What should a DRF partial update guarantee beyond accepting PATCH?

Defines omission, nullability, field ownership, invariants, concurrency, and effects for DRF partial updates.

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With a partial serializer, omitted fields keep their current value while submitted fields are validated and applied. An explicit null is different from omission and is allowed only when the contract permits it. The serializer must keep immutable and server-owned fields read-only, and the workflow must authorize each change rather than assuming permission to edit the object allows every field.

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Whether PATCH is treated as a deliberate update contract rather than automatic model mutation.

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A partial update must define which state may change and how omitted values differ from explicit values.
With a partial serializer, omitted fields keep their current value while submitted fields are validated and applied. An explicit null is different from omission and is allowed only when the contract permits it. The serializer must keep immutable and server-owned fields read-only, and the workflow must authorize each change rather than assuming permission to edit the object allows every field.
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Cross-field invariants still need the resulting state, not only the submitted subset. I merge or reason about existing values before accepting a combination, and I define whether updates trigger domain transitions or side effects. A write serializer should not blindly assign every validated key to the model. Tests cover omitted, null, unchanged, forbidden, and conflicting fields as separate cases.

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Treating omitted and explicit null values as the same.
Allowing every model field because partial=True is set.
Validating only submitted fields when invariants span old and new state.

What should a DRF partial update guarantee beyond accepting PATCH?

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