Change deprecation mechanism to use a function

As discussed in #7362 (comment)_, let's change our warnings mechanism to include a new PytestExpiredDeprecationWarning exception which is chosen at runtime depending on the current pytest version.

This will simplify our side because we won't need to change PytestDeprecationWarnings into errors anymore before each major release.

Also, test_deprecation_warning_as_error will probably be removed.

I'll be reverting these entries from the CHANGELOG:

- `#6981 <https://github.com/pytest-dev/pytest/issues/6981>`_: Deprecate the ``pytest.collect`` module as it's just aliases into ``pytest``.


- `#7097 <https://github.com/pytest-dev/pytest/issues/7097>`_: The ``pytest._fillfuncargs`` function is now deprecated. This function was kept
  for backward compatibility with an older plugin.

  It's functionality is not meant to be used directly, but if you must replace
  it, use `function._request._fillfixtures()` instead, though note this is not
  a public API and may break in the future.

EDIT: done in #7482

@RonnyPfannschmidt

@RonnyPfannschmidt I just realized something.

The plan here is to have a function somewhat like this:

def deprecated(reason: str, *, due: int, stacklevel: int):
    if due >= pytest version [0]:
        warnings.warn(PytestExpiredDeprecationWarning(reason), stacklevel=stacklevel)
    else:
        warnings.warn(PytestDeprecationWarning(reason), stacklevel=stacklevel)

Usage:

def use_of_deprecated_thing():
   deprecated("don't use this function, use X instead", due=7)
   # do its thing

However, because our version depends on the tag of the release, the actual pytest version will stay 6.X until the actual tag 7.0.0 is pushed at release time, and in that moment that function will issue PytestExpiredDeprecationWarning, which will then break the actual release. Any ideas?

For implementation towncrier support in setuptools_scm is intended and planned

For implementation towncrier support in setuptools_scm is intended and planned

Not sure what you mean, can you elaborate please?

Remember the stacklevel for warnings.warn:

def deprecated(reason: str, *, due: int, stacklevel=0):
    stacklevel = stacklevel + 1
    if due >= pytest version [0]:
        warnings.warn(PytestExpiredDeprecationWarning(reason), stacklevel=stacklevel)
    else:
        warnings.warn(PytestDeprecationWarning(reason), stacklevel=stacklevel)

I strongly oppose combining declaration and triggering of warnings

@nicoddemus

@nicoddemus if the next guessed version is based on semver + towncrier inference, it's 7.0.dev... As soon as a breaking change is merged

@nicoddemus

I strongly oppose combining declaration and triggering of warnings

Noted, just to get this out of the way then:

def deprecated_warning(reason: str, *, due: int) -> PytestWarning:
    if due >= pytest version [0]:
        return PytestExpiredDeprecationWarning(reason)
    else:
        return PytestDeprecationWarning(reason)

@nicoddemus if the next guessed version is based on semver + towncrier inference, it's 7.0.dev... As soon as a breaking change is merged

Ahh I see, thanks.

Should we hold this issue until that happens then?

Yup

Ahh I found it: pypa/setuptools-scm#332

OK then, let's hold then.

This will simplify our side because we won't need to change PytestDeprecationWarnings into errors anymore before each major release.

Is this a major headache? Making things conditional on our own __version__ might cause some headaches of its own...

BTW, Django does something I like, which is embed the removal version in the warning type. This brings clarity to all involved, but might be getting too fancy.

Adapted to pytest (as of version 6.1), this would be:

# Existing class
class PytestDeprecationWarning(PytestWarning, DeprecationWarning): ...

# New class
class PytestExpiredDeprecationWarning(PytestWarning, DeprecationWarning): ...

# New class
class PytestPendingDeprecationWarning(PytestWarning, PendingDeprecationWarning): ...

class PytestRemovedInPytest7Warning(PytestDeprecationWarning): ...

class PytestRemovedInPytest8Warning(PytestPendingDeprecationWarning): ...

When pytest 7 is released, changes to

class PytestRemovedInPytest7Warning(PytestExpiredDeprecationWarning): ...

class PytestRemovedInPytest8Warning(PytestDeprecationWarning): ...

class PytestRemovedInPytest9Warning(PytestPendingDeprecationWarning): ...

When pytest 7.1 is released, changes to

class PytestRemovedInPytest8Warning(PytestDeprecationWarning): ...

class PytestRemovedInPytest9Warning(PytestPendingDeprecationWarning): ...

The PytestDeprecationWarning should be used when adding deprecations right before a major release (when we had this case in pytest 6.0, we disabled them until after the release instead).

based on experiences in pip and a few internal tools, the self version dependency seems orders of magnitude better than any manually managed way to deal with it

Categorize deprecation warnings to `PytestRemovedInXWarning`

chore(deps): update dependency pytest to v7 (#3)

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Change deprecation mechanism to use a function #7480

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Change deprecation mechanism to use a function #7480

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nicoddemus commented on Jul 11, 2020

nicoddemus commented on Jul 11, 2020

nicoddemus commented on Aug 21, 2020

RonnyPfannschmidt commented on Aug 21, 2020

nicoddemus commented on Aug 21, 2020

graingert commented on Aug 21, 2020

RonnyPfannschmidt commented on Aug 21, 2020

RonnyPfannschmidt commented on Aug 21, 2020

nicoddemus commented on Aug 21, 2020

RonnyPfannschmidt commented on Aug 21, 2020

nicoddemus commented on Aug 21, 2020

bluetech commented on Aug 22, 2020

RonnyPfannschmidt commented on Aug 22, 2020

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