# HG changeset patch
# User Franz Glasner <f.glasner@feldmann-mg.com>
# Date 1457518760 -3600
# Node ID 58af59d5af404f75d1cd78bbd5e33781d326e239
# Parent  6835a5663008d3f8950a7cdeb9c227acdd1ce2e2
A "safe_merge" that makes (shallow) copies instead of directly manipulating given containers

diff -r 6835a5663008 -r 58af59d5af40 configmix/__init__.py
--- a/configmix/__init__.py	Wed Mar 09 11:09:33 2016 +0100
+++ b/configmix/__init__.py	Wed Mar 09 11:19:20 2016 +0100
@@ -6,11 +6,6 @@
            See LICENSE for details.
 
 """
-#
-# NOTE: ONLY STANDARDLIB-IMPORTS IN THIS MODULE.
-#       ITS JUST FOR BOOTSTRAPPING WITH PYTHON2 and PYTHON3.
-#       NO `future`, `six`, ...
-#
 
 from __future__ import division, print_function, absolute_import
 
@@ -18,6 +13,9 @@
 __version__ = "0.0.dev0"
 
 
+import copy
+
+
 __all__ = []
 
 
@@ -54,3 +52,18 @@
             else:
                 user[k] = merge(user[k], v)
     return user
+
+
+def safe_merge(user, default):
+    """A more safe version of `merge()` that makes shallow copies of
+    the container objects.
+
+    """
+    user = copy.copy(user)
+    if isinstance(user, dict) and isinstance(default, dict):
+        for k, v in default.items():
+            if k not in user:
+                user[k] = copy.copy(v)
+            else:
+                user[k] = merge(user[k], v)
+    return user