prefer-object-spread rule should not report Object.assign({}, ...array)

[ehmicky]

Tell us about your environment

• ESLint Version: 5.0.0-alpha.3
• Node Version: 10.1.0
• npm Version: 5.6.0

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

Please show your full configuration:

Configuration

root: true
parserOptions:
  ecmaVersion: 2018
  sourceType: script
rules:
  prefer-object-spread: 2

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 objects = array.map(mapObject)
const var = Object.assign({}, ...objects)

eslint .

What did you expect to happen?
Object.assign() should not be reported as wrong. There is no way to use object spreads in this example because objects is an array of objects. It is not possible to use object spreads to concatenate an array of objects (e.g. [{ ... }, { ... }]) into a single object.

The prefer-object-spread rule should not report a linting error when one of the arguments to Object.assign() uses an array spread.

This also means the above line with --fix would be converted to { ...objects } which is incorrect.

What actually happened? Please include the actual, raw output from ESLint.
Object.assign() was reported as wrong.

[not-an-aardvark]

Thanks for the report, I can reproduce this issue. I agree that the rule shouldn't report this case.

[platinumazure]

Question: Should the rule report for a case where the spread argument is later on? (e.g., Object.assign({}, foo, ...others))

[ljharb]

Indeed, argument spreading anywhere in the assign call requires using Object.assign, and this shouldn’t report.

However, yes, i think it should, if possible, force the latter example to Object.assign({ ...foo }, ...others)