getStorybookMain.ts

import { join, resolve } from 'path';
import { serverRequire } from '@storybook/core-common';
import type { StorybookConfig } from '@storybook/types';
import dedent from 'ts-dedent';

let storybookMainConfig: StorybookConfig;

export const getStorybookMain = (configDir: string) => {
  if (storybookMainConfig) {
    return storybookMainConfig;
  }

  storybookMainConfig = serverRequire(join(resolve(configDir), 'main'));

  if (!storybookMainConfig) {
    throw new Error(
      `Could not load main.js in ${configDir}. Is the config directory correct? You can change it by using --config-dir <path-to-dir>`
    );
  }

  if (!storybookMainConfig.stories || storybookMainConfig.stories.length === 0) {
    throw new Error(
      dedent`
        Could not find stories in main.js in ${configDir}. 
        If you are using a mono-repository, please run the test-runner only against your sub-package, which contains a .storybook folder with "stories" defined in main.js.
        You can change the config directory by using --config-dir <path-to-dir>
        `
    );
  }

  return storybookMainConfig;
};