chakra-core/ChakraCore

[RegExp] Exceptions for RegExp in Annex B of the ES2017 spec shouldn't be applied when the "unicode" flag is present

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#518 opened on Mar 10, 2016

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BugSeverity: 2help wanted

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Description

Annex B.1.4 contains exceptions that allow web browsers to diverge from the normal RegExp grammar. These exceptions aren't allowed when the "unicode" flag is present, but our current implementation doesn't take this into account.

There are many exceptions, but a few examples would be:

  • PatternCharacter: {
  • CharacterClassEscape: [\d-a]
  • DecimalEscape: \3 when the number of capturing parentheses is less than 3
  • IdentityEscape: \h, \u
  • QuantifiableAssertion Quantifier: (?!.)+

The above should throw a SyntaxError when used as, e.g.,/{/u

Contributor guide

Research direction
Check how the unicode flag is detected in the RegExp parsing code, then ensure that Annex B.1.4 exceptions are skipped when that flag is set. Look at the areas where PatternCharacter, CharacterClassEscape, DecimalEscape, IdentityEscape, and QuantifiableAssertion Quantifier are parsed and add conditional checks for the unicode flag.
Tech stack
javascript
Domain
backend
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
Half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Mostly clear
Prerequisites
JavaScriptRegExp
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
30