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
@@ -503,16 +504,34 @@ def open_stream(filename, mode='r', encoding=None, errors='strict',
     # as a proxy in the same folder and then using the fdopen
     # functionality to wrap it in a Python file.  Then we wrap it in an
     # atomic file that moves the file over on close.
-    import tempfile
-    fd, tmp_filename = tempfile.mkstemp(dir=os.path.dirname(filename),
-                                        prefix='.__atomic-write')
+    #
+    # The vendored tempfile modules are modified to respect the current umask when
+    # creating the file.
+    if PY2:
+        from . import _tempfile27 as _tempfile
+    else:
+        from . import _tempfile36 as _tempfile
+    fd, tmp_filename = _tempfile.mkstemp(dir=os.path.dirname(filename),
+                                         prefix='.__atomic-write')
 
     if encoding is not None:
         f = io.open(fd, mode, encoding=encoding, errors=errors)
     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, IOError):
+            pass
+
+    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):