prefer-destructuring should not check non-numeric indexes

Tell us about your environment

• ESLint Version: 4.14.0
• Node Version: 9.3.9
• npm Version: 5.6.0

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

Please show your full configuration:

Configuration

{
  "parserOptions": {
    "ecmaVersion": 6,
    "sourceType": "module"
  },

  "extends": [
    "airbnb-base"
  ],

  "rules": {
    "class-methods-use-this": "off",
    "import/no-extraneous-dependencies": ["off", {"devDependencies": ["webpack-config/*.js"]}],
    "no-prototype-builtins": "off",
    "no-param-reassign": [0],
    "prefer-default-export": "off"
  }
}

What rule do you want to change? prefer-destructuring

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

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

Please provide some example code that this change will affect:

const INTEGER_WORDS = {
  one: 1,
  two: 2,
  three: 3,
  four: 4,
 };

let num = 1;
num = INTEGER_WORDS[num]; 

What does the rule currently do for this code?

Generates a warning for num = INTEGER_WORDS[num];

What will the rule do after it’s changed?

It will ignore array indexes/keys that are not constants. I would argue this should always be the case, as it must be considered bad practice to destructure from a computed index or key.

[j-f1]

You could do let { [num]: num } = INTEGER_WORDS, but I agree that that should be an exception.

[aparajita]

The fix seems to be quite easy. I haven’t thought through it deeply, but this works:

Change these lines to:

if (!rightNode.computed && ((property.type === "Literal" && leftNode.name === property.value) ||
    (property.type === "Identifier" && leftNode.name === property.name))) {

I added the check for rightNode.computed. If that’s true, a non-literal expression is being used.