Using relative path to cloud code file broken #1334

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• You're running the latest version of Parse Server.
• You've searched through existing issues. Chances are that your issue has been reported or resolved before.

Steps to reproduce

I've seen conflicting information regarding whether or not using a relative path to the cloud code is allowed:

var api = new ParseServer({
  cloud: './cloud/main.js',
  ...
});

The info that states it is supported:

• https://github.com/ParsePlatform/parse-server/blob/master/src/ParseServer.js#L63: // "cloud": relative location to cloud code to require
• Parse-Server-Guide wiki page: cloud: './cloud/main.js',

Places that indicate that absolute path is necessary:

• #1183: You shoud use absolute path for your cloud code.
• README.md: cloud: '/home/myApp/cloud/main.js', // Absolute path to your Cloud Code

The issue is that using ./cloud/main.js as the cloud code path actually loads [root]/node_modules/parse-server/lib/cloud/main.js, instead of the expected [root]/cloud/main.js, and it does so silently (since the require() call is successful). Once the wrong main.js file is loaded, any call to cloud code results in Error: Invalid function. (which is hard to debug).

It would be great if using ./cloud/main.js worked as expected. In my case, I'm loading my parse config from config files, so I cannot (easily) do __dirname + '/cloud/main.js'. It also seems cleaner to be able to reference the file relatively (and it makes the code that much more portable).

In some informal testing, it appears that modifying ParseServer.js to do a simple path.resolve(cloud) in the require() at line 212 allows my main.js file to be loaded correctly. I'm not familiar enough with Parse Server (or even Node.js) to suggest that as a competent solution without someone else's sanity check, but I ran the tests and they all passed (although there doesn't appear to be much testing around loading cloud code files). If someone can gut-check this solution (or propose a better one) I'd be happy to submit a PR.

If the consensus is instead that using a relative path is off the table, I can provide a PR to fix the comment, but someone else will have to fix the wiki example.