Merge pull request #75 from theevocater/jakeman/stdin

Add '-' to read from stdin

add_trailing_comma.py

 from __future__ import absolute_import
+from __future__ import print_function
 from __future__ import unicode_literals
 
 import argparse
@@ -405,24 +406,29 @@ def _fix_src(contents_text, py35_plus, py36_plus):
 
 
 def fix_file(filename, args):
-    with open(filename, 'rb') as f:
-        contents_bytes = f.read()
+    if filename == '-':
+        contents_bytes = getattr(sys.stdin, 'buffer', sys.stdin).read()
+    else:
+        with open(filename, 'rb') as f:
+            contents_bytes = f.read()
 
     try:
         contents_text_orig = contents_text = contents_bytes.decode('UTF-8')
     except UnicodeDecodeError:
-        print('{} is non-utf-8 (not supported)'.format(filename))
+        msg = '{} is non-utf-8 (not supported)'.format(filename)
+        print(msg, file=sys.stderr)
         return 1
 
     contents_text = _fix_src(contents_text, args.py35_plus, args.py36_plus)
 
-    if contents_text != contents_text_orig:
-        print('Rewriting {}'.format(filename))
+    if filename == '-':
+        print(contents_text, end='')
+    elif contents_text != contents_text_orig:
+        print('Rewriting {}'.format(filename), file=sys.stderr)
         with io.open(filename, 'w', newline='', encoding='UTF-8') as f:
             f.write(contents_text)
-        return 1
 
-    return 0
+    return contents_text != contents_text_orig
 
 
 def main(argv=None):

requirements-dev.txt

 coverage
 flake8
+mock
 pre-commit
 pytest

tests/add_trailing_comma_test.py

@@ -3,8 +3,10 @@ from __future__ import absolute_import
 from __future__ import unicode_literals
 
 import ast
+import io
 import sys
 
+import mock
 import pytest
 
 from add_trailing_comma import _fix_src
@@ -846,8 +848,8 @@ def test_main_changes_a_file(tmpdir, capsys):
     f = tmpdir.join('f.py')
     f.write('x(\n    1\n)\n')
     assert main((f.strpath,)) == 1
-    out, _ = capsys.readouterr()
-    assert out == 'Rewriting {}\n'.format(f.strpath)
+    _, err = capsys.readouterr()
+    assert err == 'Rewriting {}\n'.format(f.strpath)
     assert f.read() == 'x(\n    1,\n)\n'
 
 
@@ -855,8 +857,8 @@ def test_main_preserves_line_endings(tmpdir, capsys):
     f = tmpdir.join('f.py')
     f.write_binary(b'x(\r\n    1\r\n)\r\n')
     assert main((f.strpath,)) == 1
-    out, _ = capsys.readouterr()
-    assert out == 'Rewriting {}\n'.format(f.strpath)
+    _, err = capsys.readouterr()
+    assert err == 'Rewriting {}\n'.format(f.strpath)
     assert f.read_binary() == b'x(\r\n    1,\r\n)\r\n'
 
 
@@ -870,8 +872,8 @@ def test_main_non_utf8_bytes(tmpdir, capsys):
     f = tmpdir.join('f.py')
     f.write_binary('# -*- coding: cp1252 -*-\nx = €\n'.encode('cp1252'))
     assert main((f.strpath,)) == 1
-    out, _ = capsys.readouterr()
-    assert out == '{} is non-utf-8 (not supported)\n'.format(f.strpath)
+    _, err = capsys.readouterr()
+    assert err == '{} is non-utf-8 (not supported)\n'.format(f.strpath)
 
 
 def test_main_py35_plus_argument_star_args(tmpdir):
@@ -911,3 +913,19 @@ def test_main_py36_plus_function_trailing_commas(
     assert f.read() == 'def f(\n    **kwargs\n): pass\n'
     assert main((f.strpath, '--py36-plus')) == 1
     assert f.read() == 'def f(\n    **kwargs,\n): pass\n'
+
+
+def test_main_stdin_no_changes(capsys):
+    stdin = io.TextIOWrapper(io.BytesIO(b'x = 5\n'), 'UTF-8')
+    with mock.patch.object(sys, 'stdin', stdin):
+        assert main(('-',)) == 0
+    out, err = capsys.readouterr()
+    assert out == 'x = 5\n'
+
+
+def test_main_stdin_with_changes(capsys):
+    stdin = io.TextIOWrapper(io.BytesIO(b'x(\n    1\n)\n'), 'UTF-8')
+    with mock.patch.object(sys, 'stdin', stdin):
+        assert main(('-',)) == 1
+    out, err = capsys.readouterr()
+    assert out == 'x(\n    1,\n)\n'