eslint/no-unsafe-optional-chaining Correctness

What it does

Disallow use of optional chaining in contexts where the undefined value is not allowed

Why is this bad?

The optional chaining (?.) expression can short-circuit with a return value of undefined. Therefore, treating an evaluated optional chaining expression as a function, object, number, etc., can cause TypeError or unexpected results. For example:

Examples

Examples of incorrect code for this rule:

var obj = undefined;
1 in obj?.foo; // TypeError
with (obj?.foo); // TypeError
for (bar of obj?.foo); // TypeError
bar instanceof obj?.foo; // TypeError
const { bar } = obj?.foo; // TypeError

Configuration

This rule accepts a configuration object with the following properties:

disallowArithmeticOperators

type: boolean

default: false

Disallow arithmetic operations on optional chaining expressions. If this is true, this rule warns arithmetic operations on optional chaining expressions, which possibly result in NaN.

How to use

To enable this rule using the config file or in the CLI, you can use:

Config (.oxlintrc.json)

{
  "rules": {
    "no-unsafe-optional-chaining": "error"
  }
}

CLI

oxlint --deny no-unsafe-optional-chaining

References

• Rule Source