New option in no-unsafe-negation to report ! a < b

[mdjermanovic]

What rule do you want to change?

no-unsafe-negation

This rule disallows negating the left operand of Relational Operators.

The rule currently targets only in and instanceof.

<, >, <=, >= are also relational operators.

! a < b is equivalent to (a ? 0 : 1) < b (I think), which is rarely the intended meaning:

function min(a, b) {
    let m = a;
    if (! a < b) {
        m = b;
    }
    return m;
}

min(1, 2); // 2

Does this change cause the rule to produce more or fewer warnings?

More if the option is set to true. Default is false.

How will the change be implemented? (New option, new default behavior, etc.)?

New option.

Please provide some example code that this change will affect:

/*eslint no-unsafe-negation: "error"*/

if (! a < b) {}

while (! a > b) {}

foo = ! a <= b;

foo = ! a >= b;

What does the rule currently do for this code?

Nothing.

What will the rule do after it's changed?

4 errors

/*eslint no-unsafe-negation: ["error", { "enforceForOrderingRelations": true }]*/

if (! a < b) {} // error

while (! a > b) {} // error

foo = ! a <= b; // error

foo = ! a >= b; // error

Are you willing to submit a pull request to implement this change?

Yes.

[kaicataldo]

This has now been accepted.

[samrae7]

@mdjermanovic do you still want to do the PR for this? If not I could take it on

[mdjermanovic]

@samrae7 feel free to claim this. PR is welcome, thanks!

[samrae7]

@mdjermanovic thank you. I will work on it over the weekend