fix: display output failure message in insertion order of dictionary

Author: ritvi-alagusankar

src/_pytest/_io/pprint.py

@@ -62,6 +62,7 @@ def __init__(
         indent: int = 4,
         width: int = 80,
         depth: int | None = None,
+        sort_dicts: bool = True,
     ) -> None:
         """Handle pretty printing operations onto a stream using a set of
         configured parameters.
@@ -74,6 +75,9 @@ def __init__(
 
         depth
             The maximum depth to print out nested structures.
+        
+        sort_dicts
+            If true, dict keys are sorted.
 
         """
         if indent < 0:
@@ -85,6 +89,7 @@ def __init__(
         self._depth = depth
         self._indent_per_level = indent
         self._width = width
+        self._sort_dicts = sort_dicts
 
     def pformat(self, object: Any) -> str:
         sio = _StringIO()
@@ -162,7 +167,10 @@ def _pprint_dict(
     ) -> None:
         write = stream.write
         write("{")
-        items = sorted(object.items(), key=_safe_tuple)
+        if self._sort_dicts:
+            items = sorted(object.items(), key=_safe_tuple)
+        else:
+            items = object.items()
         self._format_dict_items(items, stream, indent, allowance, context, level)
         write("}")
 
@@ -608,7 +616,11 @@ def _safe_repr(
             components: list[str] = []
             append = components.append
             level += 1
-            for k, v in sorted(object.items(), key=_safe_tuple):
+            if self._sort_dicts:
+                items = sorted(object.items(), key=_safe_tuple)
+            else:
+                items = object.items()
+            for k, v in items:
                 krepr = self._safe_repr(k, context, maxlevels, level)
                 vrepr = self._safe_repr(v, context, maxlevels, level)
                 append(f"{krepr}: {vrepr}")

src/_pytest/assertion/util.py

@@ -348,8 +348,8 @@ def _compare_eq_iterable(
     # dynamic import to speedup pytest
     import difflib
 
-    left_formatting = PrettyPrinter().pformat(left).splitlines()
-    right_formatting = PrettyPrinter().pformat(right).splitlines()
+    left_formatting = PrettyPrinter(sort_dicts=False).pformat(left).splitlines()
+    right_formatting = PrettyPrinter(sort_dicts=False).pformat(right).splitlines()
 
     explanation = ["", "Full diff:"]
     # "right" is the expected base against which we compare "left",
@@ -505,29 +505,32 @@ def _compare_eq_dict(
     set_left = set(left)
     set_right = set(right)
     common = set_left.intersection(set_right)
-    same = {k: left[k] for k in common if left[k] == right[k]}
+    same = {k: left[k] for k in left if k in right and left[k] == right[k]}
     if same and verbose < 2:
         explanation += [f"Omitting {len(same)} identical items, use -vv to show"]
     elif same:
         explanation += ["Common items:"]
-        explanation += highlighter(pprint.pformat(same)).splitlines()
+        # Common items are displayed in the order of the left dict
+        explanation += highlighter(pprint.pformat(same, sort_dicts=False)).splitlines()
     diff = {k for k in common if left[k] != right[k]}
     if diff:
         explanation += ["Differing items:"]
-        for k in diff:
-            explanation += [
-                highlighter(saferepr({k: left[k]}))
-                + " != "
-                + highlighter(saferepr({k: right[k]}))
-            ]
+        # Differing items are displayed in the order of the left dict
+        for k in left:
+            if k in diff:
+                explanation += [
+                    highlighter(saferepr({k: left[k]}))
+                    + " != "
+                    + highlighter(saferepr({k: right[k]}))
+                ]
     extra_left = set_left - set_right
     len_extra_left = len(extra_left)
     if len_extra_left:
         explanation.append(
             f"Left contains {len_extra_left} more item{'' if len_extra_left == 1 else 's'}:"
         )
         explanation.extend(
-            highlighter(pprint.pformat({k: left[k] for k in extra_left})).splitlines()
+            highlighter(pprint.pformat({k: left[k] for k in left if k in extra_left}, sort_dicts=False)).splitlines()
         )
     extra_right = set_right - set_left
     len_extra_right = len(extra_right)
@@ -536,7 +539,7 @@ def _compare_eq_dict(
             f"Right contains {len_extra_right} more item{'' if len_extra_right == 1 else 's'}:"
         )
         explanation.extend(
-            highlighter(pprint.pformat({k: right[k] for k in extra_right})).splitlines()
+            highlighter(pprint.pformat({k: right[k] for k in right if k in extra_right}, sort_dicts=False)).splitlines()
         )
     return explanation
 

testing/test_error_diffs.py

@@ -198,6 +198,70 @@ def test_this():
         """,
         id="Compare dicts with differing items",
     ),
+    pytest.param(
+        """
+        def test_this():
+            result = {'d': 4, 'c': 3, 'b': 2, 'a': 1}
+            expected = {'d': 4, 'c': 3, 'e': 5}
+            assert result == expected
+        """,
+        """
+        >       assert result == expected
+        E       AssertionError: assert {'d': 4, 'c': 3, 'b': 2, 'a': 1} == {'d': 4, 'c': 3, 'e': 5}
+        E         
+        E         Common items:
+        E         {'d': 4, 'c': 3}
+        E         Left contains 2 more items:
+        E         {'b': 2, 'a': 1}
+        E         Right contains 1 more item:
+        E         {'e': 5}
+        E         
+        E         Full diff:
+        E           {
+        E               'd': 4,
+        E               'c': 3,
+        E         -     'e': 5,
+        E         ?      ^   ^
+        E         +     'b': 2,
+        E         ?      ^   ^
+        E         +     'a': 1,
+        E           }
+        """,
+        id="Compare dicts and check order of diff",
+    ),
+    pytest.param(
+        """
+        def test_this():
+            result = {'c': 3, 'd': 4, 'b': 2, 'a': 1}
+            expected = {'d': 5, 'c': 3, 'b': 1}
+            assert result == expected
+        """,
+        """
+        >       assert result == expected
+        E       AssertionError: assert {'c': 3, 'd': 4, 'b': 2, 'a': 1} == {'d': 5, 'c': 3, 'b': 1}
+        E         
+        E         Common items:
+        E         {'c': 3}
+        E         Differing items:
+        E         {'d': 4} != {'d': 5}
+        E         {'b': 2} != {'b': 1}
+        E         Left contains 1 more item:
+        E         {'a': 1}
+        E         
+        E         Full diff:
+        E           {
+        E         -     'd': 5,
+        E               'c': 3,
+        E         +     'd': 4,
+        E         -     'b': 1,
+        E         ?          ^
+        E         +     'b': 2,
+        E         ?          ^
+        E         +     'a': 1,
+        E           }
+        """,
+        id="Compare dicts with different order and values",
+    ),
     pytest.param(
         """
         def test_this():