Function createDeferBlockInjector

packages/core/src/defer/rendering.ts:105–148

* Creates a new injector, which contains providers collected from dependencies (NgModules) of * defer-loaded components. This function detects different types of parent injectors and creates * a new injector based on that.

(
  parentInjector: Injector,
  tDetails: TDeferBlockDetails,
  providers: Provider[],
)

 * a new injector based on that.
 */
function createDeferBlockInjector(
  parentInjector: Injector,
  tDetails: TDeferBlockDetails,
  providers: Provider[],
) {
  // Check if the parent injector is an instance of a `ChainedInjector`.
  //
  // In this case, we retain the shape of the injector and use a newly created
  // `EnvironmentInjector` as a parent in the `ChainedInjector`. That is needed to
  // make sure that the primary injector gets consulted first (since it's typically
  // a NodeInjector) and `EnvironmentInjector` tree is consulted after that.
  if (parentInjector instanceof ChainedInjector) {
    const origInjector = parentInjector.injector;
    // Guaranteed to be an environment injector
    const parentEnvInjector = parentInjector.parentInjector;

    const envInjector = getOrCreateEnvironmentInjector(parentEnvInjector, tDetails, providers);
    return new ChainedInjector(origInjector, envInjector);
  }

  const parentEnvInjector = parentInjector.get(EnvironmentInjector);

  // If the `parentInjector` is *not* an `EnvironmentInjector` - we need to create
  // a new `ChainedInjector` with the following setup:
  //
  //  - the provided `parentInjector` becomes a primary injector
  //  - an existing (real) `EnvironmentInjector` becomes a parent injector for
  //    a newly-created one, which contains extra providers
  //
  // So the final order in which injectors would be consulted in this case would look like this:
  //
  //  1. Provided `parentInjector`
  //  2. Newly-created `EnvironmentInjector` with extra providers
  //  3. `EnvironmentInjector` from the `parentInjector`
  if (parentEnvInjector !== parentInjector) {
    const envInjector = getOrCreateEnvironmentInjector(parentEnvInjector, tDetails, providers);
    return new ChainedInjector(parentInjector, envInjector);
  }

  // The `parentInjector` is an instance of an `EnvironmentInjector`.
  // No need for special handling, we can use `parentInjector` as a
  // parent injector directly.
  return getOrCreateEnvironmentInjector(parentInjector, tDetails, providers);
}

/** Rendering Helpers */