perf(hmr): remove unnecessary string allocations#10422
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Pull request overview
This PR optimizes HMR AST construction by avoiding arena allocations when converting 'static string literals into Oxc Str, using Str::from (borrowed, zero-cost) instead of Str::from_str_in (arena-allocating). This follows the earlier AST construction migration work and continues the string-allocation cleanup in the HMR path.
Changes:
- Replace
from_str_inwithStr::fromfor'staticstring literals in HMR AST builder helpers. - Avoid arena allocations for template literal quasi
rawstrings used to build the/@vite/lazy?...URL in the HMR lazy proxy rewrite.
Reviewed changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.
| File | Description |
|---|---|
| crates/rolldown/src/hmr/utils.rs | Uses ast::Str::from for a 'static module exports binding name to avoid arena allocation. |
| crates/rolldown/src/hmr/hmr_ast_finalizer.rs | Uses Str::from for 'static template literal quasi strings to avoid arena allocation in lazy proxy URL construction. |
Merging this PR will not alter performance
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Follow-on after #10018, continuation of #10420 and #10421. When converting `&'static str`s to `Str`s, use `Str::from` instead of `Str::from_str_in`. The difference is that `from_str_in` performs an allocation (in arena), whereas `from` is a zero-cost no-op conversion at runtime. When the `&str` already has a `'static` lifetime, it's unnecessary to extend it by allocating it into arena. Before: ```rs TemplateElementValue { raw: Str::from_str_in("/@vite/lazy?id=", &self.ast_builder), cooked: None, } ``` After: ```rs TemplateElementValue { raw: Str::from("/@vite/lazy?id="), cooked: None } ```
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Follow-on after #10018, continuation of #10420 and #10421.
When converting
&'static strs toStrs, useStr::frominstead ofStr::from_str_in. The difference is thatfrom_str_inperforms an allocation (in arena), whereasfromis a zero-cost no-op conversion at runtime. When the&stralready has a'staticlifetime, it's unnecessary to extend it by allocating it into arena.Before:
After: