bpo-39994: Fix pprint handling of dict subclasses that override __repr__ (GH-21892)

Co-authored-by: Palak Kumar Jha

Lib/pprint.py

@@ -176,12 +176,6 @@ class PrettyPrinter:
                 p(self, object, stream, indent, allowance, context, level + 1)
                 del context[objid]
                 return
-            elif isinstance(object, dict):
-                context[objid] = 1
-                self._pprint_dict(object, stream, indent, allowance,
-                                  context, level + 1)
-                del context[objid]
-                return
         stream.write(rep)
 
     _dispatch = {}

Lib/test/test_pprint.py

@@ -18,6 +18,10 @@ class list3(list):
     def __repr__(self):
         return list.__repr__(self)
 
+class list_custom_repr(list):
+    def __repr__(self):
+        return '*'*len(list.__repr__(self))
+
 class tuple2(tuple):
     pass
 
@@ -25,6 +29,10 @@ class tuple3(tuple):
     def __repr__(self):
         return tuple.__repr__(self)
 
+class tuple_custom_repr(tuple):
+    def __repr__(self):
+        return '*'*len(tuple.__repr__(self))
+
 class set2(set):
     pass
 
@@ -32,6 +40,10 @@ class set3(set):
     def __repr__(self):
         return set.__repr__(self)
 
+class set_custom_repr(set):
+    def __repr__(self):
+        return '*'*len(set.__repr__(self))
+
 class frozenset2(frozenset):
     pass
 
@@ -39,6 +51,10 @@ class frozenset3(frozenset):
     def __repr__(self):
         return frozenset.__repr__(self)
 
+class frozenset_custom_repr(frozenset):
+    def __repr__(self):
+        return '*'*len(frozenset.__repr__(self))
+
 class dict2(dict):
     pass
 
@@ -46,6 +62,10 @@ class dict3(dict):
     def __repr__(self):
         return dict.__repr__(self)
 
+class dict_custom_repr(dict):
+    def __repr__(self):
+        return '*'*len(dict.__repr__(self))
+
 class Unorderable:
     def __repr__(self):
         return str(id(self))
@@ -155,7 +175,8 @@ class QueryTestCase(unittest.TestCase):
                              "expected not isreadable for %r" % (unreadable,))
 
     def test_same_as_repr(self):
-        # Simple objects, small containers and classes that overwrite __repr__
+        # Simple objects, small containers and classes that override __repr__
+        # to directly call super's __repr__.
         # For those the result should be the same as repr().
         # Ahem.  The docs don't say anything about that -- this appears to
         # be testing an implementation quirk.  Starting in Python 2.5, it's
@@ -187,6 +208,32 @@ class QueryTestCase(unittest.TestCase):
                              .replace('\n', ' '), native)
             self.assertEqual(pprint.saferepr(simple), native)
 
+    def test_container_repr_override_called(self):
+        N = 1000
+        # Ensure that __repr__ override is called for subclasses of containers
+
+        for cont in (list_custom_repr(),
+                     list_custom_repr([1,2,3]),
+                     list_custom_repr(range(N)),
+                     tuple_custom_repr(),
+                     tuple_custom_repr([1,2,3]),
+                     tuple_custom_repr(range(N)),
+                     set_custom_repr(),
+                     set_custom_repr([1,2,3]),
+                     set_custom_repr(range(N)),
+                     frozenset_custom_repr(),
+                     frozenset_custom_repr([1,2,3]),
+                     frozenset_custom_repr(range(N)),
+                     dict_custom_repr(),
+                     dict_custom_repr({5: 6}),
+                     dict_custom_repr(zip(range(N),range(N))),
+                    ):
+            native = repr(cont)
+            expected = '*' * len(native)
+            self.assertEqual(pprint.pformat(cont), expected)
+            self.assertEqual(pprint.pformat(cont, width=1, indent=0), expected)
+            self.assertEqual(pprint.saferepr(cont), expected)
+
     def test_basic_line_wrap(self):
         # verify basic line-wrapping operation
         o = {'RPM_cal': 0,

Misc/ACKS

@@ -856,6 +856,7 @@ Per Øyvind Karlsen
 Anton Kasyanov
 Lou Kates
 Makoto Kato
+Irit Katriel
 Hiroaki Kawai
 Dmitry Kazakov
 Brian Kearns

Misc/NEWS.d/next/Library/2020-08-15-18-17-21.bpo-39994.dOgPOh.rst

@@ -0,0 +1 @@
+Fixed pprint's handling of dict subclasses that override __repr__.