@storybook/api/dist/modern/lib/merge.js

Core Storybook API & Context

import mergeWith from 'lodash/mergeWith';
import isEqual from 'lodash/isEqual';
import { logger } from '@storybook/client-logger';
export default ((a, b) => mergeWith({}, a, b, (objValue, srcValue) => {
  if (Array.isArray(srcValue) && Array.isArray(objValue)) {
    srcValue.forEach(s => {
      const existing = objValue.find(o => o === s || isEqual(o, s));

      if (!existing) {
        objValue.push(s);
      }
    });
    return objValue;
  }

  if (Array.isArray(objValue)) {
    logger.log(['the types mismatch, picking', objValue]);
    return objValue;
  }

  return undefined;
}));