fix: enable arbitrary_precision for serde_json to fix JSON float parsing#8848
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IWANABETHATGUY merged 3 commits intorolldown:mainfrom Mar 22, 2026
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serde_json's default float parser produces off-by-one ULP errors for some 17-significant-digit floats (e.g. 114.35143799257997 is parsed to a different f64 than the correct nearest value). This causes JSON-imported numbers to silently change value after bundling. Enabling the `arbitrary_precision` feature makes serde_json preserve the raw number string internally, and `as_f64()` then uses Rust's standard `str::parse::<f64>()` which correctly rounds to the nearest IEEE 754 value. Fixes: vitejs/vite#21982 Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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Thanks, I simplified the test case a little.
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## [1.0.0-rc.11] - 2026-03-23 ### 🚀 Features - magicString replace with regex (#8802) by @IWANABETHATGUY - support `output.sourcemapExcludeSources` option (#8828) by @sapphi-red - support `getIndentString` in MagicString (#8775) by @IWANABETHATGUY - MagicString ignoreList support (#8773) by @IWANABETHATGUY ### 🐛 Bug Fixes - types: remove `pluginName` from `MinimalPluginContext` (#8864) by @sapphi-red - do not report eval?.() as direct eval (#8860) by @IWANABETHATGUY - handle negative indices, overlapping ranges, and moved content in MagicString remove (#8829) by @IWANABETHATGUY - enable arbitrary_precision for serde_json to fix JSON float parsing (#8848) by @elderapo - resolve TypeScript lint errors (#8841) by @Boshen - avoid panic on multi-byte UTF-8 chars in hash placeholder iterator (#8790) by @shulaoda - ci: skip failing vite build watch raw query test (#8840) by @Boshen - ci: use step-level env override to unset VITE_PLUS_CLI_BIN in vite tests (#8838) by @Boshen - ci: move vite tests into CI workflow by @Boshen - ci: unset all VITE_PLUS_* env vars in vite-tests workflow (#8837) by @Boshen - test: skip watch CLI tests on Windows (#8830) by @Boshen - ci: unset VITE_PLUS_CLI_BIN in vite-tests workflow (#8832) by @Boshen - remove redundant bare side-effect imports in entry/facade chunks (#8804) by @h-a-n-a - magicString prepend issues (#8797) by @IWANABETHATGUY - ci: use `vpx` instead of `vp exec` for `pkg-pr-new` (#8827) by @Boshen - set `order` for callable plugins (#8815) by @sapphi-red - handle reversed slice ranges with moved content (#8750) by @IWANABETHATGUY - update emnapi to latest to avoid version mismatch (#8781) by @sapphi-red - external.md on Windows OS (#8780) by @bddjr - align MagicString length/isEmpty with reference magic-string (#8776) by @IWANABETHATGUY ### 🚜 Refactor - extract canonical_ref_resolving_namespace helper (#8836) by @Boshen ### 📚 Documentation - improve external examples for cross-platform correctness (#8786) by @hyf0-agent - update reference to transform function in plugin API documentation (#8778) by @zOadT ### ⚡ Performance - reduce timing of `dervie_entries_aware_chunk_name` (#8847) by @AliceLanniste - bench: remove redundant sourcemap benchmark cases (#8825) by @Boshen - reduce intermediate allocations in `collapse_sourcemaps` (#8821) by @Boshen - enable parallel AST cloning on macOS (#8814) by @Boshen ### 🧪 Testing - watch: use polling watcher and retry for watch error test (#8772) by @sapphi-red ### ⚙️ Miscellaneous Tasks - justfile: skip setup-vite-plus if vp is already installed (#8862) by @Boshen - add expectWarning option to test config (#8861) by @IWANABETHATGUY - justfile: support windows for `just setup` (#8846) by @AliceLanniste - deps: update