Ban redundant IIFEs

Please describe what the rule should do:

Often people converting legacy script style JS into modules keep redundant IIFEs. Write a rule to ban these.

A redundant IIFE is an IIFE where the result is not used, or the result is statically analysable.

What category of rule is this? (place an “X” next to just one item)

[ ] Enforces code style [ ] Warns about a potential error [ ] Suggests an alternate way of doing something X [ ] Other (please specify:)

Provide 2-3 code examples that this rule will warn about:

// bad
((global) => {
    const foo = 3;
    ham();
    return 7;
})(window);

// good
const window = global;
const foo = 3;
ham();

// bad
$(((global) => {
    const foo = 3;
    ham();
    return 7;
})(window));

// 'good'

const window = global;
const foo = 3;
ham();
$(7);

// bad
const res = ((global) => {
    const foo = 3;
    ham();
    return 7;
})(window);

// 'good'
const window = global;
const foo = 3;
ham();
const res = 7;

// good
const res = (() => {
    switch (foo) {
        case 'ham': return 'spam';
        case 'eggs': return 'bacon';
        default: return 'sauce';
    }
})();

// bad
const res = (() => {
    switch (foo) {
        case 'ham': return 'sauce';
        case 'eggs': return 'sauce';
        default: return 'sauce';
    }
})();

// good
const res = 'sauce';

// bad
const res = (() => {
    switch (foo) {
        case 'ham': return 'sauce';
        case 'eggs': return 'sauce';
        default: throw new Error('invalid breakfast item');
    }
})();

// good
const res = 'sauce';
switch(foo) {
    case 'ham': break;
    case 'eggs': break;
    default: throw new Error('invalid breakfast item');
}

Why should this rule be included in ESLint (instead of a plugin)? Seems pretty handy, doesn’t depend on exotic syntax.

[not-an-aardvark]

I see, thanks for explaining.

Hmm, personally I’m not convinced that this rule is worth adding to core – it seems like a very user-specific preference. However, let’s see what the rest of the team thinks.

[not-an-aardvark]

It seems like the team is not in favor of this rule, so I’m going to close this issue. However, you can always implement the rule as part of a plugin.