# @typescript-eslint/no-non-null-asserted-optional-chain

> Disallow `!` after an optional chain

`user?.name` is `undefined` when `user` is missing. That's what `?.` is for. A `!` after it tells TypeScript the result is never `undefined`, so the type no longer matches what happens at runtime, and the next line that uses the value can throw.

If `user` is always there, you don't need `?.`. If it isn't, handle the `undefined`.

This rule is on by default in TypeScript files.

{/* Generated by src/codegen/lint-rule-docs.ts. Do not edit this section. */}

## Configure

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

```toml bunfig.toml
[lint.rules]
"@typescript-eslint/no-non-null-asserted-optional-chain" = "off" # or "error"
```

{/* End of the generated section. */}

## Examples

Reported:

{/* bad {"count": 2} */}
```ts
declare const user: { name: string; address?: { city: string } } | undefined;

const name: string = user?.name!;
const city: string = (user?.address?.city)!;
```

Not reported:

{/* good */}
```ts
declare const user: { name: string; address?: { city: string } } | undefined;

const name: string = user?.name ?? "guest";
const city: string | undefined = user?.address?.city;
```

A `!` in the middle of the chain is allowed. Here it only applies to `address`, and only when there's a `user`:

{/* good */}
```ts
declare const user: { name: string; address?: { city: string } } | undefined;

const city: string | undefined = user?.address!.city;
```