rust crates (#8852) by @renovate[bot] - deps: update endbug/version-check action to v3 (#8855) by @renovate[bot] - deps: update github-actions (#8853) by @renovate[bot] - deps: update dependency vitepress to v2.0.0-alpha.17 (#8854) by @renovate[bot] - deps: update npm packages (#8851) by @renovate[bot] - bench: use mimalloc as global allocator in bench crate (#8844) by @IWANABETHATGUY - reuse native build artifact in node-validation job (#8826) by @Boshen - speed up CodSpeed benchmark build by disabling LTO (#8824) by @Boshen - remove redundant critcmp benchmark job (#8823) by @Boshen - deps: update rust crate oxc_sourcemap to v6.1.0 (#8785) by @renovate[bot] - node: migrate oxlint and oxfmt to Vite+ (#8813) by @Boshen - revert namespace runners for release build jobs (#8820) by @Boshen - migrate runners to namespace (#8819) by @Boshen - test: relax test utils path assertion to support git worktrees (#8816) by @younggglcy - rename `examples/lazy` to `examples/lazy-compilation` (#8789) by @shulaoda - improve "needs reproduction" wording by @Boshen - deps: update dependency oxlint-tsgolint to v0.17.1 (#8807) by @renovate[bot] - enable 7 previously-skipped MagicString tests (#8771) by @IWANABETHATGUY - upgrade oxc to 0.121.0 (#8784) by @shulaoda - increase Windows dev drive size from 12GB to 20GB (#8779) by @Copilot ### ❤️ New Contributors * @elderapo made their first contribution in [#8848](#8848) * @younggglcy made their first contribution in [#8816](#8816) * @bddjr made their first contribution in [#8780](#8780) * @zOadT made their first contribution in [#8778](#8778) Co-authored-by: shulaoda <165626830+shulaoda@users.noreply.github.com>
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## [1.0.0-rc.11] - 2026-03-23 ### 🚀 Features - magicString replace with regex (#8802) by @IWANABETHATGUY - support `output.sourcemapExcludeSources` option (#8828) by @sapphi-red - support `getIndentString` in MagicString (#8775) by @IWANABETHATGUY - MagicString ignoreList support (#8773) by @IWANABETHATGUY ### 🐛 Bug Fixes - forward test filters through vp run (#8870) by @younggglcy - types: remove `pluginName` from `MinimalPluginContext` (#8864) by @sapphi-red - do not report eval?.() as direct eval (#8860) by @IWANABETHATGUY - handle negative indices, overlapping ranges, and moved content in MagicString remove (#8829) by @IWANABETHATGUY - enable arbitrary_precision for serde_json to fix JSON float parsing (#8848) by @elderapo - resolve TypeScript lint errors (#8841) by @Boshen - avoid panic on multi-byte UTF-8 chars in hash placeholder iterator (#8790) by @shulaoda - ci: skip failing vite build watch raw query test (#8840) by @Boshen - ci: use step-level env override to unset VITE_PLUS_CLI_BIN in vite tests (#8838) by @Boshen - ci: move vite tests into CI workflow by @Boshen - ci: unset all VITE_PLUS_* env vars in vite-tests workflow (#8837) by @Boshen - test: skip watch CLI tests on Windows (#8830) by @Boshen - ci: unset VITE_PLUS_CLI_BIN in vite-tests workflow (#8832) by @Boshen - remove redundant bare side-effect imports in entry/facade chunks (#8804) by @h-a-n-a - magicString prepend issues (#8797) by @IWANABETHATGUY - ci: use `vpx` instead of `vp exec` for `pkg-pr-new` (#8827) by @Boshen - set `order` for callable plugins (#8815) by @sapphi-red - handle reversed slice ranges with moved content (#8750) by @IWANABETHATGUY - update emnapi to latest to avoid version mismatch (#8781) by @sapphi-red - external.md on Windows OS (#8780) by @bddjr - align MagicString length/isEmpty with reference magic-string (#8776) by @IWANABETHATGUY ### 🚜 Refactor - extract canonical_ref_resolving_namespace helper (#8836) by @Boshen ### 📚 Documentation - improve external