Improve error reporting

[RenechCDDA]

Summary

Infrastructure "Improve error reporting"

Purpose of change

Our errors aren't always helpful in explaining what they mean. This confuses users (who go looking for C++ source files which they don't have) and contributors (who may troubleshoot the wrong thing until they realize what's going on).

Describe the solution

Make them more helpful.

-JSON syntax errors say they are syntax errors, to help people understand how to resolve them.

-Errors which start at the beginning of an object instead of at a member or place of error explicitly say the reported line is the beginning of the object. This has confused many, many people. Hopefully with the changes it should confuse less people.

-The line and character offset of JSON errors has been made explicit, instead of requiring you to guess what the numbers mean.

-The C++ source file names/etc were made more explicit as well, which should hopefully reduce people asking "I can't find this .cpp file on my game, where is it"

Describe alternatives you've considered

The errors which point to the start of the object could be made even better. We shouldn't even show context outside of the error object. We could also try to grab the id of the object and report that explicitly, so the contributor knows exactly what object is meant.

But that seemed like it would be a lot more difficult to implement. For example the object in question might not have an id member.

Testing

Intentionally introduce some errors, trigger the errors.

before (image from community discord):

after:

Additional context

[github-actions]

Auto-requesting reviews from non-collaborators: @andrei8l

[GuardianDll]

We apparently have an entire test suite that test errors are reported they way they are reported

[PatrikLundell]

Unfortunately, I find your last "after" image very confusion. It talks about an object beginning at a line that marks the end of an object, with the next line starting a new one.

[RenechCDDA]

We apparently have an entire test suite that test errors are reported they way they are reported

Mostly that the errors are thrown at all. But in this case since I'm updating the error messages I do need to update the messages in the tests as well. Not a big deal.

Unfortunately, I find your last "after" image very confusion. It talks about an object beginning at a line that marks the end of an object, with the next line starting a new one.

I don't really disagree, but the caret position was pre-existing. I could look into changing it.

[PatrikLundell]

Or you could change the message to match the caret position.