next.js

91eb8316 - Trace-server: Fix bottom up, and reduce allocations in turbopack-trace-server bottom-up grouping (#93460)

Trace-server: Fix bottom up, and reduce allocations in turbopack-trace-server bottom-up grouping (#93460) ### What? Speeds up the bottom-up grouping pass in `turbopack-trace-server` by removing per-span `RcStr` allocations and fixes the hash map using the correct hasher for the grouping `HashMap`. ### Why? When loading large traces, building the bottom-up graph spent measurable time (1) allocating fresh `RcStr` values from `&str` keys for every span just to use them as `HashMap` keys, and (2) hashing those keys with the default randomized hasher. Both are avoidable: the underlying spans already own `RcStr`s, and the `StringTupleRef` equivalence-based lookup needs `FxHasher` anyway because `RcStr`'s `Hash` impl only matches `&str`'s `Hash` under `FxHasher`. ### How? - Change `nice_name`/`group_name`/`args` accessors on `SpanRef` and friends to return `&RcStr` instead of `&str`. The bottom-up grouping code can now clone the existing `RcStr` (a cheap ref-count bump) instead of allocating a new one from a `&str`. - Switch the `(RcStr, RcStr) -> SpanBottomUpBuilder` map in `bottom_up.rs` to use `FxBuildHasher`. This is required for the `StringTupleRef` equivalence lookup to produce matching hashes for the owned `(RcStr, RcStr)` keys, and it also removes the overhead of the default randomized hasher. - Update the `string_tuple_ref` test to use `FxBuildHasher` accordingly. No behavior changes; this is a pure refactor for performance inside the trace viewer tool. <!-- NEXT_JS_LLM_PR -->