Inconsistent exclude behaviour

[asottile]

In GitLab by @mskrajnowski on Dec 13, 2017, 05:53

Please describe how you installed Flake8

# in a virtualenv
$ pip install flake8

Please provide the exact, unmodified output of flake8 --bug-report

{
  "dependencies": [
    {
      "dependency": "setuptools",
      "version": "34.2.0"
    }
  ],
  "platform": {
    "python_implementation": "CPython",
    "python_version": "2.7.12",
    "system": "Linux"
  },
  "plugins": [
    {
      "is_local": false,
      "plugin": "mccabe",
      "version": "0.6.1"
    },
    {
      "is_local": false,
      "plugin": "pycodestyle",
      "version": "2.3.1"
    },
    {
      "is_local": false,
      "plugin": "pyflakes",
      "version": "1.6.0"
    },
    {
      "is_local": false,
      "plugin": "unicode-string-literal",
      "version": "1.1"
    }
  ],
  "version": "3.5.0"
}

Please describe the problem or feature

Explicitly specified modules are not always checked, depending on what exclude is set:

• if the module is within an excluded directory it will be checked
• if the module filename is excluded it will not be checked

I would expect flake8 to either:

• always check files that are explicitly specified
• always ignore files that are excluded and/or in an excluded directory

If this is a bug report, please explain with examples (and example code) what you expected to happen and what actually happened.

1. Prepare a simple project for testing

   $ mkdir -p test-flake8-exclude/test
   $ cd test-flake8-exclude
   $ echo "import os" > test/module.py

2. Try without exclude

   $ flake8 . && echo OK
   ./test/module.py:1:1: F401 'os' imported but unused
   $ flake8 test/module.py && echo OK
   test/module.py:1:1: F401 'os' imported but unused

3. Try excluding the directory

   $ echo "[flake8]" > .flake8
   $ echo "exclude = test" >> .flake8
   
   $ flake8 . && echo OK
   OK
   $ flake8 test/module.py && echo OK
   test/module.py:1:1: F401 'os' imported but unused

4. Try excluding the module

   $ echo "[flake8]" > .flake8
   $ echo "exclude = module.py" >> .flake8
   
   $ flake8 . && echo OK
   OK
   $ flake8 test/module.py && echo OK
   OK

I'd expect results in 3. and 4. to be the same.