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noEmptyInterface

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Diagnostic Category: lint/suspicious/noEmptyInterface

Since: v1.0.0

Sources:

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.

The rule ignores empty interfaces that extends one or multiple types.

Examples

Section titled Examples

Invalid

Section titled Invalid
interface A {}
code-block.ts:1:1 lint/suspicious/noEmptyInterface  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

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

Valid

Section titled Valid
interface A {
  prop: string;
}


// Allow empty interfaces that extend a type.
interface B extends A {}


// Allow empty interfaces in ambient modules
declare module "mod" {
  interface C {}
}
Section titled Related links