From 8065eddf41b9dc4d781c00fafd68c64eeed20412 Mon Sep 17 00:00:00 2001
From: Fabio Caccamo <fabio.caccamo@gmail.com>
Date: Thu, 17 Sep 2020 14:09:59 +0200
Subject: [PATCH] Added empty option to clone utility method.

---
 benedict/core/clone.py     |  7 +++++--
 benedict/core/filter.py    |  5 +++--
 benedict/core/flatten.py   |  4 ++--
 benedict/core/invert.py    |  4 ++--
 benedict/core/subset.py    |  4 ++--
 benedict/core/unflatten.py |  4 ++--
 tests/core/test_clone.py   | 12 ++++++++++++
 7 files changed, 28 insertions(+), 12 deletions(-)

diff --git a/benedict/core/clone.py b/benedict/core/clone.py
index d17ab62..04df72a 100644
--- a/benedict/core/clone.py
+++ b/benedict/core/clone.py
@@ -3,5 +3,8 @@
 import copy
 
 
-def clone(obj):
-    return copy.deepcopy(obj)
+def clone(obj, empty=False):
+    d = copy.deepcopy(obj)
+    if empty:
+        d.clear()
+    return d
diff --git a/benedict/core/filter.py b/benedict/core/filter.py
index f9e26fe..2563dd9 100644
--- a/benedict/core/filter.py
+++ b/benedict/core/filter.py
@@ -1,11 +1,12 @@
 # -*- coding: utf-8 -*-
 
+from benedict.core import clone
+
 
 def filter(d, predicate):
     if not callable(predicate):
         raise ValueError('predicate argument must be a callable.')
-    new_dict = d.copy()
-    new_dict.clear()
+    new_dict = clone(d, empty=True)
     keys = list(d.keys())
     for key in keys:
         value = d.get(key, None)
diff --git a/benedict/core/flatten.py b/benedict/core/flatten.py
index 4c3648e..680d14a 100644
--- a/benedict/core/flatten.py
+++ b/benedict/core/flatten.py
@@ -1,5 +1,6 @@
 # -*- coding: utf-8 -*-
 
+from benedict.core import clone
 from benedict.utils import type_util
 
 
@@ -10,8 +11,7 @@ def _flatten_key(base_key, key, separator):
 
 
 def flatten(d, separator='_', **kwargs):
-    new_dict = d.copy()
-    new_dict.clear()
+    new_dict = clone(d, empty=True)
     keys = list(d.keys())
     base_key = kwargs.pop('base_key', '')
     for key in keys:
diff --git a/benedict/core/invert.py b/benedict/core/invert.py
index a84ac4c..d3ab7f6 100644
--- a/benedict/core/invert.py
+++ b/benedict/core/invert.py
@@ -1,5 +1,6 @@
 # -*- coding: utf-8 -*-
 
+from benedict.core import clone
 from benedict.utils import type_util
 
 
@@ -16,8 +17,7 @@ def _invert_list(d, key, value, flat):
 
 
 def invert(d, flat=False):
-    new_dict = d.copy()
-    new_dict.clear()
+    new_dict = clone(d, empty=True)
     for key, value in d.items():
         if type_util.is_list_or_tuple(value):
             _invert_list(new_dict, key, value, flat)
diff --git a/benedict/core/subset.py b/benedict/core/subset.py
index 6c5a452..2d4e224 100644
--- a/benedict/core/subset.py
+++ b/benedict/core/subset.py
@@ -1,11 +1,11 @@
 # -*- coding: utf-8 -*-
 
+from benedict.core import clone
 from benedict.utils import type_util
 
 
 def subset(d, keys, *args):
-    new_dict = d.copy()
-    new_dict.clear()
+    new_dict = clone(d, empty=True)
     if type_util.is_string(keys):
         keys = [keys]
     keys += args
diff --git a/benedict/core/unflatten.py b/benedict/core/unflatten.py
index 40c142b..adcdce6 100644
--- a/benedict/core/unflatten.py
+++ b/benedict/core/unflatten.py
@@ -1,5 +1,6 @@
 # -*- coding: utf-8 -*-
 
+from benedict.core import clone
 from benedict.dicts.keylist import keylist_util
 from benedict.utils import type_util
 
@@ -12,8 +13,7 @@ def _unflatten_item(key, value, separator):
 
 
 def unflatten(d, separator='_'):
-    new_dict = d.copy()
-    new_dict.clear()
+    new_dict = clone(d, empty=True)
     keys = list(d.keys())
     for key in keys:
         value = d.get(key, None)
diff --git a/tests/core/test_clone.py b/tests/core/test_clone.py
index 5b15e73..d6598d7 100644
--- a/tests/core/test_clone.py
+++ b/tests/core/test_clone.py
@@ -22,3 +22,15 @@ class clone_test_case(unittest.TestCase):
         o['a']['b']['c'] = 2
         self.assertEqual(i['a']['b']['c'], 1)
         self.assertEqual(o['a']['b']['c'], 2)
+
+    def test_clone_empty(self):
+        i = {
+            'a': {
+                'b': {
+                    'c': 1
+                }
+            }
+        }
+        o = _clone(i, empty=True)
+        self.assertEqual(type(i), type(o))
+        self.assertEqual(o, {})