Error when using floats in pyproject.toml

[siehar]

Steps to reproduce

Add a pyproject.toml to the project with this content:

[tool.pylint.master]
fail-under = 9.4

When running pylint, it aborts with an exception.

Full traceback:

Traceback (most recent call last):
  File "/test/virtualenv/bin/pylint", line 8, in <module>
    sys.exit(run_pylint())
  File "/test/virtualenv/lib/python3.8/site-packages/pylint/__init__.py", line 24, in run_pylint
    PylintRun(sys.argv[1:])
  File "/test/virtualenv/lib/python3.8/site-packages/pylint/lint/run.py", line 333, in __init__
    linter.load_config_file()
  File "/test/virtualenv/lib/python3.8/site-packages/pylint/config/option_manager_mixin.py", line 313, in load_config_file
    for option, value in parser.items(section):
  File "/usr/lib/python3.8/configparser.py", line 859, in items
    return [(option, value_getter(option)) for option in orig_keys]
  File "/usr/lib/python3.8/configparser.py", line 859, in <listcomp>
    return [(option, value_getter(option)) for option in orig_keys]
  File "/usr/lib/python3.8/configparser.py", line 855, in <lambda>
    value_getter = lambda option: self._interpolation.before_get(self,
  File "/usr/lib/python3.8/configparser.py", line 395, in before_get
    self._interpolate_some(parser, option, L, value, section, defaults, 1)
  File "/usr/lib/python3.8/configparser.py", line 412, in _interpolate_some
    p = rest.find("%")
AttributeError: 'float' object has no attribute 'find'

Current behavior

With fail-under = 9 the behaviour is as expected, using a floating point value leads to an exception.

Expected behavior

Floating point values should work.

pylint --version output

Result of pylint --version output:

pylint --version
pylint 3.0.0a3
astroid 2.5.6
Python 3.8.5 (default, Jan 27 2021, 15:41:15) 
[GCC 9.3.0]

But also tested with latest release version 2.8.2 and it also happens there.

Reason

The issue seems to come from here: https://github.com/PyCQA/pylint/blob/master/pylint/config/option_manager_mixin.py#L281

Floats coming from the TOML parser aren't handled here which later on confuses ConfigParser.

A simple fix would be to change isinstance(value, int) to isinstance(value, (int, float)).

I tried that fix and it works though I'm not sure if there are some weird edge cases where this breaks.

[Pierre-Sassoulas]

Thank you for the report and the analysis. Would you mind making a pull request for it as you already did most of the work ? (I don't think there will be edge cases :) )