Support Core logging

[thekevinbrown]

Goals

Things don't always go as expected. Developers should have a way to enable a sort of trace logging with Realm so they can see what it's doing in a production application. Without logging we have to go through a lot of extra work to narrow down performance issues.

Expected Results

There should be a way to enable logging, either by configuring Realm, or for performance reasons packaging up the logging version as a different NPM dependency.

Actual Results

The only way to debug what Realm is doing is to guess at what might be causing a problem and remove it.

Steps to Reproduce

Have someone that is not familiar with Realm trying to make a repro to demo a bug. It takes a lot longer than it should.

Code Sample

Not relevant

Version of Realm and Tooling

• Realm JS SDK Version: Any
• Node or React Native: Any
• Client OS & Version: Any
• Which debugger for React Native: None

Note

This issue was originally raised as #2499, I'm splitting it out because multiple separate and unconnected issues were discovered in exploring there.

[sync-by-unito]

➤ papafe commented:

Started working on this, agreed with the team to

• add setLogger and setLogLevel as static methods on Realm
• deprecate the previous API (logger set only on the sync manager)
• logLevel to be a union type of string, and use it for both the logger callback and the setting the log level
• add a new method to the helper to create a logger, and make the previous logger factory creation to use this new method

Planning to finish this at most by the end of next week.