noMisleadingCharacterClass

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JavaScript (and super languages)

Summary

Rule available since: v1.5.0
Diagnostic Category: lint/suspicious/noMisleadingCharacterClass
This rule is recommended, which means is enabled by default.
This rule has a safe fix.
The default severity of this rule is error.
Sources:
- Same as no-misleading-character-class

Description

Disallow characters made with multiple code points in character class syntax.

Unicode includes the characters which are made with multiple code points. e.g. Á, 🇯🇵, 👨‍👩‍👦. A RegExp character class /[abc]/ cannot handle characters with multiple code points. For example, the character ❇️ consists of two code points: ❇ (U+2747) and VARIATION SELECTOR-16 (U+FE0F). If this character is in a RegExp character class, it will match to either ❇ or VARIATION SELECTOR-16 rather than ❇️. This rule reports the regular expression literals which include multiple code point characters in character class syntax.

Examples

Invalid

1
/^[Á]$/u;

code-block.js:1:4 lint/suspicious/noMisleadingCharacterClass ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ A character class cannot match a character and a combining character.
  
  > 1 │ /^[Á]$/u;
      │    ^
    2 │ 
  
  ℹ A character and a combining character forms a new character. Replace the character class with an alternation.

1
/^[❇️]$/u;

code-block.js:1:4 lint/suspicious/noMisleadingCharacterClass ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ A character class cannot match a character and a combining character.
  
  > 1 │ /^[❇️]$/u;
      │    ^
    2 │ 
  
  ℹ A character and a combining character forms a new character. Replace the character class with an alternation.

1
/^[👶🏻]$/u;

code-block.js:1:4 lint/suspicious/noMisleadingCharacterClass ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ A character class cannot match an emoji with a skin tone modifier.
  
  > 1 │ /^[👶🏻]$/u;
      │    ^^^^
    2 │ 
  
  ℹ Replace the character class with an alternation.

1
/^[🇯🇵]$/u;

code-block.js:1:4 lint/suspicious/noMisleadingCharacterClass ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ A character class cannot match a pair of regional indicator symbols.
  
  > 1 │ /^[🇯🇵]$/u;
      │    ^^
    2 │ 
  
  ℹ A pair of regional indicator symbols encodes a country code. Replace the character class with an alternation.

1
/^[👨‍👩‍👦]$/u;

code-block.js:1:4 lint/suspicious/noMisleadingCharacterClass ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ A character class cannot match a joined character sequence.
  
  > 1 │ /^[👨‍👩‍👦]$/u;
      │    ^^^^
    2 │ 
  
  ℹ A zero width joiner composes several emojis into a new one. Replace the character class with an alternation.

1
/^[👍]$/; // surrogate pair without u flag

code-block.js:1:4 lint/suspicious/noMisleadingCharacterClass  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ A character class cannot match a surrogate pair. Add the ‘u’ unicode flag to match against them.
  
  > 1 │ /^[👍]$/; // surrogate pair without u flag
      │    ^^
    2 │ 
  
  ℹ A surrogate pair forms a single codepoint, but is encoded as a pair of two characters. Without the unicode flag, the regex matches a single surrogate character.
  
  ℹ Safe fix: Add unicode u flag to regex
  
    1 │ /^[👍]$/u;·//·surrogate·pair·without·u·flag
      │         +

Valid

1
/^[abc]$/;
2
/^[👍]$/u;
3
/^[\q{👶🏻}]$/v;

How to configure

1
{
2
  "linter": {
3
    "rules": {
4
      "suspicious": {
5
        "noMisleadingCharacterClass": "error"
6
      }
7
    }
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  }
9
}