@typescript-eslint/no-extra-non-null-assertion

! after an expression tells TypeScript that the value isn't null or undefined. Writing it twice, as in user!!, doesn't add anything. Writing it right before ?. contradicts itself, because user!?.name first claims that user is there and then checks whether it is.

--fix removes the extra !.

This rule is on by default in TypeScript files.

Configure

On by default as a warning. To turn it off:

[lint.rules]
"@typescript-eslint/no-extra-non-null-assertion" = "off" # or "error"

Examples

Reported:

function nameOf(user?: { name: string }) {
  return user!!.name;
}

function lengthOf(items?: string[]) {
  return items!?.length;
}

Not reported:

function nameOf(user?: { name: string }) {
  return user!.name;
}

function lengthOf(items?: string[]) {
  return items?.length;
}