prefer-destructuring false-positive if already declared in upper scope

Tell us about your environment

• ESLint Version: 4.13.1
• Node Version: 8.9.1
• npm Version: 5.6.0

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

Please show your full configuration:

airbnb-styleguide

What did you do? Please include the actual source code causing the issue, as well as the command that you used to run ESLint.

const foo = { bar: 1 };
let bar;

try {
  // throws an error here
  bar = foo.bar
} catch(e) {
}

// rule setting, as of the airbnb styleguide
'prefer-destructuring': ['error', {
  VariableDeclarator: {
    array: false,
    object: true,
  },
  AssignmentExpression: {
    array: true,
    object: true,
  },
}, {
  enforceForRenamedProperties: false,
}],

What did you expect to happen? I expect that the destructing error won’t show up. As the variable bar is already declared in an upper scope not in the same.

What actually happened? Please include the actual, raw output from ESLint. The rule suggested to prefer destructing although it won’t work with destructing here, as I have to declare a new variable.

[platinumazure]

You can destructure without a declaration:

const foo = { bar: 1 };
let bar;

try {
  // throws an error here
  ({ bar } = foo)
} catch(e) {
}

Unfortunately, you need parentheses for object destructuring due to the language grammar, but otherwise destructuring does work without a declaration.

[mrchief]

I also want to point out that I’m aware of AssignmentExpression and VariableDeclarator options. What I meant with “another option” is something like this:

should not warn for cases like these

let fields = []

if(someCondition) {
  fields = grabFromSomewhere(...)
} else {
  fields = grabbedFromSomewhereElse.fields
}

should warn for cases like these

let fields = []

if(someCondition) {
  fields = grabbedFromSomewhereElse.fields
}

because above can be potentially refactored to use destructuring.

Not a great example but I hope you understand. And probably I’m asking for a lot! 😃