Rule proposal: `simple-condition-first`

[fisker]

Description

When writing multiple conditions, the simple one should come first.

I believe this can improve performance. The direct boolean check and variable ===/!== comparison are obviously cheaper.

Examples

// ❌
if (check(foo) && bar);

// ✅
if (bar && check(foo));

// ❌
if (foo.bar.baz === 1 && bar === 2);

// ✅
if (bar === 2 && foo.bar.baz === 1);

Proposed rule name

simple-condition-first

Additional Info

There is an internal rule in Prettier codebase checking a particular case https://github.com/prettier/prettier/blob/46061a160f7a6726d11d047647d59036435a3279/scripts/tools/eslint-plugin-prettier-internal-rules/test.js#L39-L44 , but it will be great to have a generic rule.

[sindresorhus]

Sounds useful. I think the name should be prefer-simple-condition-first.

[axetroy]

Due to the change of position, it may affect the logic of the original code.

[fisker]

Example?

[axetroy]

Example?

Perhaps I'm being too nitpicky.

If there are side effects, the results may be quite different.

These changes in conditions must require that the function be pure and immutable.

Side Effect

let bar = false;

function check(foo) {
  bar = true;
  return true;
}

- check(foo) && bar // true
+ bar && check(foo) // false

Mutable

const arr = [1, 2, 3];
const bar = false;

if (arr.pop() && bar) {
  // ...
}

if (bar && arr.pop()) {
  // ...
}