Python: Preserve messages when replacing chat history from itself

[黄耀鑫(Huang Yaoxin) (YaoxinHuang)]

Motivation and Context

ChatHistory.replace clears its messages before consuming the replacement iterable. Passing the history itself, its messages list, or a generator filtering the history therefore silently empties it. For example, removing assistant messages with history.replace(m for m in history if m.role != AuthorRole.ASSISTANT) also loses the system and user messages.

Description

Materialize the iterable before clearing the history, while preserving the existing messages list. Add regression coverage for the history, its backing list, an iterator, and a filtered generator.

Validated the contents unit suite, repository pre-commit hooks for both changed files, scoped mypy, and a wheel build. The full optional-provider test matrix was not run.

Contribution Checklist

• The code builds clean without any errors or warnings
• The PR follows the SK Contribution Guidelines and the pre-submission formatting script raises no violations
• All unit tests pass, and I have added new tests where possible
• I didn't break anyone 😄

[Copilot]

Copilot review overview

🟢 Approval recommended

Reviewed changes address the reported replacement behavior with regression coverage.

Review effort: Lite
Findings: None

What changed in this PR

Updates ChatHistory.replace to preserve messages when replacing history from itself or related iterables.

Changes:

• Materializes replacement messages before clearing history.
• Adds regression tests for histories, lists, iterators, and filtered generators.

File	Description
python/​tests/​unit/​contents/​test_chat_history.py	Adds regression coverage for self-referential replacements.
python/​semantic_kernel/​contents/​chat_history.py	Safely materializes replacement messages while preserving list identity.

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[黄耀鑫(Huang Yaoxin) (YaoxinHuang)]

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