Round debug float output to 4 decimal places by NickGerleman · Pull Request #55879 · facebook/react-native

NickGerleman · 2026-03-03T14:48:04Z

Summary:
Float values in debug layout metrics output (used by Fantom test assertions) are
subject to floating-point precision differences across platforms and compilers
(e.g., 66.6667 vs 66.66666412353516), causing flaky test comparisons.

This changes toString(const double&) in DebugStringConvertible.cpp to format
floats with 4 decimal places using snprintf("%.4f") and strip trailing zeros,
replacing double-conversion's ToShortest(). This is debug-only code (guarded
by #if RN_DEBUG_STRING_CONVERTIBLE) so the precision change is safe for all
consumers.

The double-conversion dependency is also removed from the BUCK file since it is
no longer used.

Output examples:

0.0 → "0"
100.0 → "100"
66.66666412353516 → "66.6667"
1.5 → "1.5"
33.333333 → "33.3333"

Changelog: [Internal]

Reviewed By: javache

Differential Revision: D95041966

meta-codesync · 2026-03-03T14:48:14Z

@NickGerleman has exported this pull request. If you are a Meta employee, you can view the originating Diff in D95041966.

Summary: Float values in debug layout metrics output (used by Fantom test assertions) are subject to floating-point precision differences across platforms and compilers (e.g., `66.6667` vs `66.66666412353516`), causing flaky test comparisons. This changes `toString(const double&)` in `DebugStringConvertible.cpp` to format floats with 4 decimal places using `snprintf("%.4f")` and strip trailing zeros, replacing `double-conversion`'s `ToShortest()`. This is debug-only code (guarded by `#if RN_DEBUG_STRING_CONVERTIBLE`) so the precision change is safe for all consumers. The `double-conversion` dependency is also removed from the BUCK file since it is no longer used. Output examples: - `0.0` → `"0"` - `100.0` → `"100"` - `66.66666412353516` → `"66.6667"` - `1.5` → `"1.5"` - `33.333333` → `"33.3333"` Changelog: [Internal] Reviewed By: javache Differential Revision: D95041966

Summary: Pull Request resolved: facebook#55879 Float values in debug layout metrics output (used by Fantom test assertions) are subject to floating-point precision differences across platforms and compilers (e.g., `66.6667` vs `66.66666412353516`), causing flaky test comparisons. This changes `toString(const double&)` in `DebugStringConvertible.cpp` to format floats with 4 decimal places using `snprintf("%.4f")` and strip trailing zeros, replacing `double-conversion`'s `ToShortest()`. This is debug-only code (guarded by `#if RN_DEBUG_STRING_CONVERTIBLE`) so the precision change is safe for all consumers. The `double-conversion` dependency is also removed from the BUCK file since it is no longer used. Output examples: - `0.0` → `"0"` - `100.0` → `"100"` - `66.66666412353516` → `"66.6667"` - `1.5` → `"1.5"` - `33.333333` → `"33.3333"` Changelog: [Internal] Reviewed By: javache Differential Revision: D95041966

Summary: Float values in debug layout metrics output (used by Fantom test assertions) are subject to floating-point precision differences across platforms and compilers (e.g., `66.6667` vs `66.66666412353516`), causing flaky test comparisons. This changes `toString(const double&)` in `DebugStringConvertible.cpp` to format floats with 4 decimal places using `snprintf("%.4f")` and strip trailing zeros, replacing `double-conversion`'s `ToShortest()`. This is debug-only code (guarded by `#if RN_DEBUG_STRING_CONVERTIBLE`) so the precision change is safe for all consumers. The `double-conversion` dependency is also removed from the BUCK file since it is no longer used. Output examples: - `0.0` → `"0"` - `100.0` → `"100"` - `66.66666412353516` → `"66.6667"` - `1.5` → `"1.5"` - `33.333333` → `"33.3333"` Changelog: [Internal] Reviewed By: javache Differential Revision: D95041966

