chore: Bump terser #4791
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chore: Bump terser #4791
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rschristian
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📊 Tachometer Benchmark ResultsSummaryduration
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rschristian
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rschristian
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Jun 7, 2025
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| // @ts-expect-error TODO: Legitimate type mismatch that our use of `NULL` hid | ||
| oldVNode ? oldVNode._dom : parentDom.firstChild, |
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This is a weird one. Above, we have this:
let oldVNode = isHydrating ? NULL : parentDom._children;For whatever reason, type inference has failed for NULL, so oldVNode was actually any. As such, this is a legitimate (internal) type mismatch in what diff expects as a parameter and what we provide. Will fix separately.
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Terser was locked in #4687 as we saw significant perf degradation from bumping the version further. Upon further investigation, it turns out this was due to a lack of hoisting:
In our CJS & ESM builds,
NULL&UNDEFINEDare not hoisted as constants but inlined throughout the bundle. For reasons that I still don't quite understand, hoisting these two, as newer versions of Terser will do, is a huge perf issue for us, causing double-digit regressions across the board. The byte impact is completely overshadowed by the perf hit, so, I've removed theNULL&UNDEFINEDconstants. We'll go back to usingnull&undefined/void 0throughout the source.Namespaces are a similar story; right now they're inlined, newer versions of Terser will hoist, but this is a very tiny byte reduction (we reference Math only once and XHTML & SVG twice each) with a 1-4% perf degradation in a few tests. Inlining them too seems better.
Edit: The perf regression is much larger w/ JIT enabled, disable it & hoisting is a slight improvement in some, still a regression in others. Not that it matters much ofc, just an interesting tidbit.
Therefore, the only real changes of this PR are as follows:
versionis now hoisted too, instead of inlined into the CJS exports. Harder to fix (or at least, I'm not sure how to) as we don't easily control how the exports are generated.exports.version = '18.3.1'has becomeexports.version = PNo worries if we want to just stick w/ older Terser, I mostly did this as an exploration as I was curious. There's no definite advantage here (I could go bench UMD builds I suppose though), just refactoring us so new Terser lines up with our old Terser output.