perf(json): avoid first-char regex for direct JSON bodies#744
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Phillip9587 wants to merge 1 commit into
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perf(json): avoid first-char regex for direct JSON bodies#744Phillip9587 wants to merge 1 commit into
Phillip9587 wants to merge 1 commit into
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Skip the RFC 7159 whitespace scan when strict JSON bodies start directly with `{` or `[`. This avoids regex execution on the common valid path while preserving strict-mode handling for leading whitespace and primitive values.
Update the first non-whitespace regex to match end-of-string so whitespace-only bodies return `undefined` without relying on a failed match/backtracking path.
UlisesGascon
approved these changes
Jul 7, 2026
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Could you tell us how much of an improvement there is? |
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Author
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Micro Benchmark shows:
The load test from perf-wg do not show a big difference because http-handling, streaming and json parsing take much longer. |
bjohansebas
reviewed
Jul 9, 2026
| * %x0D ) ; Carriage return | ||
| */ | ||
| const FIRST_CHAR_REGEXP = /^[\x20\x09\x0a\x0d]*([^\x20\x09\x0a\x0d])/ // eslint-disable-line no-control-regex | ||
| const FIRST_NON_WHITESPACE_REGEXP = /^[\x20\x09\x0a\x0d]*([^\x20\x09\x0a\x0d]|$)/ // eslint-disable-line no-control-regex |
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Okay, for future reviewers, here's the regex change.
" {json}"
master=match[1]="{"
PR=match[1]="{"
"123" (primitivo)
master=match[1]="1"
PR=match[1]="1"
" " (solo whitespace)
master=NULL (no match)
PR=match[1]=""
"" (vacio)
master=NULL (no match)
PR=match[1]=""
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Skip the RFC 7159 whitespace scan when strict JSON bodies start directly with
{or[. This avoids regex execution on the common valid path while preserving strict-mode handling for leading whitespace and primitive values.Updated the first non-whitespace regex to match end-of-string so whitespace-only bodies return
undefinedwithout relying on a failed match/backtracking path.