LocatorFnResult - Angular

The result type obtained when searching using a particular list of queries. This type depends on the particular items being queried.

If one of the queries is for a ComponentHarnessConstructor<C1>, it means that the result might be a harness of type C1
If one of the queries is for a HarnessPredicate<C2>, it means that the result might be a harness of type C2
If one of the queries is for a string, it means that the result might be a TestElement.

API

type LocatorFnResult<T extends (HarnessQuery<any> | string)[]> = {
  [I in keyof T]: T[I] extends new (...args: any[]) => infer C // Map `ComponentHarnessConstructor<C>` to `C`.
    ? C
    : // Map `HarnessPredicate<C>` to `C`.
      T[I] extends {harnessType: new (...args: any[]) => infer C}
      ? C
      : // Map `string` to `TestElement`.
        T[I] extends string
        ? TestElement
        : // Map everything else to `never` (should not happen due to the type constraint on `T`).
          never;
}[number]

Description

The result type obtained when searching using a particular list of queries. This type depends on the particular items being queried.

If one of the queries is for a ComponentHarnessConstructor<C1>, it means that the result might be a harness of type C1
If one of the queries is for a HarnessPredicate<C2>, it means that the result might be a harness of type C2
If one of the queries is for a string, it means that the result might be a TestElement.

Since we don't know for sure which query will match, the result type if the union of the types for all possible results.

Usage Notes

Example

The type:

LocatorFnResult<[
  ComponentHarnessConstructor<MyHarness>,
  HarnessPredicate<MyOtherHarness>,
  string
]>

is equivalent to:

MyHarness | MyOtherHarness | TestElement