Issue #14386: Expose the dict_proxy internal type as types.MappingProxyType

3 files changed, 184 insertions, 5 deletions

diff --git a/Lib/test/test_descr.py b/Lib/test/test_descr.py
index 3051e57..c0c7414 100644
--- a/Lib/test/test_descr.py
+++ b/Lib/test/test_descr.py
@@ -4574,11 +4574,11 @@ class DictProxyTests(unittest.TestCase):
         self.assertEqual(type(C.__dict__), type(B.__dict__))
 
     def test_repr(self):
-        # Testing dict_proxy.__repr__.
+        # Testing mappingproxy.__repr__.
         # We can't blindly compare with the repr of another dict as ordering
         # of keys and values is arbitrary and may differ.
         r = repr(self.C.__dict__)
-        self.assertTrue(r.startswith('dict_proxy('), r)
+        self.assertTrue(r.startswith('mappingproxy('), r)
         self.assertTrue(r.endswith(')'), r)
         for k, v in self.C.__dict__.items():
             self.assertIn('{!r}: {!r}'.format(k, v), r)
diff --git a/Lib/test/test_types.py b/Lib/test/test_types.py
index 8a98a03..9a2e0d4 100644
--- a/Lib/test/test_types.py
+++ b/Lib/test/test_types.py
@@ -1,9 +1,11 @@
 # Python test set -- part 6, built-in types
 
 from test.support import run_unittest, run_with_locale
-import unittest
-import sys
+import collections
 import locale
+import sys
+import types
+import unittest
 
 class TypesTests(unittest.TestCase):
 
@@ -569,8 +571,184 @@ class TypesTests(unittest.TestCase):
         self.assertGreater(tuple.__itemsize__, 0)
 
