New Rule: `no-useless-override`

Rule details

same as no-useless-constructor but with overridden methods

Related ECMAScript feature

how new? es6 classes?

What type of rule is this?

Warns about a potential problem

Example code

// fail
class Foo {
    bar() {}
}

class Bar extends Foo {
    bar() {
        super.bar()
    }
}


// pass
class Foo {
    bar() {}
}

class Bar extends Foo {
    bar() {
        console.log("doing something else")
        super.bar()
    }
}

Why should this rule be in the core instead of a plugin?

because no-useless-constructor is already a core rule and i see no reason why it shouldn’t also check for useless method overrides

Participation

• I am willing to submit a pull request to implement this rule.

Additional comments

originally raised here https://github.com/typescript-eslint/typescript-eslint/issues/4747

[mdjermanovic]

class Foo {
    bar = () => {}
}

class Bar extends Foo {
    bar = () => {
        super.bar()
    }
}

This code actually has a bug - if you call (new Bar()).bar() it will throw an error because there is no super.bar. Arrow function instance fields are not methods.

[mdjermanovic]

bar = () => { super.bar() } does not have to be useless. Consider the following example:

class A {
    x = 5;
    bar() {
        console.log(this.x);
    }
}

class B extends A {
    bar = () => {
        super.bar()
    }
}

class C extends A {
}

(0, new B().bar)(); // logs 5
(0, new C().bar)(); // throws TypeError: Cannot read property 'x' of undefined