Returning undefined in cloud code throws error

[dplewis]

Issue Description

Similar to parse-community/Parse-SDK-JS#417

Steps to reproduce

Parse.Cloud.define('returnUndefined', () => {
  return undefined;
});

Expected Results

return undefined / null
not throw error

Actual Outcome

Unhandled Promise Rejection: Error: The server returned an invalid response.

Environment Setup

• Server

  • parse-server version (Be specific! Don't say 'latest'.) : 3.0.0
  • Operating System: Mac OSX
  • Localhost or remote server? (AWS, Heroku, Azure, Digital Ocean, etc): localhost

• Database

  • MongoDB version: Mongo
  • Localhost or remote server? (AWS, mLab, ObjectRocket, Digital Ocean, etc): localhost

Logs/Trace

info: Ran cloud function returnUndefined for user undefined with:
  Input: {}
  Result: undefined functionName= returnUndefined, , user=undefined
verbose: RESPONSE from [POST] /parse/functions/returnVoid: {
  "response": {}
} result=undefined

[SebC99]

We've discussed this here:
#4818

[dplewis]

@SebC99 PR? @flovilmart is forcing return null ok?

[SebC99]

@dplewis there was no real consensus on the solution and on the impact on SDKs:

• solution 1: return null instead of undefined before stringifying the json. Should have no impact on SDK as null would be understand well in JS and iOS (I don't know for Android)
• solution 2: just display a warning on server side to avoid undefined results, but we will still have the issue
• solution 3: add a status field next to the result field in the json to avoid empty json, which could be ignore by SDKs at first to have no impact.

[flovilmart]

Do we need to address that? Or we’re bikeshedding for nothin? I have no trouble considering undefined as an invalid response :)

[dplewis]

The rest api returns {}, iOS returns null, JS returns unhandled promise rejection.

We can at least get rid of the unhandled rejection with a catch

https://github.com/parse-community/Parse-SDK-JS/blob/master/src/Cloud.js#L129

[flovilmart]

Uhm ok. On iOS can you show me the equivalent code?

[dplewis]

https://github.com/parse-community/Parse-SDK-iOS-OSX/blob/master/Parse/Parse/Internal/CloudCode/PFCloudCodeController.m#L62

[flovilmart]

alright, that kinda sucks, as in iOS it ends up being decode:nil.

let's support it on the JS SDK.

[dplewis]

Closed via parse-community/Parse-SDK-JS#682