tree-shaking-server-side-code-create-aot-transformers.ts

// https://github.com/angular/angular-cli/blob/bd040bd4d6d2f69b49cf7e343829027e5dbfc73d/packages/ngtools/webpack/src/ivy/transformation.ts#L14-L34
export function createAotTransformers(
  builder: ts.BuilderProgram,
  options: { emitClassMetadata?: boolean; emitNgModuleScope?: boolean },
): ts.CustomTransformers {
  const getTypeChecker = () => builder.getProgram().getTypeChecker();
  const transformers: ts.CustomTransformers = {
    before: [replaceBootstrap(getTypeChecker)],
    after: [],
  };

  const removeClassMetadata = !options.emitClassMetadata;
  const removeNgModuleScope = !options.emitNgModuleScope;
  if (removeClassMetadata || removeNgModuleScope) {
    // tslint:disable-next-line: no-non-null-assertion
    transformers.before!.push(
      removeIvyJitSupportCalls(removeClassMetadata, removeNgModuleScope, getTypeChecker),
    );
  }

  return transformers;
}