examples for cross-platform correctness (#8786) by @hyf0-agent - update reference to transform function in plugin API documentation (#8778) by @zOadT ### ⚡ Performance - reduce timing of `dervie_entries_aware_chunk_name` (#8847) by @AliceLanniste - bench: remove redundant sourcemap benchmark cases (#8825) by @Boshen - reduce intermediate allocations in `collapse_sourcemaps` (#8821) by @Boshen - enable parallel AST cloning on macOS (#8814) by @Boshen ### 🧪 Testing - watch: use polling watcher and retry for watch error test (#8772) by @sapphi-red ### ⚙️ Miscellaneous Tasks - deps: update dependency @oxc-project/types to v0.122.0 (#8873) by @renovate[bot] - publish-to-npm: use correct vp pm publish (#8871) by @shulaoda - justfile: skip setup-vite-plus if vp is already installed (#8862) by @Boshen - add expectWarning option to test config (#8861) by @IWANABETHATGUY - justfile: support windows for `just setup` (#8846) by @AliceLanniste - deps: update rust crates (#8852) by @renovate[bot] - deps: update endbug/version-check action to v3 (#8855) by @renovate[bot] - deps: update github-actions (#8853) by @renovate[bot] - deps: update dependency vitepress to v2.0.0-alpha.17 (#8854) by @renovate[bot] - deps: update npm packages (#8851) by @renovate[bot] - bench: use mimalloc as global allocator in bench crate (#8844) by @IWANABETHATGUY - reuse native build artifact in node-validation job (#8826) by @Boshen - speed up CodSpeed benchmark build by disabling LTO (#8824) by @Boshen - remove redundant critcmp benchmark job (#8823) by @Boshen - deps: update rust crate oxc_sourcemap to v6.1.0 (#8785) by @renovate[bot] - node: migrate oxlint and oxfmt to Vite+ (#8813) by @Boshen - revert namespace runners for release build jobs (#8820) by @Boshen - migrate runners to namespace (#8819) by @Boshen - test: relax test utils path assertion to support git worktrees (#8816) by @younggglcy - rename `examples/lazy` to `examples/lazy-compilation` (#8789) by @shulaoda - improve "needs reproduction" wording by @Boshen - deps: update dependency oxlint-tsgolint to v0.17.1 (#8807) by @renovate[bot] - enable 7 previously-skipped MagicString tests (#8771) by @IWANABETHATGUY - upgrade oxc to 0.121.0 (#8784) by @shulaoda - increase Windows dev drive size from 12GB to 20GB (#8779) by @Copilot ### ❤️ New Contributors * @younggglcy made their first contribution in [#8870](#8870) * @elderapo made their first contribution in [#8848](#8848) * @bddjr made their first contribution in [#8780](#8780) * @zOadT made their first contribution in [#8778](#8778) --------- Co-authored-by: shulaoda <165626830+shulaoda@users.noreply.github.com>
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Summary
arbitrary_precisionfeature forserde_jsoninrolldown_commonProblem
When rolldown converts a
.jsonfile to a JS module, numbers with 17 significantdigits can silently change value. For example:
114.35143799257997114.35143799257996114.35143799257997406.31486713248995406.3148671324899406.31486713248995The root cause is
serde_json's default float parser, which has off-by-oneULP (unit in the last place) errors for certain inputs. The parsed f64 differs
by 1 bit of mantissa from the correct nearest value.
Fix
Enable
serde_json'sarbitrary_precisionfeature. This changes the internalrepresentation of
serde_json::Numberfromf64to a raw string, andas_f64()then delegates to Rust's standard
str::parse::<f64>()— which uses theEisel-Lemire algorithm and is correctly rounded.
Test plan
test_float_17_significant_digitscovering the 4 values from theoriginal Vite issue
json_to_programtests passcargo checkpasses with no compilation errorsFixes: vitejs/vite#21982
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