Fix: Preserve dict insertion order in assertion output

[hrideymarwah15]

Summary

This PR fixes issue #13503 by preserving dictionary insertion order in assertion failure output instead of sorting keys alphabetically.

Problem

Since Python 3.7+, dictionaries maintain insertion order. However, pytest's assertion output was sorting dictionary keys alphabetically, which:

• Doesn't match Python's native dict display behavior
• Makes debugging confusing when developers expect insertion order
• Provides misleading output for ordered data structures

Solution

Removed sorted() calls in the PrettyPrinter class:

• _pprint_dict method: Changed sorted(object.items(), key=_safe_tuple) to object.items()
• _safe_repr method: Changed sorted(object.items(), key=_safe_tuple) to object.items()

Changes

• Modified src/_pytest/_io/pprint.py to preserve dict insertion order (2 lines changed)
• Added test test_dict_preserves_insertion_order in testing/io/test_pprint.py (33 lines added)
• Allow maintainers to push and squash when merging

Example

Before:

assert {'z': 1, 'a': 2, 'm': 3} == {'z': 1, 'a': 3, 'm': 3}
# Output showed: {'a': 2, 'm': 3, 'z': 1} (alphabetical)

After:

assert {'z': 1, 'a': 2, 'm': 3} == {'z': 1, 'a': 3, 'm': 3}
# Output shows: {'z': 1, 'a': 2, 'm': 3} (insertion order)

Closes #13503

[Copilot]

Pull request overview

This PR fixes issue #13503 by preserving dictionary insertion order in assertion failure output instead of sorting keys alphabetically, aligning pytest's output with Python 3.7+ dict behavior.

Changes:

• Removed alphabetical sorting of dictionary keys in PrettyPrinter class methods
• Added test to verify insertion order preservation
• Added changelog entry documenting the bugfix

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
src/_pytest/_io/pprint.py	Removed sorted() calls in _pprint_dict and _safe_repr methods to preserve dict insertion order
testing/io/test_pprint.py	Added test_dict_preserves_insertion_order test to verify insertion order is maintained
changelog/13503.bugfix.rst	Added changelog entry documenting the bugfix

Comments suppressed due to low confidence (1)

src/_pytest/_io/pprint.py:37

• The docstring's last sentence mentions 'dict.items() must have _safe_key applied' which is now outdated since the PR removes sorting from dict items. While _safe_key is still used for sets (line 239), the documentation should be clarified to avoid confusion. Consider updating to: 'Does not work recursively, so for collections that are sorted (like sets), both key and value must have _safe_key applied.'

class _safe_key:
    """Helper function for key functions when sorting unorderable objects.

    The wrapped-object will fallback to a Py2.x style comparison for
    unorderable types (sorting first comparing the type name and then by
    the obj ids).  Does not work recursively, so dict.items() must have
    _safe_key applied to both the key and the value.

    """

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[nicoddemus]

Thanks, but duplicate of #14066.