no-empty-interface.md

Disallow the declaration of empty interfaces (no-empty-interface)

An empty interface is equivalent to its supertype. If the interface does not implement a supertype, then the interface is equivalent to an empty object ({}). In both cases it can be omitted.

Rule Details

This rule aims to ensure that only meaningful interfaces are declared in the code.

The following patterns are considered warnings:

// an empty interface
interface Foo {}

// an interface with only one supertype (Bar === Foo)
interface Bar extends Foo {}

// an interface with an empty list of supertypes
interface Baz {}

The following patterns are not warnings:

// an interface with any number of members
interface Foo {
    name: string;
}

// same as above
interface Bar {
    age: number;
}

// an interface with more than one supertype
// in this case the interface can be used as a replacement of a union type.
interface Baz extends Foo, Bar {}

When Not To Use It

If you don't care about having empty/meaningless interfaces, then you will not need this rule.

Compatibility

• TSLint: no-empty-interface