It's better to have the documentation in one place, instead
of having some in the docstring and some additional
information added to the reference documentation in
`reference.rst`.
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Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Anthony Sottile <asottile@umich.edu>
In order to allow users to type annotate fixtures they request, the
types need to be imported from the `pytest` namespace. They are/were
always available to import from the `_pytest` namespace, but that is
not guaranteed to be stable.
These types are only exported for the purpose of typing. Specifically,
the following are *not* public:
- Construction (`__init__`)
- Subclassing
- staticmethods and classmethods
We try to combat them being used anyway by:
- Marking the classes as `@final` when possible (already done).
- Not documenting private stuff in the API Reference.
- Using `_`-prefixed names or marking as `:meta private:` for private
stuff.
- Adding a keyword-only `_ispytest=False` to private constructors,
warning if False, and changing pytest itself to pass True. In the
future it will (hopefully) become a hard error.
Hopefully that will be enough.
Don't import `pytest` from within some `_pytest` modules since an
upcoming commit will import from them into `pytest`.
It would have been nice not to have to do it, so that internal plugins
look more like external plugins, but with the existing layout this seems
unavoidable.
This indicates at least for people using type checkers that these
classes are not designed for inheritance and we make no stability
guarantees regarding inheritance of them.
Currently this doesn't show up in the docs. Sphinx does actually support
`@final`, however it only works when imported directly from `typing`,
while we import from `_pytest.compat`.
In the future there might also be a `@sealed` decorator which would
cover some more cases.
The `CaptureManager.global_and_fixture_disabled()` context manager (and
`CaptureFixture.disabled()` which calls it) did `suspend(); ...;
resume()` but if the capturing was already suspended, the `resume()`
would resume it when it shouldn't.
This caused caused some messages to be swallowed when `--log-cli` is
used because it uses `global_and_fixture_disabled` when capturing is not
necessarily resumed.
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.
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.
There are state transitions start/done/suspend/resume and two additional
operations snap/writeorg.
Previously it was not well defined in what order they can be called, and
which operations are idempotent.
Formalize this and enforce using assert checks with informative error
messages if they fail (rather than random AttributeErrors).
Make it easier to read the file in progression, and avoid forward
references for upcoming type annotations.
There is one cycle, CaptureManager <-> CaptureFixture, which is hard to
untangle.
(This commit should be added to `.gitblameignore`).
The `FDCapture`/`FDCaptureBinary` classes, used by `capfd`/`capfdbinary`
fixtures and the `--capture=fd` option (set by default), redirect FDs
1/2 (stdout/stderr) to a temporary file. To do this, they need to save
the old file by duplicating the FD before redirecting it, to be restored
once finished.
Previously, if this duplicating (`os.dup()`) failed, most likely due to
that FD being invalid, the FD redirection would silently not be done. The
FD capturing also performs python-level redirection (monkeypatching
`sys.stdout`/`sys.stderr`) which would still be done, but direct writes
to the FDs would fail.
This is not great. If pytest is run with `--capture=fd`, or a test is
using `capfd`, it expects writes to the FD to work and be captured,
regardless of external circumstances.
So, instead of disabling FD capturing, keep the redirection to a
temporary file, just don't restore it after closing, because there is
nothing to restore to.
Move {Passthrough,CaptureIO} to capture module, and rename Passthrough
-> Tee to match the existing terminology.
Co-authored-by: Ran Benita <ran@unusedvar.com>
Previously, writing to sys.stdout/stderr in text-mode (e.g.
`print('foo')`) while a `capsysbinary` fixture is active, would crash
with:
/usr/lib/python3.7/contextlib.py:119: in __exit__
next(self.gen)
E TypeError: write() argument must be str, not bytes
This is due to some confusion in the types. The relevant functions are
`snap()` and `writeorg()`. The function `snap()` returns what was
captured, and the return type should be `bytes` for the binary captures
and `str` for the regular ones. The `snap()` return value is eventually
passed to `writeorg()` to be written to the original file, so it's input
type should correspond to `snap()`. But this was incorrect for
`SysCaptureBinary`, which handled it like `str`.
To fix this, be explicit in the `snap()` and `writeorg()`
implementations, also of the other Capture types.
We can't add type annotations yet, because the current inheritance
scheme breaks Liskov Substitution and mypy would complain. To be
refactored later.
Fixes: https://github.com/pytest-dev/pytest/issues/6871
Co-authored-by: Ran Benita (some modifications & commit message)
I tried to understand what the `safe_text_dupfile()` function and
`EncodedFile` class do. Outside tests, `EncodedFile` is only used by
`safe_text_dupfile`, and `safe_text_dupfile` is only used by
`FDCaptureBinary.__init__()`. I then started to eliminate always-true
conditions based on the single call site, and in the end nothing was
left except of a couple workarounds that are still needed.
The commit which added the checks for os.dup a15afb5e48
suggests it was done for Jython. But pytest doesn't support Jython
anymore (Jython is Python 2 only).
Furthermore, it looks like the faulthandler plugin (bundled in pytest
and enabled by default) uses os.dup() unprotected and there have not
been any complaints.
So seems better to just remove these checks, and only add if someone
with a legitimate use case complains.
