I'm building a universal app using React, Redux, redux-saga, Express, Mongoose. I ran into a very strange issue: I have a simple API function that returns a Promise (the function is being used in a saga). Depending on whether it is the server or the client side it uses an axios lib to make a request or getting data from Mongoose model.

export function requestPosts() {
  if (typeof require.ensure === 'undefined') {
    const Post = require('../../../../../server/models/Post').default

        return Post.find().lean().exec()
      .then((result) => {
        const posts = normalize(result, postListSchema)
        return posts // data is correct
      })
      .catch((err) => { console.log(err) })
  } else {
    return axios.get('127.0.0.1/api/posts')
      .then((result) => {
        const posts = normalize(result.data, postListSchema)
        return posts 
      })
      .catch((err) => { throw err })
  }
}

So the thing is when it is SSR and Mongoose is used, I'm getting an error:

(node:86450) UnhandledPromiseRejectionWarning: Unhandled promise rejection (rejection id: 1): ReferenceError: e is not defined
(node:86450) DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

All goes fine if I instead of Mongoose, return a simple promise with explicit data from json file or if I use axios to make an API request to the server itself. But if only I return a promise from Mongoose or MongoDB Native Driver (which I can obtain from the Mongoose model) I'm getting the error and request is hanging.

Maybe anyone have some thoughts?