exactOptionalPropertyTypes

This option makes a distinction between an optional property being not defined, and that property being explicitly set to undefined.

For example:

type SearchQuery = {
    query: string;
    filters?: Filter[];
};

it("defaults to empty filter list", () => {
    search({
        query: "asdf",
        // If exactOptionalPropertyTypes was set, this would throw in tsc
        filters: undefined,
    });
});

See a sample TS Playground for this option here

See the TSConfig reference for this option here