no-sequences rule in arrow function body returning object is not aplicable

In short: It is not possible to apply no-sequences rule in return part of arrow function in form <argumentList> => <expression> where <expression> is <objectLiteral> because this object literal must be enclosed in parentheses.

Example: I have this bad piece of code and want no-sequences rule to warn me about:

export default injectIntl(connect(state => ({
  auth: state.auth,
}, { // <-- BAD
  login,
}))(LoginForm));

no-sequences rule is not designed for this situation. Correct code should be:

export default injectIntl(connect(state => ({
  auth: state.auth,
}), {
  login,
})(LoginForm));

Sadly, both samples executes and both without lint warnings. Rule no-sequences is not applied if comma expression is explicitly enclosed in parentheses. But it is also impossible to write arrow function returning object without enclosing it into parenthese so no-sequences rule is not usable in this case.

Proposed Solution

If there is arrow (e.g. (arg) => ({result: arg})), no-sequences rule can be enabled in result expression (this is {result: arg} inside parentheses) So it can report if it spot (arg) => ({result: arg}, {foo: 123})

The rule is not fired because of this on line 95 of the no-sequences rule:

if (isParenthesised(node)) {
    return;
}

Should be changed to something similar to:

if (isParenthesised(node) && !isArrowFunctionReturnExpression(node)) {
    return;
}

Thanks to @pedrottimark and @vitorbal for help on Gitter.

[langpavel]

You are blazingly fast! Thanks!

[mysticatea]

Thank you for this issue.

I confirmed it on the online demo.

I’ll fix it.