flake8 動作確認

## 動作確認

### 通常実行

```python:src/sample.py
import os

class Sample:
    def __init__(self, x):
        self.x = x
```

```
# flake8 src
src/sample.py:1:1: F401 'os' imported but unused
src/sample.py:3:1: E302 expected 2 blank lines, found 1
```

```
# flake8 --show-source src
src/sample.py:1:1: F401 'os' imported but unused
import os
^
src/sample.py:3:1: E302 expected 2 blank lines, found 1
class Sample:
^
```

### Configファイルを指定した実行

```tox.ini
[flake8]
ignore = F401
```

```python:src/sample.py
import os

class Sample:
    def __init__(self, x):
        self.x = x
```

```
# flake8 --config=tox.ini src
src/sample.py:3:1: E302 expected 2 blank lines, found 1
```


#### max-line-length

```tox.ini
[flake8]
max-line-length = 59
```

```python:src/sample.py
class Sample:
    def __init__(self, x):
        self.x = x
        self.y = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
```

```
# flake8 --config=tox.ini src
src/sample.py:4:60: E501 line too long (60 > 59 characters)
```

#### max-line-length + ignore E501

```tox.ini
[flake8]
ignore = E501
max-line-length = 59
```

```python:src/sample.py
class Sample:
    def __init__(self, x):
        self.x = x
        self.y = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
```

```
# flake8 --config=tox.ini src

```

### ライブラリはインストールされている必要はない

```
# pip freeze
flake8==3.8.3
mccabe==0.6.1
mypy==0.782
mypy-extensions==0.4.3
pycodestyle==2.6.0
pyflakes==2.2.0
typed-ast==1.4.1
typing-extensions==3.7.4.3
```

```python:src/sample.py
import requests


class Sample:
    def fetch_json(self, url: str) -> dict:
        response = requests.get(url)
        return response.json()
```

```tox.ini
[flake8]
max-line-length = 59
```

```
# flake8 --config=tox.ini src

```



### ディレクトリごとに異なる設定にする



```python:src/sample.py
import requests


class Sample:
    def fetch_json(self, url: str) -> dict:
        response = requests.get(url)
        return response.json()
```

```python:src/tests/test_sample.py
from unittest import TestCase, main
from unittest.mock import MagicMock, call, patch

from src.sample import Sample


class TestSample(TestCase):
    def mocked_requests_get(*args, **kwargs):
        class MockResponse:
            def __init__(self, json_data, status_code):
                self.json_data = json_data
                self.status_code = status_code

            def json(self):
                return self.json_data

        if args[0] == 'http://example.com/test.json':
            return MockResponse({'key1': 'value1'}, 200)
        elif args[0] == 'http://example.com/another_test.json':
            return MockResponse({'key2': 'value2'}, 200)

        return MockResponse(None, 404)

    @patch('requests.get', side_effect=mocked_requests_get)
    def test_fetch_json(self, mock_get: MagicMock):
        sample = Sample()

        json_data = sample.fetch_json('http://example.com/test.json')
        self.assertEqual(json_data, {'key1': 'value1'})
        json_data = sample.fetch_json('http://example.com/another_test.json')
        self.assertEqual(json_data, {'key2': 'value2'})
        json_data = sample.fetch_json('http://no_example.com/test.json')
        self.assertIsNone(json_data)

        self.assertIn(
            call('http://example.com/test.json'), mock_get.call_args_list
        )
        self.assertIn(
            call('http://example.com/another_test.json'), mock_get.call_args_list
        )

        self.assertEqual(len(mock_get.call_args_list), 3)


if __name__ == '__main__':
    main()
```

```tox.ini
[flake8]
max-line-length = 79
```

```
# flake8 --config=tox.ini src
src/tests/test_sample.py:6:1: E302 expected 2 blank lines, found 1
src/tests/test_sample.py:38:80: E501 line too long (81 > 79 characters)
```

```tox.ini
[flake8]
max-line-length = 79
per-file-ignores =
    src/tests/*:E302,E501
```

```
# flake8 --config=tox.ini src

```

### クラス外部から非パブリックメソッドにアクセスしていないことを確認する

```python:src/sample.py
import requests


class Sample:
    def fetch_json(self, url: str) -> dict:
        response = self._get_response(url)
        return response.json()

    def _get_response(self, url: str) -> requests.models.Response:
        return requests.get(url)
```

調べた限りだとできない

## 参考

https://flake8.pycqa.org/en/latest/index.html