 
+class MappingProxyTests(unittest.TestCase):
+    mappingproxy = types.MappingProxyType
+
+    def test_constructor(self):
+        class userdict(dict):
+            pass
+
+        mapping = {'x': 1, 'y': 2}
+        self.assertEqual(self.mappingproxy(mapping), mapping)
+        mapping = userdict(x=1, y=2)
+        self.assertEqual(self.mappingproxy(mapping), mapping)
+        mapping = collections.ChainMap({'x': 1}, {'y': 2})
+        self.assertEqual(self.mappingproxy(mapping), mapping)
+
+        self.assertRaises(TypeError, self.mappingproxy, 10)
+        self.assertRaises(TypeError, self.mappingproxy, ("a", "tuple"))
+        self.assertRaises(TypeError, self.mappingproxy, ["a", "list"])
+
+    def test_methods(self):
+        attrs = set(dir(self.mappingproxy({}))) - set(dir(object()))
+        self.assertEqual(attrs, {
+             '__contains__',
+             '__getitem__',
+             '__iter__',
+             '__len__',
+             'copy',
+             'get',
+             'items',
+             'keys',
+             'values',
+        })
+
+    def test_get(self):
+        view = self.mappingproxy({'a': 'A', 'b': 'B'})
+        self.assertEqual(view['a'], 'A')
+        self.assertEqual(view['b'], 'B')
+        self.assertRaises(KeyError, view.__getitem__, 'xxx')
+        self.assertEqual(view.get('a'), 'A')
+        self.assertIsNone(view.get('xxx'))
+        self.assertEqual(view.get('xxx', 42), 42)
+
+    def test_missing(self):
+        class dictmissing(dict):
+            def __missing__(self, key):
+                return "missing=%s" % key
+
+        view = self.mappingproxy(dictmissing(x=1))
+        self.assertEqual(view['x'], 1)
+        self.assertEqual(view['y'], 'missing=y')
+        self.assertEqual(view.get('x'), 1)
+        self.assertEqual(view.get('y'), None)
+        self.assertEqual(view.get('y', 42), 42)
+        self.assertTrue('x' in view)
+        self.assertFalse('y' in view)
+
+    def test_customdict(self):
+        class customdict(dict):
+            def __contains__(self, key):
+                if key == 'magic':
+                    return True
+                else:
+                    return dict.__contains__(self, key)
+
+            def __iter__(self):
+                return iter(('iter',))
+
+            def __len__(self):
+                return 500
+
+            def copy(self):
+                return 'copy'
+
+            def keys(self):
+                return 'keys'
+
+            def items(self):
+                return 'items'
+
+            def values(self):
+                return 'values'
+
+            def __getitem__(self, key):
+                return "getitem=%s" % dict.__getitem__(self, key)
+
+            def get(self, key, default=None):
+                return "get=%s" % dict.get(self, key, 'default=%r' % default)
+
+        custom = customdict({'key': 'value'})
+        view = self.mappingproxy(custom)
+        self.assertTrue('key' in view)
+        self.assertTrue('magic' in view)
+        self.assertFalse('xxx' in view)
+        self.assertEqual(view['key'], 'getitem=value')
+        self.assertRaises(KeyError, view.__getitem__, 'xxx')
+        self.assertEqual(tuple(view), ('iter',))
+        self.assertEqual(len(view), 500)
+        self.assertEqual(view.copy(), 'copy')
+        self.assertEqual(view.get('key'), 'get=value')
+        self.assertEqual(view.get('xxx'), 'get=default=None')
+        self.assertEqual(view.items(), 'items')
+        self.assertEqual(view.keys(), 'keys')
+        self.assertEqual(view.values(), 'values')
+
+    def test_chainmap(self):
+        d1 = {'x': 1}
+        d2 = {'y': 2}
+        mapping = collections.ChainMap(d1, d2)
+        view = self.mappingproxy(mapping)
+        self.assertTrue('x' in view)
+        self.assertTrue('y' in view)
+        self.assertFalse('z' in view)
+        self.assertEqual(view['x'], 1)
+        self.assertEqual(view['y'], 2)
+        self.assertRaises(KeyError, view.__getitem__, 'z')
+        self.assertEqual(tuple(sorted(view)), ('x', 'y'))
+        self.assertEqual(len(view), 2)
+        copy = view.copy()
+        self.assertIsNot(copy, mapping)
+        self.assertIsInstance(copy, collections.ChainMap)
+        self.assertEqual(copy, mapping)
+        self.assertEqual(view.get('x'), 1)
+        self.assertEqual(view.get('y'), 2)
+        self.assertIsNone(view.get('z'))
+        self.assertEqual(tuple(sorted(view.items())), (('x', 1), ('y', 2)))
+        self.assertEqual(tuple(sorted(view.keys())), ('x', 'y'))
+        self.assertEqual(tuple(sorted(view.values())), (1, 2))
+
+    def test_contains(self):
+        view = self.mappingproxy(dict.fromkeys('abc'))
+        self.assertTrue('a' in view)
+        self.assertTrue('b' in view)
+        self.assertTrue('c' in view)
+        self.assertFalse('xxx' in view)
+
+    def test_views(self):
+        mapping = {}
+        view = self.mappingproxy(mapping)
+        keys = view.keys()
+        values = view.values()
+        items = view.items()
+        self.assertEqual(list(keys), [])
+        self.assertEqual(list(values), [])
+        self.assertEqual(list(items), [])
+        mapping['key'] = 'value'
+        self.assertEqual(list(keys), ['key'])
+        self.assertEqual(list(values), ['value'])
+        self.assertEqual(list(items), [('key', 'value')])
+
+    def test_len(self):
+        for expected in range(6):
+            data = dict.fromkeys('abcde'[:expected])
+            self.assertEqual(len(data), expected)
+            view = self.mappingproxy(data)
+            self.assertEqual(len(view), expected)
+
+    def test_iterators(self):
+        keys = ('x', 'y')
+        values = (1, 2)
+        items = tuple(zip(keys, values))
+        view = self.mappingproxy(dict(items))
+        self.assertEqual(set(view), set(keys))
+        self.assertEqual(set(view.keys()), set(keys))
+        self.assertEqual(set(view.values()), set(values))
+        self.assertEqual(set(view.items()), set(items))
+
+    def test_copy(self):
+        original = {'key1': 27, 'key2': 51, 'key3': 93}
+        view = self.mappingproxy(original)
+        copy = view.copy()
+        self.assertEqual(type(copy), dict)
+        self.assertEqual(copy, original)
+        original['key1'] = 70
+        self.assertEqual(view['key1'], 70)
+        self.assertEqual(copy['key1'], 27)
+
+
 def test_main():
-    run_unittest(TypesTests)
+    run_unittest(TypesTests, MappingProxyTests)
 
 if __name__ == '__main__':
     test_main()
diff --git a/Lib/types.py b/Lib/types.py
index ab354d1..08cbb83 100644
--- a/Lib/types.py
+++ b/Lib/types.py
@@ -12,6 +12,7 @@ def _f(): pass
 FunctionType = type(_f)
 LambdaType = type(lambda: None)         # Same as FunctionType
 CodeType = type(_f.__code__)
+MappingProxyType = type(type.__dict__)
 
 def _g():
     yield 1