next.js

7dc4cdd4 - Show inner `"use cache"` as cause of nested-dynamic cache error (#93707)

Show inner `"use cache"` as cause of nested-dynamic cache error (#93707) When a `"use cache"` propagated a dynamic cache life (`revalidate: 0` or `expire` under 5 minutes) to a parent without an explicit `cacheLife`, the resulting error pointed only at the outer cache invocation. With the inner cache's call site missing, tracing which nested cache was responsible meant reading through the outer's body — fine when it's local code, much harder when the dynamism comes from a nested cache buried in a third-party dependency. This change attaches the inner invocation as `cause` of the error, so the dev redbox and the build log show two stacks: the outer that threw, and the inner that propagated the dynamic life. The inner call site has to be captured eagerly while `cache()` is still on the synchronous stack, because we only learn whether the inner resolved dynamic asynchronously — after `collectResult` finishes and `propagateCacheEntryMetadata` runs — and by then the inner's frames are no longer on the JS stack. We only construct the eager `Error` when the parent is itself a public `"use cache"` (the only case where this entry could become a propagated origin), so top-level caches skip the allocation. The eager `Error` is held on `cacheContext.dynamicNestedCacheError`; once propagation knows the inner resolved dynamic, it's copied onto the outer store's same-named field, then carried through the outer's own `collectResult` into its RDC entry — which the throw site finally reads back as `cause`. We keep the first dynamic child — the immediate origin from the throwing cache's perspective. The two nested-dynamic cache error messages also get a small cleanup: each used to write `"use cache"` two different ways within the same sentence (bare and backticked); both now write it the same way. <img width="2188" height="2662" alt="localhost_3000_use-cache-low-expire_nested (1)" src="https://github.com/user-attachments/assets/f5103e0e-b9c0-44c5-b93b-82981aa05219" />