"no-mixed-operators" always outputs errors in pairs of two

[feross]

Tell us about your environment

• ESLint Version: 3.15.0
• Node Version: 7.5.0
• npm Version: 4.1.2

What parser (default, Babel-ESLint, etc.) are you using? default

Please show your full configuration:

    "no-mixed-operators": ["error", {
        "groups": [
            ["+", "-", "*", "/", "%", "**"],
            ["==", "!=", "===", "!==", ">", ">=", "<", "<="],
            ["&&", "||"],
            ["in", "instanceof"]
        ],
        "allowSamePrecedence": true
    }],

What did you do? Please include the actual source code causing the issue.

var eLen = nBytes * 8 - mLen - 1

What did you expect to happen?

One error about mixed operators.

What actually happened? Please include the actual, raw output from ESLint.

Two errors about mixed operators, one for each operator:

  index.js:3:21: Unexpected mix of '*' and '-'. (no-mixed-operators)
  index.js:3:25: Unexpected mix of '*' and '-'. (no-mixed-operators)

Is this expected behavior? It seems there is no case where this rule emits a single error, since by definition "mixing" operators requires 2 operators. It would be more intuitive to me if a single error was emitted.

[not-an-aardvark]

This seems like a bug. Thanks for the report!

[mysticatea]

Actually, this is intentional.

Unexpected mix of '*' and '-'., in this case, it shows 2 warnings at the * and - to make clear what operators are mixed.

[feross]

@mysticatea Wouldn't showing a single warning at the first operator suffice?

[mysticatea]

I will not oppose it. However, this rule warns consecutive 2 operators on AST, so it might be at far locations on source code text if the expression is complex. It was the reason that I made 2 warnings.

[feross]

Makes sense. Either way is fine, though I was initially confused by the double error.

[nzakas]

I think this is the correct behavior as well. Perhaps we should update the docs to mention this?