no-non-null-asserted-optional-chain
)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 incorrect 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;
Examples of correct code for this rule:
/* eslint @typescript-eslint/no-non-null-asserted-optional-chain: "error" */ foo?.bar; (foo?.bar).baz; foo?.bar(); foo?.bar(); foo?.bar().baz; // The following is correct code if you're using TS3.9 or greater foo?.bar!.baz; foo?.bar!(); foo?.bar!().baz;
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.