chore(sdk): update unset logic

[Eugene Yurtsev (eyurtsev)]

Update unset logic so that files_update can only be dict | None (not Unset)

[codspeed]

Merging this PR will not alter performance

✅ 32 untouched benchmarks
⏩ 15 skipped benchmarks¹

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_{Comparing eugene/update_unset_logic (6448794) with main (5b2893c)}

Footnotes

1. 15 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

[Copilot]

Pull request overview

This PR adjusts the deprecated files_update handling in backend result types so callers never observe the sentinel value and files_update is normalized to dict | None.

Changes:

• Introduces an Unset sentinel and _normalize_files_update() helper to convert the sentinel into None and emit the deprecation warning only when files_update is explicitly provided.
• Reworks WriteResult and EditResult to use @dataclass(init=False) with custom __init__, ensuring files_update is stored as dict | None (never _Unset).

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[Copilot]

files_update used to be excluded from the dataclass repr (it was declared with repr=False). With the new @dataclass(init=False) + plain annotation, files_update will now appear in WriteResult.__repr__, which can make logs noisy and potentially include large/sensitive data even though the field is deprecated. Consider restoring repr=False for files_update (e.g., by using a dataclass field with repr=False, while still normalizing the value in __init__).

[Copilot]

The sentinel is now exposed as a public module symbol named Unset. This is a new public API surface and the CamelCase name is easy to confuse with a type/class. If external callers aren’t expected to use it, consider keeping it private (e.g., _UNSET) or, if it is meant to be a constant, use an all-caps name to match typical constant conventions.