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no-non-null-asserted-optional-chain

Disallows using a non-null assertion after an optional chain expression.

Rule Details​

Optional chain expressions are designed to return undefined if the optional property is nullish. Using non-null assertions after an optional chain expression is wrong, and introduces a serious type safety hole into your code.

Examples of code for this rule:

/* eslint @typescript-eslint/no-non-null-asserted-optional-chain: "error" */

foo?.bar!;
foo?.bar()!;

// Prior to TS3.9, foo?.bar!.baz meant (foo?.bar).baz - i.e. the non-null assertion is applied to the entire chain so far.
// For TS3.9 and greater, the non-null assertion is only applied to the property itself, so it's safe.
// The following is incorrect code if you're using less than TS3.9
foo?.bar!.baz;
foo?.bar!();
foo?.bar!().baz;

Options​

// .eslintrc.json
{
  "rules": {
    "@typescript-eslint/no-non-null-asserted-optional-chain": "error"
  }
}

This rule is not configurable.

When Not To Use It​

If you are not using TypeScript 3.7 (or greater), then you will not need to use this rule, as the operator is not supported.

Further Reading​

Attributes​

  • ✅ Recommended
  • 🔧 Fixable
  • 💭 Requires type information