return (tree: Tree, context: SchematicContext) => {
    if (!options.name) {
      throw new SchematicsException('name option is required.');
    }

    let collectionPath: Path | undefined;
    try {
      const packageJsonContent = tree.read('/package.json');
      if (packageJsonContent) {
        const packageJson = JSON.parse(packageJsonContent.toString('utf-8'));
        if ('schematics' in packageJson) {
          const p = normalize(packageJson['schematics']);
          if (tree.exists(p)) {
            collectionPath = p;
          }
        }
      }
    } catch (_) {
    }

    let source = apply(url('./schematic-files'), [
        applyTemplates({
          ...options as object,
          coreVersion,
          schematicsVersion,
          dot: '.',
          camelize: strings.camelize,
          dasherize: strings.dasherize,
        }),
      ]);

    // Simply create a new schematic project.
    if (!collectionPath) {
      collectionPath = normalize('/' + options.name + '/src/collection.json');
      source = apply(url('./project-files'), [
        applyTemplates({
          ...options as object,
          coreVersion,
          schematicsVersion,
          dot: '.',
          camelize: strings.camelize,
          dasherize: strings.dasherize,
        }),
        mergeWith(source),
        move(options.name),
      ]);

      context.addTask(new NodePackageInstallTask(options.name));
    }

    return chain([
      mergeWith(source),
      addSchematicToCollectionJson(collectionPath, strings.dasherize(options.name), {
        description: 'A blank schematic.',
        factory: './' + strings.dasherize(options.name) + '/index#' +
          strings.camelize(options.name),
      }),
    ]);
  };

  return async (host: Tree, context: SchematicContext) => {
    const workspace = await getWorkspace(host);

    const clientProject = workspace.projects.get(options.clientProject);
    if (!clientProject || clientProject.extensions.projectType !== 'application') {
      throw new SchematicsException(`Universal requires a project type of "application".`);
    }

    const clientBuildTarget = clientProject.targets.get('build');
    if (!clientBuildTarget) {
      throw targetBuildNotFoundError();
    }
    const clientBuildOptions =
      (clientBuildTarget.options || {}) as unknown as BrowserBuilderOptions;

    const outDir = getTsConfigOutDir(host, clientBuildOptions.tsConfig);

    const clientTsConfig = normalize(clientBuildOptions.tsConfig);
    const tsConfigExtends = basename(clientTsConfig);
    // this is needed because prior to version 8, tsconfig might have been in 'src'
    // and we don't want to break the 'ng add @nguniversal/express-engine schematics'
    const rootInSrc = clientProject.root === '' && clientTsConfig.includes('src/');
    const tsConfigDirectory = join(normalize(clientProject.root), rootInSrc ? 'src' : '');

    if (!options.skipInstall) {
      context.addTask(new NodePackageInstallTask());
    }

    const templateSource = apply(url('./files/src'), [
      applyTemplates({
        ...strings,
        ...options as object,
        stripTsExtension: (s: string) => s.replace(/\.ts$/, ''),
      }),
      move(join(normalize(clientProject.root), 'src')),
    ]);

    const rootSource = apply(url('./files/root'), [
      applyTemplates({
        ...strings,
        ...options as object,
        stripTsExtension: (s: string) => s.replace(/\.ts$/, ''),
        outDir,
        tsConfigExtends,
        rootInSrc,
      }),
      move(tsConfigDirectory),
    ]);

    return chain([
      mergeWith(templateSource),
      mergeWith(rootSource),
      addDependencies(),
      updateConfigFile(options, tsConfigDirectory),
      wrapBootstrapCall(clientBuildOptions.main),
      addServerTransition(options, clientBuildOptions.main, clientProject.root),
    ]);
  };

  return (host: Tree, context: SchematicContext) => {
    if (!options.name) {
      throw new SchematicsException(`Invalid options, "name" is required.`);
    }
    validateProjectName(options.name);
    let newProjectRoot = '';
    try {
      const workspace = getWorkspace(host);
      newProjectRoot = workspace.newProjectRoot || '';
    } catch {
    }
    const appDir = `${newProjectRoot}/${options.name}`;

    // If user already has angular installed, Bazel should use that version
    const existingAngularVersion = findAngularVersion(options, host);

    const workspaceVersions = {
      'ANGULAR_VERSION': existingAngularVersion || '7.1.1',
      'RULES_SASS_VERSION': '1.14.1',
      'RXJS_VERSION': '6.3.3',
    };

    return mergeWith(apply(url('./files'), [
      applyTemplates({
        utils: strings,
        ...options,
        'dot': '.', ...workspaceVersions,
      }),
      move(appDir),
    ]));
  };

  return (host: Tree, context: SchematicContext) => {
    context.logger.debug('updating project configuration.');

    // Add worker glob exclusion to tsconfig.app.json.
    const workerGlob = 'src/**/*.worker.ts';
    const buffer = host.read(tsConfigPath);
    if (buffer) {
      const tsCfgAst = parseJsonAst(buffer.toString(), JsonParseMode.Loose);
      if (tsCfgAst.kind != 'object') {
        throw new SchematicsException('Invalid tsconfig. Was expecting an object');
      }
      const filesAstNode = findPropertyInAstObject(tsCfgAst, 'exclude');
      if (filesAstNode && filesAstNode.kind != 'array') {
        throw new SchematicsException('Invalid tsconfig "exclude" property; expected an array.');
      }

      if (filesAstNode && !filesAstNode.value.includes(workerGlob)) {
        const recorder = host.beginUpdate(tsConfigPath);
        appendValueInAstArray(recorder, filesAstNode, workerGlob);
        host.commitUpdate(recorder);
      }
    }

    return mergeWith(
      apply(url('./files/worker-tsconfig'), [
        applyTemplates({
          ...options,
          relativePathToWorkspaceRoot: relativePathToWorkspaceRoot(root),
        }),
        move(root),
      ]),
    );
  };

  return (host: Tree, context: SchematicContext) => {
    const name = options.name || getWorkspace(host).defaultProject;
    if (!name) {
      throw new Error('Please provide a name for Bazel workspace');
    }
    validateProjectName(name);

    if (!host.exists('yarn.lock')) {
      host.create('yarn.lock', '');
    }

    const workspaceVersions = {
      'RULES_NODEJS_VERSION': '0.18.6',
      'RULES_NODEJS_SHA256': '1416d03823fed624b49a0abbd9979f7c63bbedfd37890ddecedd2fe25cccebc6',
      'RULES_SASS_VERSION': '1.17.0',
    };

    return mergeWith(apply(url('./files'), [
      applyTemplates({
        utils: strings,
        name,
        'dot': '.', ...workspaceVersions,
        routing: hasRoutingModule(host),
        sass: hasSassStylesheet(host),
      }),
    ]));
  };