Add encoding pragma hook. Resolves pre-commit/pre-commit#15

tests/fix_encoding_pragma_test.py

@@ -0,0 +1,82 @@
+from __future__ import absolute_import
+from __future__ import unicode_literals
+
+import io
+
+import pytest
+
+from pre_commit_hooks.fix_encoding_pragma import fix_encoding_pragma
+from pre_commit_hooks.fix_encoding_pragma import main
+
+
+def test_integration_inserting_pragma(tmpdir):
+    file_path = tmpdir.join('foo.py').strpath
+
+    with open(file_path, 'wb') as file_obj:
+        file_obj.write(b'import httplib\n')
+
+    assert main([file_path]) == 1
+
+    with open(file_path, 'rb') as file_obj:
+        assert file_obj.read() == (
+            b'# -*- coding: utf-8 -*-\n'
+            b'import httplib\n'
+        )
+
+
+def test_integration_ok(tmpdir):
+    file_path = tmpdir.join('foo.py').strpath
+    with open(file_path, 'wb') as file_obj:
+        file_obj.write(b'# -*- coding: utf-8 -*-\nx = 1\n')
+    assert main([file_path]) == 0
+
+
+@pytest.mark.parametrize(
+    'input_str',
+    (
+        b'',
+        b'# -*- coding: utf-8 -*-\n',
+        (
+            b'#!/usr/bin/env python\n'
+            b'# -*- coding: utf-8 -*-\n'
+            b'foo = "bar"\n'
+        ),
+    )
+)
+def test_ok_inputs(input_str):
+    bytesio = io.BytesIO(input_str)
+    assert fix_encoding_pragma(bytesio) == 0
+    bytesio.seek(0)
+    assert bytesio.read() == input_str
+
+
+@pytest.mark.parametrize(
+    ('input_str', 'output'),
+    (
+        (
+            b'import httplib\n',
+            b'# -*- coding: utf-8 -*-\n'
+            b'import httplib\n',
+        ),
+        (
+            b'#!/usr/bin/env python\n',
+            b'#!/usr/bin/env python\n'
+            b'# -*- coding: utf-8 -*-\n'
+        ),
+        (
+            b'#coding=utf-8\n',
+            b'# -*- coding: utf-8 -*-\n'
+        ),
+        (
+            b'#!/usr/bin/env python\n'
+            b'#coding=utf8\n',
+            b'#!/usr/bin/env python\n'
+            b'# -*- coding: utf-8 -*-\n',
+        ),
+    )
+)
+def test_not_ok_inputs(input_str, output):
+    bytesio = io.BytesIO(input_str)
+    assert fix_encoding_pragma(bytesio) == 1
+    bytesio.seek(0)
+    assert bytesio.read() == output