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noMisleadingCharacterClass

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Diagnostic Category: lint/suspicious/noMisleadingCharacterClass

Since: v1.5.0

Sources:

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 expressions which include multiple code point characters in character class syntax.

Examples

Section titled Examples

Invalid

Section titled Invalid
/^[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.
  
/^[❇️]$/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.
  
/^[👶🏻]$/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.
  
/^[🇯🇵]$/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.
  
/^[👨‍👩‍👦]$/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.
  
/^[👍]$/; // 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

Section titled Valid
/^[abc]$/;
/^[👍]$/u;
/^[\q{👶🏻}]$/v;
Section titled Related links