Issue 5381: Add object_pairs_hook to the json module.

Lib/json/__init__.py

@@ -238,11 +238,12 @@ def dumps(obj, skipkeys=False, ensure_ascii=True, check_circular=True,
         **kw).encode(obj)
 
 
-_default_decoder = JSONDecoder(encoding=None, object_hook=None)
+_default_decoder = JSONDecoder(encoding=None, object_hook=None,
+                               object_pairs_hook=None)
 
 
 def load(fp, encoding=None, cls=None, object_hook=None, parse_float=None,
-        parse_int=None, parse_constant=None, **kw):
+        parse_int=None, parse_constant=None, object_pairs_hook=None, **kw):
     """Deserialize ``fp`` (a ``.read()``-supporting file-like object containing
     a JSON document) to a Python object.
 
@@ -265,11 +266,11 @@ def load(fp, encoding=None, cls=None, object_hook=None, parse_float=None,
     return loads(fp.read(),
         encoding=encoding, cls=cls, object_hook=object_hook,
         parse_float=parse_float, parse_int=parse_int,
-        parse_constant=parse_constant, **kw)
+        parse_constant=parse_constant, object_pairs_hook=None, **kw)
 
 
 def loads(s, encoding=None, cls=None, object_hook=None, parse_float=None,
-        parse_int=None, parse_constant=None, **kw):
+        parse_int=None, parse_constant=None, object_pairs_hook=None, **kw):
     """Deserialize ``s`` (a ``str`` or ``unicode`` instance containing a JSON
     document) to a Python object.
 
@@ -304,12 +305,14 @@ def loads(s, encoding=None, cls=None, object_hook=None, parse_float=None,
     """
     if (cls is None and encoding is None and object_hook is None and
             parse_int is None and parse_float is None and
-            parse_constant is None and not kw):
+            parse_constant is None and object_pairs_hook is None and not kw):
         return _default_decoder.decode(s)
     if cls is None:
         cls = JSONDecoder
     if object_hook is not None:
         kw['object_hook'] = object_hook
+    if object_pairs_hook is not None:
+        kw['object_pairs_hook'] = object_pairs_hook
     if parse_float is not None:
         kw['parse_float'] = parse_float
     if parse_int is not None:

Lib/json/decoder.py

@@ -147,8 +147,9 @@ WHITESPACE = re.compile(r'[ \t\n\r]*', FLAGS)
 WHITESPACE_STR = ' \t\n\r'
 
 def JSONObject((s, end), encoding, strict, scan_once, object_hook,
-        _w=WHITESPACE.match, _ws=WHITESPACE_STR):
-    pairs = {}
+               object_pairs_hook, _w=WHITESPACE.match, _ws=WHITESPACE_STR):
+    pairs = []
+    pairs_append = pairs.append
     # Use a slice to prevent IndexError from being raised, the following
     # check will raise a more specific ValueError if the string is empty
     nextchar = s[end:end + 1]
@@ -187,7 +188,7 @@ def JSONObject((s, end), encoding, strict, scan_once, object_hook,
             value, end = scan_once(s, end)
         except StopIteration:
             raise ValueError(errmsg("Expecting object", s, end))
-        pairs[key] = value
+        pairs_append((key, value))
 
         try:
             nextchar = s[end]
@@ -218,6 +219,10 @@ def JSONObject((s, end), encoding, strict, scan_once, object_hook,
         if nextchar != '"':
             raise ValueError(errmsg("Expecting property name", s, end - 1))
 
+    if object_pairs_hook is not None:
+        result = object_pairs_hook(pairs)
+        return result, end
+    pairs = dict(pairs)
     if object_hook is not None:
         pairs = object_hook(pairs)
     return pairs, end
@@ -289,7 +294,8 @@ class JSONDecoder(object):
     """
 
     def __init__(self, encoding=None, object_hook=None, parse_float=None,
-            parse_int=None, parse_constant=None, strict=True):
+            parse_int=None, parse_constant=None, strict=True,
+            object_pairs_hook=None):
         """``encoding`` determines the encoding used to interpret any ``str``
         objects decoded by this instance (utf-8 by default).  It has no
         effect when decoding ``unicode`` objects.
@@ -320,6 +326,7 @@ class JSONDecoder(object):
         """
         self.encoding = encoding
         self.object_hook = object_hook
+        self.object_pairs_hook = object_pairs_hook
         self.parse_float = parse_float or float
         self.parse_int = parse_int or int
         self.parse_constant = parse_constant or _CONSTANTS.__getitem__

Lib/json/tests/test_decode.py

@@ -2,6 +2,7 @@ import decimal
 from unittest import TestCase
 
 import json
+from collections import OrderedDict
 
 class TestDecode(TestCase):
     def test_decimal(self):
@@ -20,3 +21,18 @@ class TestDecode(TestCase):
         # exercise the uncommon cases. The array cases are already covered.
         rval = json.loads('{   "key"    :    "value"    ,  "k":"v"    }')
         self.assertEquals(rval, {"key":"value", "k":"v"})
+
+    def test_object_pairs_hook(self):
+        s = '{"xkd":1, "kcw":2, "art":3, "hxm":4, "qrt":5, "pad":6, "hoy":7}'
+        p = [("xkd", 1), ("kcw", 2), ("art", 3), ("hxm", 4),
+             ("qrt", 5), ("pad", 6), ("hoy", 7)]
+        self.assertEqual(json.loads(s), eval(s))
+        self.assertEqual(json.loads(s, object_pairs_hook = lambda x: x), p)
+        od = json.loads(s, object_pairs_hook = OrderedDict)
+        self.assertEqual(od, OrderedDict(p))
+        self.assertEqual(type(od), OrderedDict)
+        # the object_pairs_hook takes priority over the object_hook
+        self.assertEqual(json.loads(s,
+                                    object_pairs_hook = OrderedDict,
+                                    object_hook = lambda x: None),
+                         OrderedDict(p))

Lib/json/tests/test_unicode.py

@@ -1,6 +1,7 @@
 from unittest import TestCase
 
 import json
+from collections import OrderedDict
 
 class TestUnicode(TestCase):
     def test_encoding1(self):
@@ -54,6 +55,21 @@ class TestUnicode(TestCase):
             s = '"\\u{0:04x}"'.format(i)
             self.assertEquals(json.loads(s), u)
 
+    def test_object_pairs_hook_with_unicode(self):
+        s = u'{"xkd":1, "kcw":2, "art":3, "hxm":4, "qrt":5, "pad":6, "hoy":7}'
+        p = [(u"xkd", 1), (u"kcw", 2), (u"art", 3), (u"hxm", 4),
+             (u"qrt", 5), (u"pad", 6), (u"hoy", 7)]
+        self.assertEqual(json.loads(s), eval(s))
+        self.assertEqual(json.loads(s, object_pairs_hook = lambda x: x), p)
+        od = json.loads(s, object_pairs_hook = OrderedDict)
+        self.assertEqual(od, OrderedDict(p))
+        self.assertEqual(type(od), OrderedDict)
+        # the object_pairs_hook takes priority over the object_hook
+        self.assertEqual(json.loads(s,
+                                    object_pairs_hook = OrderedDict,
+                                    object_hook = lambda x: None),
+                         OrderedDict(p))
+
     def test_default_encoding(self):
         self.assertEquals(json.loads(u'{"a": "\xe9"}'.encode('utf-8')),
             {'a': u'\xe9'})