Internal server error on set followed by unset

[mstniy]

New Issue Checklist

• [x] I am not disclosing a vulnerability.
• [x] I am not just asking a question.
• [x] I have searched through existing issues.
• [x] I can reproduce the issue with the latest version of Parse Server.

Issue Description

Setting a subdocument entirely, followed by an unset of a nested field causes an internal server error while the object is being saved, if the object existed beforehand.

Steps to reproduce

const myObj = new Parse.Object('MyClass');
await myObj.save(null, {useMasterKey: true});
myObj.set('data', {a: 5});
myObj.unset('data.a');
await myObj.save(null, {useMasterKey: true});
console.log('a');

Actual Outcome

error: Uncaught internal server error. Updating the path 'data.a' would create a conflict at 'data' {"code":40,"codeName":"ConflictingUpdateOperators","ok":0,"stack":"MongoServerError: Updating the path 'data.a' would create a conflict at 'data'\n    at Connection.onMessage (/home/kartal/Desktop/ocell/parse-server-example/node_modules/parse-server/node_modules/mongodb/lib/cmap/connection.js:202:30)\n    at MessageStream.<anonymous> (/home/kartal/Desktop/ocell/parse-server-example/node_modules/parse-server/node_modules/mongodb/lib/cmap/connection.js:62:60)\n    at MessageStream.emit (events.js:400:28)\n    at processIncomingData (/home/kartal/Desktop/ocell/parse-server-example/node_modules/parse-server/node_modules/mongodb/lib/cmap/message_stream.js:108:16)\n    at MessageStream._write (/home/kartal/Desktop/ocell/parse-server-example/node_modules/parse-server/node_modules/mongodb/lib/cmap/message_stream.js:28:9)\n    at writeOrBuffer (internal/streams/writable.js:358:12)\n    at MessageStream.Writable.write (internal/streams/writable.js:303:10)\n    at Socket.ondata (internal/streams/readable.js:731:22)\n    at Socket.emit (events.js:400:28)\n    at addChunk (internal/streams/readable.js:293:12)"}
MongoServerError: Updating the path 'data.a' would create a conflict at 'data'
    at Connection.onMessage (/home/kartal/Desktop/ocell/parse-server-example/node_modules/parse-server/node_modules/mongodb/lib/cmap/connection.js:202:30)
    at MessageStream.<anonymous> (/home/kartal/Desktop/ocell/parse-server-example/node_modules/parse-server/node_modules/mongodb/lib/cmap/connection.js:62:60)
    at MessageStream.emit (events.js:400:28)
    at processIncomingData (/home/kartal/Desktop/ocell/parse-server-example/node_modules/parse-server/node_modules/mongodb/lib/cmap/message_stream.js:108:16)
    at MessageStream._write (/home/kartal/Desktop/ocell/parse-server-example/node_modules/parse-server/node_modules/mongodb/lib/cmap/message_stream.js:28:9)
    at writeOrBuffer (internal/streams/writable.js:358:12)
    at MessageStream.Writable.write (internal/streams/writable.js:303:10)
    at Socket.ondata (internal/streams/readable.js:731:22)
    at Socket.emit (events.js:400:28)
    at addChunk (internal/streams/readable.js:293:12)

Expected Outcome

The object should be saved to the database with data = {}

Environment

Server

• Parse Server version: 5.3.0
• Operating system: ubuntu 20.04
• Local or remote host (AWS, Azure, Google Cloud, Heroku, Digital Ocean, etc): local

Database

• System (MongoDB or Postgres): MongoDB
• Database version: 5.0.13
• Local or remote host (MongoDB Atlas, mLab, AWS, Azure, Google Cloud, etc): local

Client

• SDK (iOS, Android, JavaScript, PHP, Unity, etc): parse dashboard
• SDK version: 4.1.4

Logs

[parse-github-assistant[bot]]

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[mtrezza]

Nice find! Do you want to open a PR? This may well be a Parse JS SDK issue rather than a Parse Server issue, if the SDK doesn't handle this set / unset properly. Did you look at what the SDK sends to the server?

[mstniy]

I have verified that the SDK sends a malformed request to the server, so this is an SDK issue.

[mtrezza]

Great, would you want to open a PR with a failing test?

[mtrezza]

@mstniy Do you have any more infos on this issue? Otherwise I'll transfer it to the Parse JS SDK.

[mstniy]

I am afraid not, @mtrezza . Feel free to transfer the issue. We ended up working around it.

[mortenmo]

Looking at this for a moment, not sure there isn't more related issues.

Trying to just add data.b (not unsetting) and trying to get it after removes locally the previous value. It doesn't merge the ops locally.

I didn't realize dot notation was even supported on set/get, but there seem to be a lot of issues with it.