WIP: Set permissions for atomic open_file()

CHANGES.rst

@@ -13,12 +13,15 @@ Unreleased
 - Remove unused compat shim for ``bytes``. (`#1195`_)
 - Expand unit testing around termui, especially getchar (Windows). (`#1116`_)
 -   Fix output on Windows Python 2.7 built with MSVC 14. #1342
+- ``open_file`` with ``atomic=True`` retains permissions of existing files and
+  respects the current umask for new files. (`#1376`_)
 
 .. _#1167: https://github.com/pallets/click/pull/1167
 .. _#1151: https://github.com/pallets/click/pull/1151
 .. _#1185: https://github.com/pallets/click/issues/1185
 .. _#1195: https://github.com/pallets/click/pull/1195
 .. _#1116: https://github.com/pallets/click/issues/1116
+.. _#1376: https://github.com/pallets/click/issues/1376
 
 Version 7.0
 -----------

click/_compat.py

@@ -1,6 +1,7 @@
 import re
 import io
 import os
+import stat
 import sys
 import codecs
 from weakref import WeakKeyDictionary
@@ -33,6 +34,12 @@ def _make_text_stream(stream, encoding, errors,
                                     force_readable=force_readable,
                                     force_writable=force_writable)
 
+def _get_current_umask():
+    """Get current umask."""
+    umask = os.umask(0)
+    os.umask(umask)
+    return umask
+
 
 def is_ascii_encoding(encoding):
     """Checks if a given encoding is ascii."""
@@ -512,7 +519,19 @@ def open_stream(filename, mode='r', encoding=None, errors='strict',
     else:
         f = os.fdopen(fd, mode)
 
-    return _AtomicFile(f, tmp_filename, os.path.realpath(filename)), True
+    real_filename = os.path.realpath(filename)
+
+    # Get permissions to set on the target file. If the target file already
+    # exists, retain its current permissions. If the target file will be
+    # created, respect the permissions from the current umask.
+    permissions = None
+    if not WIN:
+        try:
+            permissions = stat.S_IMODE(os.stat(real_filename).st_mode)
+        except OSError:
+            permissions = 0o666 & ~_get_current_umask()
+
+    return _AtomicFile(f, tmp_filename, real_filename, permissions), True
 
 
 # Used in a destructor call, needs extra protection from interpreter cleanup.
@@ -526,10 +545,11 @@ def open_stream(filename, mode='r', encoding=None, errors='strict',
 
 class _AtomicFile(object):
 
-    def __init__(self, f, tmp_filename, real_filename):
+    def __init__(self, f, tmp_filename, real_filename, permissions):
         self._f = f
         self._tmp_filename = tmp_filename
         self._real_filename = real_filename
+        self._permissions = permissions
         self.closed = False
 
     @property
@@ -546,6 +566,8 @@ def close(self, delete=False):
             except OSError:
                 pass
         _replace(self._tmp_filename, self._real_filename)
+        if self._permissions is not None:
+            os.chmod(self._real_filename, self._permissions)
         self.closed = True
 
     def __getattr__(self, name):

tests/test_utils.py

@@ -1,12 +1,13 @@
 import os
+import stat
 import sys
 
 import pytest
 
 import click
 import click.utils
 import click._termui_impl
-from click._compat import WIN, PY2
+from click._compat import WIN, PY2, _get_current_umask
 
 
 def test_echo(runner):
@@ -285,6 +286,43 @@ def cli(filename):
         assert result.output == 'foobar\nmeep\n'
 
 
+@pytest.mark.skipif(WIN, reason='os.chmod() is not fully supported on Windows.')
+@pytest.mark.parametrize('permissions', [
+    0o400,
+    0o444,
+    0o600,
+    0o644,
+ ])
+def test_open_file_atomic_permissions_existing_file(runner, permissions):
+    with runner.isolated_filesystem():
+        with open('existing.txt', 'w') as f:
+            f.write('content')
+        os.chmod('existing.txt', permissions)
+
+        @click.command()
+        @click.argument('filename')
+        def cli(filename):
+           click.open_file(filename, 'w', atomic=True).close()
+
+        result = runner.invoke(cli, ['existing.txt'])
+        assert result.exception is None
+        assert stat.S_IMODE(os.stat('existing.txt').st_mode) == permissions
+
+
+@pytest.mark.skipif(WIN, reason='os.chmod() is not fully supported on Windows.')
+def test_open_file_atomic_permissions_new_file(runner):
+    with runner.isolated_filesystem():
+        @click.command()
+        @click.argument('filename')
+        def cli(filename):
+            click.open_file(filename, 'w', atomic=True).close()
+
+        umask = _get_current_umask()
+        result = runner.invoke(cli, ['new.txt'])
+        assert result.exception is None
+        assert stat.S_IMODE(os.stat('new.txt').st_mode) == (0o666 & ~umask)
+
+
 @pytest.mark.xfail(WIN and not PY2, reason='God knows ...')
 def test_iter_keepopenfile(tmpdir):
     expected = list(map(str, range(10)))