Skip to main content

Disallows using a non-null assertion after an optional chain expression (no-non-null-asserted-optional-chain)

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" */


// 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

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


  • โœ… Recommended
  • ๐Ÿ”ง Fixable
  • ๐Ÿ’ญ Requires type information