Zero width chars not showing in diff · jestjs/jest#10584

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:rocket: Feature RequestHelp WantedPinned

描述

🐛 Bug Report

Differences in strings containing zero width chars are not highlighted, making them incredibly hard to spot and debug. Eg, one of the following strings has as its first character (character at position 0) a byte order mark character as its first character, and the other has the letter "T" as its first character.

Additional useful info

UTF-16 spec on Byte Order Mark character (scroll to end of page). Its hex code is FEFF, or 65279 in decimal.
Related issues: #8448, #6881

To Reproduce

Just create two strings that look identical, one of which contains a character such as the BOM character.

Expected behavior

A clear indication of the difference.

envinfo

  System:
    OS: Linux 5.4 Ubuntu 18.04.5 LTS (Bionic Beaver)
    CPU: (8) x64 Intel(R) Core(TM) i5-8250U CPU @ 1.60GHz
  Binaries:
    Node: 14.4.0 - ~/.nvm/versions/node/v14.4.0/bin/node
    Yarn: 1.21.1 - /usr/bin/yarn
    npm: 6.14.5 - ~/.nvm/versions/node/v14.4.0/bin/npm
  npmPackages:
    jest: ^26.0.1 => 26.0.1

貢獻者指南

技術棧: typescriptnodejsjavascript
領域: testingdeveloper experience
議題類型: bug
難度: 3
預計時間: 1-3 hours
活動狀態: stale
清晰度: clear
前置要求: basic understanding of unicode charactersfamiliarity with Jest's diff logic
新手友善度: 65
研究方向: Review the issue comments (12 total) and related issues #8448 and #6881 for discussion. The fix likely involves modifying the diff algorithm in `packages/expect utils/src/utils.ts` or similar to highlight zero width characters. Explore how the current diff handles invisible characters and consider using Unicode property escapes or character width detection. Look for any existing PRs or branches that attempt a fix.