From 7c310e12efd97d7ae48eb1c196092bbe0c57842d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Sybren=20A=2E=20St=C3=BCvel?= <sybren@stuvel.eu>
Date: Wed, 12 Oct 2016 16:01:30 +0200
Subject: [PATCH] Added util function to compute the difference between two
 dicts.

---
 pillar/api/utils/__init__.py | 34 ++++++++++++++++++++++
 tests/test_api/test_utils.py | 56 ++++++++++++++++++++++++++++++++++++
 2 files changed, 90 insertions(+)

diff --git a/pillar/api/utils/__init__.py b/pillar/api/utils/__init__.py
index db9307ce..00f64696 100644
--- a/pillar/api/utils/__init__.py
+++ b/pillar/api/utils/__init__.py
@@ -113,3 +113,37 @@ def gravatar(email, size=64):
     return "https://www.gravatar.com/avatar/" + \
            hashlib.md5(str(email)).hexdigest() + \
            "?" + urllib.urlencode(parameters)
+
+
+class DoesNotExist(object):
+    """Returned as value by doc_diff if a value does not exist."""
+
+
+def doc_diff(doc1, doc2):
+    """Generator, yields differences between documents.
+
+    Yields changes as (key, value in doc1, value in doc2) tuples, where
+    the value can also be the DoesNotExist class. Does not report changed
+    private keys (i.e. starting with underscores).
+
+    Sub-documents (i.e. dicts) are recursed, and dot notation is used
+    for the keys if changes are found.
+    """
+
+    for key in set(doc1.keys()).union(set(doc2.keys())):
+        if isinstance(key, basestring) and key[0] == u'_':
+            continue
+
+        val1 = doc1.get(key, DoesNotExist)
+        val2 = doc2.get(key, DoesNotExist)
+
+        # Only recurse if both values are dicts
+        if isinstance(val1, dict) and isinstance(val2, dict):
+            for subkey, subval1, subval2 in doc_diff(val1, val2):
+                yield '%s.%s' % (key, subkey), subval1, subval2
+            continue
+
+        if val1 == val2:
+            continue
+
+        yield key, val1, val2
diff --git a/tests/test_api/test_utils.py b/tests/test_api/test_utils.py
index f7540a7c..f4dc4f65 100644
--- a/tests/test_api/test_utils.py
+++ b/tests/test_api/test_utils.py
@@ -1,4 +1,6 @@
 # -*- encoding: utf-8 -*-
+from __future__ import absolute_import
+import unittest
 
 from bson import ObjectId
 from pillar.tests import AbstractPillarTest
@@ -28,3 +30,57 @@ class Str2idTest(AbstractPillarTest):
         unhappy('')
         unhappy(u'')
         unhappy(None)
+
+
+class DocDiffTest(unittest.TestCase):
+    def test_no_diff_simple(self):
+        from pillar.api.utils import doc_diff
+        diff = doc_diff({'a': 'b', 3: 42},
+                        {'a': 'b', 3: 42})
+
+        self.assertEqual([], list(diff))
+
+    def test_no_diff_privates(self):
+        from pillar.api.utils import doc_diff
+        diff = doc_diff({'a': 'b', 3: 42, '_updated': 5133},
+                        {'a': 'b', 3: 42, '_updated': 42})
+
+        self.assertEqual([], list(diff))
+
+    def test_diff_values_simple(self):
+        from pillar.api.utils import doc_diff
+        diff = doc_diff({'a': 'b', 3: 42},
+                        {'a': 'b', 3: 513})
+
+        self.assertEqual([(3, 42, 513)], list(diff))
+
+    def test_diff_keys_simple(self):
+        from pillar.api.utils import doc_diff, DoesNotExist
+        diff = doc_diff({'a': 'b', 3: 42},
+                        {'a': 'b', 2: 42})
+
+        self.assertEqual({(3, 42, DoesNotExist), (2, DoesNotExist, 42)}, set(diff))
+
+    def test_no_diff_nested(self):
+        from pillar.api.utils import doc_diff
+        diff = doc_diff({'a': 'b', 'props': {'status': u'todo', 'notes': u'jemoeder'}},
+                        {'a': 'b', 'props': {'status': u'todo', 'notes': u'jemoeder'}})
+
+        self.assertEqual([], list(diff))
+
+    def test_diff_values_nested(self):
+        from pillar.api.utils import doc_diff
+        diff = doc_diff({'a': 'b', 'props': {'status': u'todo', 'notes': u'jemoeder'}},
+                        {'a': 'c', 'props': {'status': u'done', 'notes': u'jemoeder'}})
+
+        self.assertEqual({('a', 'b', 'c'), ('props.status', u'todo', u'done')},
+                         set(diff))
+
+    def test_diff_keys_nested(self):
+        from pillar.api.utils import doc_diff, DoesNotExist
+        diff = doc_diff({'a': 'b', 'props': {'status1': u'todo', 'notes': u'jemoeder'}},
+                        {'a': 'b', 'props': {'status2': u'todo', 'notes': u'jemoeder'}})
+
+        self.assertEqual({('props.status1', u'todo', DoesNotExist),
+                          ('props.status2', DoesNotExist, u'todo')},
+                         set(diff))