Microsoft/monaco-editor

TS regex missed by Monarch grammar

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#2,512 opened on Jun 2, 2021

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Description

Extracted from https://github.com/microsoft/TypeScript-Website/issues/1870

const x = true ? /^([^"]*)"/ : /^([^']*)'/

/^([^"]*)"/ is not identified as a regex by the TS Monarch grammar, which breaks bracket matching:

image

Contributor guide

Tech stack
typescript
Domain
developer experience
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.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
Understanding of Monarch tokenizerFamiliarity with TypeScript syntaxBasic regex knowledge
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
60
Research direction
The bug occurs in the TypeScript Monarch grammar at line 76 of typescript.ts (https://github.com/microsoft/monaco languages/blob/319a1ddf568438d59a3851784b092cdf1f88e29e/src/typescript/typescript.ts). The regex pattern after a ternary operator is not being tokenized as a regex. To fix, examine the tokenizer rules for handling '/' after conditional expressions and ensure regex detection works for patterns like `/^([^"]*)"/` and `/^([^']*)'/`. Consider adding a state or rule to differentiate division from regex in such contexts.