noDuplicateEnumValues

JavaScript (and super languages)

Summary

Rule available since: v2.3.12
Diagnostic Category: lint/suspicious/noDuplicateEnumValues
This rule is recommended, meaning it is enabled by default.
This rule doesn’t have a fix.
The default severity of this rule is warning.
Sources:
- Same as @typescript-eslint/no-duplicate-enum-values

How to configure

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{
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  "linter": {
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    "rules": {
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      "suspicious": {
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        "noDuplicateEnumValues": "error"
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      }
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    }
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  }
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}

Description

Disallow duplicate enum member values.

Although TypeScript supports duplicate enum member values, people usually expect members to have unique values within the same enum. Duplicate values can lead to bugs that are hard to track down.

Examples

Invalid

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enum E {
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  A = 0,
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  B = 0,
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}

code-block.ts:3:3 lint/suspicious/noDuplicateEnumValues ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ⚠ Duplicate enum member value.
  
    1 │ enum E {
    2 │   A = 0,
  > 3 │   B = 0,
      │   ^^^^^
    4 │ }
    5 │ 
  
  ℹ Expected members to have unique values. Duplicate values can lead to bugs that are hard to track down.

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enum E {
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  A = "A",
3
  B = 'A',
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  C = `A`,
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}

code-block.ts:3:3 lint/suspicious/noDuplicateEnumValues ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ⚠ Duplicate enum member value.
  
    1 │ enum E {
    2 │   A = “A”,
  > 3 │   B = ‘A’,
      │   ^^^^^^^
    4 │   C = `A`,
    5 │ }
  
  ℹ Another duplicate enum member value.
  
    2 │   A = “A”,
    3 │   B = ‘A’,
  > 4 │   C = `A`,
      │   ^^^^^^^
    5 │ }
    6 │ 
  
  ℹ Expected members to have unique values. Duplicate values can lead to bugs that are hard to track down.

Valid

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enum E {
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  A = 0,
3
  B = 1,
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}

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enum E {
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  A = "A",
3
  B = 'B',
4
  C = `C`,
5
}