Writing and interpreting GDScript in real time?

[smorty]

Godot Version

4.4 RC 1

Question

I want to have the ability to convert a string with GDScript code in it and convert it to a GDScript resource (which extends Script, which extends Resource).

The .new() constructor however instantiates the script to the object it should contain, and doesn’t actually create a new instance of GDScript.

Is there some way i can kinda do this:

extends Node

var my_script := """extends Node

func get_some_data() -> String:
    return "Hello World!"
"""

func _ready():
    # Create new GDScript with the my_script code
    var gdscript:GDScript = GDScript.new()
    var gdscript.source_code = my_script

    # creates a new node of that type and adds it to the tree
    var script_instance:Node = gdscript.instantiate()
    add_child(script_instance)

    # Print the results of the script, Should be "Hello World"
    var script_output:String = script_instance.get_some_data()
    print("Script output: ", script_output)

This would be like - SUPER helpful for designing ingame tools and stuff.

EDIT: I am aware that I could store the GDScript as some my_script.gd file, then load() it and then instantiate it… but that feels like a hacky solution which might override some other files which are already present.

[herrspaten]

Maybe Expressions is what you are looking for. Note that this has obvious security risks

[burning-banana]

If you just need to overwrite functionality based on a resource, you can change the attached script of a resource in the editor.

[ratrogue]

Expressions are very limited, they don’t even allow creating new variables.

[gertkeno]

You must reload the script after editing it’s source.

var gdscript:GDScript = GDScript.new()
gdscript.source_code = my_script

var err := gdscript.reload()
assert(err == OK, "Couldn't compile script")

var script_instance = gdscript.new()

This isn’t sandboxed so the script has full access to your game’s internals and the operator’s computer. You may want to look into Lua plugins instead.

[smorty]

Thank you, that seemed to have worked!

I have to ask something again though, something I asked some months ago but didn’t get an answer to:

Is it then possible to retrieve the errors from a script, or is that only possible within C?

[gertkeno]

The specific line number/parser errors will be pushed to the output or stack trace, Godot does not have a way to catch those errors, they only return var err in my example which can assess failure.