Microsoft/monaco-editor

F# highlighting issues with block comments tokenized by strings

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#1240 opened on Dec 18, 2018

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Description

monaco-editor version: 0.15.6 Browser: Edge OS: Windows NT x64 10.0.17763 Note: Issue also affects VS Code

Steps reproducing the issue: F# tokenizes strings in block comments. Basically, Monaco is breaking the highlighting of code that uses strings within block comments. Here are some images:

This image is from The F# 4.1 Language Specification manual (section 3.2, pg. 23). Imgur

This is how Visual Studio IDE correctly interprets the styling: Imgur

This is how Monaco interpret the styling: Imgur

Comments used to test the highlighter:

(* Here's a code snippet: let s = "*)" *) let i = 1
(* """ *) let j = 2

Contributor guide

Tech stack
typescript
Domain
frontenddeveloper 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.
blocked
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
TextMate grammarF# syntaxMonaco editor codebase
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
20
Research direction
The issue is a bug in the F# syntax highlighting where strings inside block comments are incorrectly tokenized. The fix involves modifying the TextMate grammar for F# in the Monaco editor source (likely 'src/fsharp.ts' or similar). First, examine the existing grammar patterns to understand how block comments and strings are defined. Then, adjust the patterns to ensure that strings do not get tokenized when they appear inside block comments, as per the F# specification. Test with the provided examples: '(* Here's a code snippet: let s = "*)" *) let i = 1' and '(* """ *) let j = 2'. Check if the issue has been resolved in later versions or if there is an existing pull request.