`TypeError: type.startsWith is not a function` when starting Parse Server with custom schema data

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Issue Description

When starting Parse Server with custom schema data, the server fails to start with the error:

TypeError: type.startsWith is not a function

The error originates from MongoSchemaCollection.js, specifically in the mongoFieldToParseSchemaField function.

Steps to reproduce

1. Start Parse Server with custom MongoDB schema data(with incompatible data).
2. Server crashes during initialization with the above error.

Actual Outcome

Parse Server crashes on startup with:

TypeError: type.startsWith is not a function
at mongoFieldToParseSchemaField (C:\Users\mypre\projects\parse-server-exp\node_modules\parse-server\lib\Adapters\Storage\Mongo\MongoSchemaCollection.js:25:12)
at mongoSchemaFieldsToParseSchemaFields (C:\Users\mypre\projects\parse-server-exp\node_modules\parse-server\lib\Adapters\Storage\Mongo\MongoSchemaCollection.js:78:29)
at mongoSchemaToParseSchema (C:\Users\mypre\projects\parse-server-exp\node_modules\parse-server\lib\Adapters\Storage\Mongo\MongoSchemaCollection.js:148:13)

Expected Outcome

Parse Server should handle unexpected or malformed schema type values gracefully instead of crashing.

Root Cause

The code calls type.startsWith('relation<') without ensuring that type is a string.
If type is undefined, null, or any non-string, startsWith is not available, causing a crash.

Problematic Code

// In MongoSchemaCollection.js
if (type.startsWith('relation<')) {
  return {
    type: 'Relation',
    targetClass: type.slice('relation<'.length, type.length - 1)
  };
}

Suggested Fix

if (!type || typeof type !== 'string') {
  throw new Parse.Error(...); // Ensure type is a string before calling startsWith
}

Environment
Server

Parse Server version: 6.2.0

Operating system: Windows 11

Local or remote host: Local

Database

System: MongoDB

Database version: 7.0

Local or remote host: Local

Logs
(see error stack trace above)

Start in MongoSchemaCollection.js at mongoFieldToParseSchemaField, then trace how mongoSchemaFieldsToParseSchemaFields handles malformed custom schema data. Confirm the expected Parse Server error behavior for undefined, null, and non-string type values, and verify startup no longer exposes a raw startsWith TypeError.