Return correct error when violating unique index

[milesrichardson]

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Environment Setup

• parse-server latest running in docker on gcloud compute server
• mongolab instance with unique constraint on column of a table

Steps to reproduce

(I've only tested this with columns of type Number, but I imagine it happens for every column type)

1. Create class SomeClass with Number column some_column
2. In Mongo, set a unique index on SomeClass.some_column
3. Save a row to SomeClass with some_column=123
4. Attempt to save another row to SomeClass with some_column=123 via the REST_API

In this case, parse-server will return the following error:

{"code":1,"message":"Internal server error."}

Whereas hosted parse will return a much more helpful error message:

{"code":137,"error":"A duplicate value for a field with unique values was provided"}

I'm calling this a "minor" issue because although the row will (correctly) fail to save, any code relying on parsing error messages (e.g. for retry logic) will break.

Interestingly, this ONLY happens when saving a SINGLE duplicate row via the REST API. When using batch operations (https://parse.com/docs/rest/guide#objects-batch-operations) to save multiple duplicate rows, or one duplicate row and one/multiple unique rows, parse-server correctly (?) returns the following message, and successfully saves the non-duplicate rows:

{"code": 11000, "error": "E11000 duplicate key error index: myapp.SomeClass.$some_column_1 dup key: { : 123 }"}

In this batch case, there is no error in the parse-server logs. However, in the saving single row case, there is an error in the parse-server logs (see below).

Logs/Trace

parse server running on http://localhost:1337/parse
Uncaught internal server error. { [MongoError: E11000 duplicate key error index: myapp.SomeClass.$some_column_1 dup key: { : 123 }]
  name: 'MongoError',
  message: 'E11000 duplicate key error index: myapp.SomeClass.$some_column_1 dup key: { : 123 }',
  driver: true,
  index: 0,
  code: 11000,
  errmsg: 'E11000 duplicate key error index: myapp.SomeClass.$some_column_1 dup key: { : 123 }' } MongoError: E11000 duplicate key error index: myapp.SomeClass.$some_column_1 dup key: { : 123 }
    at Function.MongoError.create (/parse/node_modules/mongodb-core/lib/error.js:31:11)
    at toError (/parse/node_modules/mongodb/lib/utils.js:114:22)
    at /parse/node_modules/mongodb/lib/collection.js:701:67
    at handler (/parse/node_modules/mongodb-core/lib/topologies/replset.js:400:5)
    at commandCallback (/parse/node_modules/mongodb-core/lib/topologies/server.js:1143:9)
    at Callbacks.emit (/parse/node_modules/mongodb-core/lib/topologies/server.js:116:3)
    at null.messageHandler (/parse/node_modules/mongodb-core/lib/topologies/server.js:291:23)
    at Socket.<anonymous> (/parse/node_modules/mongodb-core/lib/connection/connection.js:285:22)
    at emitOne (events.js:90:13)
    at Socket.emit (events.js:182:7)

[jcnm]

@gfosco still open as GFPR ?

[drew-gross]

Yep I'd say so.