:
> assert '123456789012...901234567890A' == '123456789012...901234567890B'"
