Merge pull request #22 from toumorokoshi/toum/append_unique_unhashable

make strategy_append_unique work for unhashables

Makefile

@@ -11,7 +11,7 @@ build: .venv/deps
 
 # only works with python 3+
 lint: .venv/deps
-	.venv/bin/python -m pip install black==21.12b0
+	.venv/bin/python -m pip install black==22.3.0
 	.venv/bin/python -m black --check .
 
 test: .venv/deps

deepmerge/extended_set.py

@@ -0,0 +1,25 @@
+class ExtendedSet(set):
+    """
+    ExtendedSet is an extension of set, which allows for usage
+    of types that are typically not allowed in a set
+    (e.g. unhashable).
+
+    The following types that cannot be used in a set are supported:
+
+    - unhashable types
+    """
+
+    def __init__(self, elements):
+        self._values_by_hash = {self._hash(e): e for e in elements}
+
+    def _insert(self, element):
+        self._values_by_hash[self._hash(element)] = element
+
+    def _hash(self, element):
+        if getattr(element, "__hash__") is not None:
+            return hash(element)
+        else:
+            return hash(str(element))
+
+    def __contains__(self, obj):
+        return self._hash(obj) in self._values_by_hash

deepmerge/strategy/list.py

@@ -1,4 +1,5 @@
 from .core import StrategyList
+from ..extended_set import ExtendedSet
 
 
 class ListStrategies(StrategyList):
@@ -26,5 +27,5 @@ def strategy_append(config, path, base, nxt):
     @staticmethod
     def strategy_append_unique(config, path, base, nxt):
         """append items without duplicates in nxt to base."""
-        base_as_set = set(base)
+        base_as_set = ExtendedSet(base)
         return base + [n for n in nxt if n not in base_as_set]

deepmerge/tests/strategy/test_list.py

@@ -19,3 +19,15 @@ def test_strategy_append_unique(custom_merger):
     expected = [1, 3, 2, 5, 4]
     actual = custom_merger.merge(base, nxt)
     assert actual == expected
+
+
+def test_strategy_append_unique_nested_dict(custom_merger):
+    """append_unique should work even with unhashable objects
+    Like dicts.
+    """
+    base = [{"bar": ["bob"]}]
+    nxt = [{"bar": ["baz"]}]
+
+    result = custom_merger.merge(base, nxt)
+
+    assert result == [{"bar": ["bob"]}, {"bar": ["baz"]}]

docs/conf.py

@@ -52,18 +52,18 @@
 master_doc = "index"
 
 # General information about the project.
-project = u"deepmerge"
-copyright = u"2016, Yusuke Tsutsumi"
-author = u"Yusuke Tsutsumi"
+project = "deepmerge"
+copyright = "2016, Yusuke Tsutsumi"
+author = "Yusuke Tsutsumi"
 
 # The version info for the project you're documenting, acts as replacement for
 # |version| and |release|, also used in various other places throughout the
 # built documents.
 #
 # The short X.Y version.
-version = u"0.1"
+version = "0.1"
 # The full version, including alpha/beta/rc tags.
-release = u"0.1"
+release = "0.1"
 
 # The language for content autogenerated by Sphinx. Refer to documentation
 # for a list of supported languages.
@@ -271,8 +271,8 @@
     (
         master_doc,
         "deepmerge.tex",
-        u"deepmerge Documentation",
-        u"Yusuke Tsutsumi",
+        "deepmerge Documentation",
+        "Yusuke Tsutsumi",
         "manual",
     ),
 ]
@@ -308,7 +308,7 @@
 
 # One entry per manual page. List of tuples
 # (source start file, name, description, authors, manual section).
-man_pages = [(master_doc, "deepmerge", u"deepmerge Documentation", [author], 1)]
+man_pages = [(master_doc, "deepmerge", "deepmerge Documentation", [author], 1)]
 
 # If true, show URL addresses after external links.
 #
@@ -324,7 +324,7 @@
     (
         master_doc,
         "deepmerge",
-        u"deepmerge Documentation",
+        "deepmerge Documentation",
         author,
         "deepmerge",
         "One line description of project.",

docs/guide.rst

@@ -10,7 +10,7 @@ it's recommended to choose your own strategies, deepmerge does
 provided some preconfigured mergers for a common situations:
 
 * deepmerge.always_merger: always try to merge. in the case of mismatches, the value from the second object overrides the first o ne.
-* deepmerge.merge_or_raise: try to merge, raise an exception if an unmergable situation is encountered. 
+* deepmerge.merge_or_raise: try to merge, raise an exception if an unmergable situation is encountered.
 * deepmerge.conservative_merger: similar to always_merger, but in the case of a conflict, use the existing value.
 
 Once a merger is constructed, it then has a merge() method that can be called:
@@ -33,7 +33,6 @@ Once a merger is constructed, it then has a merge() method that can be called:
 Merges are Destructive
 ======================
 
-
 You may have noticed from the example, but merging is a destructive behavior: it will modify the first argument passed in (the base) as part of the merge.
 
 This is intentional, as an implicit copy would result in a significant performance slowdown for deep data structures. If you need to keep the original objects unmodified, you can use the deepcopy method:
@@ -96,3 +95,13 @@ Example:
 If a strategy fails, an exception should not be raised. This is to
 ensure it can be chained with other strategies, or the fall-back.
 
+Uniqueness of elements when merging
+===================================
+
+Some strategies require determining the uniqueness
+of the elements. Since deepmerge primarily deals with nested
+types, this includes structures that are not hashable such as
+dictionaries.
+
+In those cases, built-in deepmerge strategies will call repr()
+on the object and hash that value instead.