Summary: Pull Request resolved: facebook#55879 Float values in debug layout metrics output (used by Fantom test assertions) are subject to floating-point precision differences across platforms and compilers (e.g., `66.6667` vs `66.66666412353516`), causing flaky test comparisons. This changes `toString(const double&)` in `DebugStringConvertible.cpp` to format floats with 4 decimal places using `snprintf("%.4f")` and strip trailing zeros, replacing `double-conversion`'s `ToShortest()`. This is debug-only code (guarded by `#if RN_DEBUG_STRING_CONVERTIBLE`) so the precision change is safe for all consumers. The `double-conversion` dependency is also removed from the BUCK file since it is no longer used. Output examples: - `0.0` → `"0"` - `100.0` → `"100"` - `66.66666412353516` → `"66.6667"` - `1.5` → `"1.5"` - `33.333333` → `"33.3333"` Changelog: [Internal] Reviewed By: javache Differential Revision: D95041966

Summary: Float values in debug layout metrics output (used by Fantom test assertions) are subject to floating-point precision differences across platforms and compilers (e.g., `66.6667` vs `66.66666412353516`), causing flaky test comparisons. This changes `toString(const double&)` in `DebugStringConvertible.cpp` to format floats with 4 decimal places using `snprintf("%.4f")` and strip trailing zeros, replacing `double-conversion`'s `ToShortest()`. This is debug-only code (guarded by `#if RN_DEBUG_STRING_CONVERTIBLE`) so the precision change is safe for all consumers. The `double-conversion` dependency is also removed from the BUCK file since it is no longer used. Output examples: - `0.0` → `"0"` - `100.0` → `"100"` - `66.66666412353516` → `"66.6667"` - `1.5` → `"1.5"` - `33.333333` → `"33.3333"` Changelog: [Internal] Reviewed By: javache Differential Revision: D95041966

Summary: Pull Request resolved: facebook#55879 Float values in debug layout metrics output (used by Fantom test assertions) are subject to floating-point precision differences across platforms and compilers (e.g., `66.6667` vs `66.66666412353516`), causing flaky test comparisons. This changes `toString(const double&)` in `DebugStringConvertible.cpp` to format floats with 4 decimal places using `snprintf("%.4f")` and strip trailing zeros, replacing `double-conversion`'s `ToShortest()`. This is debug-only code (guarded by `#if RN_DEBUG_STRING_CONVERTIBLE`) so the precision change is safe for all consumers. The `double-conversion` dependency is also removed from the BUCK file since it is no longer used. Output examples: - `0.0` → `"0"` - `100.0` → `"100"` - `66.66666412353516` → `"66.6667"` - `1.5` → `"1.5"` - `33.333333` → `"33.3333"` Changelog: [Internal] Reviewed By: javache Differential Revision: D95041966

Summary: Float values in debug layout metrics output (used by Fantom test assertions) are subject to floating-point precision differences across platforms and compilers (e.g., `66.6667` vs `66.66666412353516`), causing flaky test comparisons. This changes `toString(const double&)` in `DebugStringConvertible.cpp` to format floats with 4 decimal places using `snprintf("%.4f")` and strip trailing zeros, replacing `double-conversion`'s `ToShortest()`. This is debug-only code (guarded by `#if RN_DEBUG_STRING_CONVERTIBLE`) so the precision change is safe for all consumers. The `double-conversion` dependency is also removed from the BUCK file since it is no longer used. Output examples: - `0.0` → `"0"` - `100.0` → `"100"` - `66.66666412353516` → `"66.6667"` - `1.5` → `"1.5"` - `33.333333` → `"33.3333"` Changelog: [Internal] Reviewed By: javache Differential Revision: D95041966

react-native-bot · 2026-03-06T09:34:12Z

This pull request was successfully merged by @NickGerleman in 3483dfa

^{When will my fix make it into a release? | How to file a pick request?}

meta-codesync · 2026-03-06T09:34:15Z

This pull request has been merged in 3483dfa.

meta-cla bot added the CLA Signed This label is managed by the Facebook bot. Authors need to sign the CLA before a PR can be reviewed. label Mar 3, 2026

meta-codesync bot added fb-exported meta-exported labels Mar 3, 2026

facebook-github-bot added p: Facebook Partner: Facebook Partner labels Mar 3, 2026

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meta-codesync bot closed this in 3483dfa Mar 6, 2026

react-native-bot added the Merged This PR has been merged. label Mar 6, 2026

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Round debug float output to 4 decimal places#55879

Round debug float output to 4 decimal places#55879
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