Function whyUpdated

whyUpdated<T>(
    commit: CommitForDecoding,
    _prev: ResourceState<T>,
    _next: ResourceState<T>,
): ResourceUpdateReason
Decode the reason a resource node was updated by a commit. Returns one of the seven ResourceUpdateReason values.
Type Parameters
- T
Parameters
- commit: CommitForDecoding
  the CommitForDecoding (carries the intent label the resource adapter sets per chart edge).
- _prev: ResourceState<T>
- _next: ResourceState<T>
Returns ResourceUpdateReason
Remarks
The decoder is a pure function: same inputs produce same outputs, no side effects, no graph reads. The decision tree:
1. If the intent prefix is one of the resource adapter's known labels (fetch:*:start, fetch:*:loaded, fetch:*:stale, fetch:*:error, invalidate:*, fail:*), return the matching reason.
2. Otherwise (the commit was on a different node and a downstream derived's recompute carried the resource into the changed-set), return 'dep-changed'.
The pre/post arms are not strictly required for any single decode step — the intent label suffices — but they are accepted in the signature so a future schema-bump that needs cross-arm disambiguation does not break adopter call sites.
- Defined in packages/sync/src/whyUpdated.ts:111