Cannot instantiate File class to read CSV file

[Blackiris]

Godot version

4.0.dev (fb821b8)

System information

Linux

Issue description

When trying to open a CSV file using this code:

extends Node

# Called when the node enters the scene tree for the first time.
func _ready():
	var file = File.new()
	file.open("res://file.csv", file.READ)

I get the following errors:

ERROR: Cannot get class 'File'.
   at: instantiate (core/object/class_db.cpp:529)
ERROR: Class type: 'File' is not instantiable.
   at: _new (modules/gdscript/gdscript.cpp:76)

The CSV file is set at Do not import.
The issue started from a commit 2 or 3 days ago, but it is hard to bisect it since many scene file formats had some changes which make them incompatible with older versions of Godot.

Steps to reproduce

Open the reproduction project and launch it

Minimal reproduction project

FileInstantiate.zip

[qarmin]

This is regression between b918c4c and fb821b8

I thinky that this commit could do this - #50511

[Blackiris]

This is regression between b918c4c and fb821b8

I thinky that this commit could do this - #50511

Hey! Nice catch! Just tried to revert this commit and it works. It is now much easier to debug. Thanks!

[akien-mga]

CC @aaronfranke

Haven't checked in depth yet but from the changes in #50511 to ClassDB, this part might have changed behavior:

I think now we're always making a copy while before we were copying only when doing a validation.
But that doesn't necessarily relate to this bug.

[akien-mga]

I think now we're always making a copy while before we were copying only when doing a validation.
But that doesn't necessarily relate to this bug.

Tested, that doesn't impact this bug indeed. I'll add a fix for this anyway in #50809.

[Blackiris]

Found it, it is here:

godot/modules/gdscript/gdscript.cpp

Lines 1647 to 1658 in 2a8a59e

	for (StringName &n : class_list) {
	String s = String(n);
	if (s.begins_with("_")) {
	n = s.substr(1, s.length());
	}
	if (globals.has(n)) {
	continue;
	}
	Ref<GDScriptNativeClass> nc = memnew(GDScriptNativeClass(n));
	_add_global(n, nc);
	}

More exactly this line:
Ref<GDScriptNativeClass> nc = memnew(GDScriptNativeClass(n));

You can see than the n value is erased here
n = s.substr(1, s.length());

Before it was,
Ref<GDScriptNativeClass> nc = memnew(GDScriptNativeClass(E->get()));
Which was the original value in the loop variable

Very small change, I will prepare a PR

[Blackiris]

Too bad, avoiding n to be erased is not enough... Got a new error

SCRIPT ERROR: Compile Error: Identifier not found: File
          at: GDScript::reload (res://new_script.gd:5)
ERROR: Method/function failed. Returning: ERR_COMPILATION_FAILED
   at: reload (modules/gdscript/gdscript.cpp:858)

Didn't try yet with PR #50809.
Don't know if @akien-mga, you could include the fix directly your PR. here is the diff:

------------------------ modules/gdscript/gdscript.cpp ------------------------
index 79cc90b92f..7015c1aa95 100644
@@ -1647,10 +1647,10 @@ void GDScriptLanguage::init() {
 	for (StringName &n : class_list) {
 		String s = String(n);
 		if (s.begins_with("_")) {
-			n = s.substr(1, s.length());
+			s = s.substr(1, s.length());
 		}
 
-		if (globals.has(n)) {
+		if (globals.has(s)) {
 			continue;
 		}
 		Ref<GDScriptNativeClass> nc = memnew(GDScriptNativeClass(n));

Worst case, I will have a look later today

[Blackiris]

Ah found it, forgot to also change line:
_add_global(n, nc);