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Lint Rules

noEmptyInterface (since v11.0.0)

Disallow the declaration of empty interfaces.

An empty interface in TypeScript does very little: any non-nullable value is assignable to {}. Using an empty interface is often a sign of programmer error, such as misunderstanding the concept of {} or forgetting to fill in fields.

Source: https://typescript-eslint.io/rules/no-empty-interface

Examples

Invalid

interface A {}
nursery/noEmptyInterface.js:1:1 lint/nursery/noEmptyInterface  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ An empty interface is equivalent to '{}'.
  
  > 1 │ interface A {}
      │ ^^^^^^^^^^^^^^
    2 │ 
  
  ℹ Safe fix: Convert empty interface to type alias.
  
    1   │ - interface·A·{}
      1 │ + type·A·=·{}
    2 2 │   
  

// A === B
interface A extends B {}
nursery/noEmptyInterface.js:2:1 lint/nursery/noEmptyInterface  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ An interface declaring no members is equivalent to its supertype.
  
    1 │ // A === B
  > 2 │ interface A extends B {}
      │ ^^^^^^^^^^^^^^^^^^^^^^^^
    3 │ 
  
  ℹ Safe fix: Convert empty interface to type alias.
  
    1 1 │   // A === B
    2   │ - interface·A·extends·B·{}
      2 │ + type·A·=·B
    3 3 │

Valid

interface A {
  prop: string;
}

// The interface can be used as an union type.
interface A extends B, C {}