[WIP] Add logging support

[mitchcurtis]

This patch adds a debug_log() function (log() was taken; the name is up for discussion) to GDScript. The goals are to:

• Allow logging that is only executed in debug builds.
• Allow logging to different categories, which can be enabled/disabled in e.g. project settings.
• Allow specifying a message pattern (e.g. in project settings) to enable things like timestamps to be included in the logged messages (see e.g. https://doc.qt.io/qt-5/qtglobal.html#qSetMessagePattern).
• Allow logging to either the console or a file.

Closes #27958.

[mitchcurtis]

Opening this early so I can get early feedback.

What do you think about the goals of this patch?

I'm also curious to what extent (if any) this should use the existing Logger API internally.

[fire]

You may be able to use and improve on this function for timestamps. get_iso_date_time

[Calinou]

As a stretch goal, maybe we could have a setting to output all logging messages as JSON. This would be useful to feed a dedicated server's console output to a log aggregation tool such as Loki.

[mitchcurtis]

As a stretch goal, maybe we could have a setting to output all logging messages as JSON. This would be useful to feed a dedicated server's console output to a log aggregation tool such as Loki.

Sounds fairly straightforward, assuming there's already a way to write JSON to a text file?

[Calinou]

@mitchcurtis You would just need to print the JSON to standard output (one JSON object per line, that is). Writing to a file should be handled by writing that standard output to a file, as is already done by the Logging > File Logging > Enable File Logging project setting.

[mitchcurtis]

Is there a way I can suppress the notifications for reviewers until I'm ready? I still have a lot of work to do... perhaps I should have just kept this as a branch on my fork. :x

Edit: there are drafts, but you can't convert a regular pull request to a draft, only the other way around: https://github.saobby.my.eu.orgmunity/t5/How-to-use-Git-and-GitHub/Feature-Request-Switch-from-ready-to-draft-in-pull-requests/td-p/19107/page/2

[mitchcurtis]

@bojidar-bg do you know why I'd be getting this warning:

W 0:00:00:0447 Standalone expression (the line has no effect).

Scene.gd:5

for this:

extends Node2D

func _init():
    log_debug("MyCategory", "doing some stuff involving MyCategory")

I can see logging output in Creator's output panel, but not in Godot's.

[Calinou]

Remember to update the messages to remove references to debug_log and instead refer to the correct logging function 🙂

[aaronfranke]

@mitchcurtis Is this still desired? If so, it needs to be rebased on the latest master branch. Also, the above feedback should be addressed. Also, since this PR is a feature proposal, you should consider opening a proposal which explains example use cases and how this approach will solve the problem.

Otherwise, abandoned pull requests will be closed in the future as announced here.