Enforce docparams consistently when docstring is not present

[kevinoid]

Currently pylint.extensions.docparams produces missing-return-doc, missing-return-type-doc, and missing-yield-doc, missing-yield-type-doc errors for functions without a docstring. This differs from missing-param-doc, missing-raises-doc, and missing-type-doc which are not produced for functions without a docstring.

Since pylint.extensions.docparams does not use the no-docstring-rgx or docstring-min-length options, producing these errors for missing docstrings is problematic. It provides no way to configure pylint to warn about missing return/yield documentation only when documentation is required (e.g. ignoring undocumented private methods) which seems like a valuable use case.

Steps to reproduce

1. Create .pylintrc with the following content:

[MASTER]
load-plugins = pylint.extensions.docparams

[BASIC]
accept-no-param-doc = no
accept-no-raise-doc = no
accept-no-return-doc = no
accept-no-yields-doc = no

2. Create fixture_docparams_missing.py with the following content:

"""Fixture for testing missing documentation in docparams."""

def _private_func(param1):
    if param1:
        raise Exception('Example')
    return param1

def _private_func2(param1):
    yield param1

3. Run pylint fixture_docparams_missing.py

Current behavior

************* Module fixture_docparams_missing
fixture_docparams_missing.py:3:0: W9011: Missing return documentation (missing-return-doc)
fixture_docparams_missing.py:3:0: W9012: Missing return type documentation (missing-return-type-doc)
fixture_docparams_missing.py:8:0: W9013: Missing yield documentation (missing-yield-doc)
fixture_docparams_missing.py:8:0: W9014: Missing yield type documentation (missing-yield-type-doc)

------------------------------------------------------------------
Your code has been rated at 3.33/10 (previous run: 3.33/10, +0.00)

Expected behavior

No errors (due to missing-docstring suppressed by default no-docstring-rgx).

Alternatively, all missing-* error types produced by pylint.extensions.docparams and a configuration option to suppress the errors in a similar way to no-docstring-rgx.

pylint --version output

From a local clone of 51e12f8:

__main__.py 2.3.0-dev1
astroid 2.1.0
Python 3.7.2+ (default, Feb  2 2019, 14:31:48) 
[GCC 8.2.0]

Thanks for considering,
Kevin

[PCManticore]

Hey @kevinoid I think this makes sense, thanks for raising the issue. @AWhetter let me know if you have a different opinion.

[AWhetter]

Makes sense to me too.
@PCManticore Is it possible to use the value of an option defined by another checker?

[PCManticore]

@AWhetter Yep, you can use pylint.utils.get_global_option for that, e.g. get_global_option(self, "option-name", default=default_value)