Fix VariantResource converting from null

core/types/variant_resource.cpp

@@ -1,15 +1,23 @@
 #include "variant_resource.h"
 
 void VariantResource::set_type(Variant::Type p_type) {
+	const Variant::Type prev_type = type;
 	type = p_type;
 	// Convert previous value to a new type, if possible.
-	if (value.get_type() != Variant::NIL) {
+	if (prev_type != Variant::NIL) {
 		value = convert(value, type);
+	} else {
+		value = create(type);
 	}
 	emit_changed();
 	_change_notify();
 }
 
+Variant VariantResource::create(const Variant::Type &p_type) {
+	Variant::CallError error;
+	return Variant::construct(p_type, nullptr, 0, error);
+}
+
 Variant VariantResource::convert(const Variant &p_value, const Variant::Type &p_to_type) {
 	Variant::CallError error;
 	const Variant *args[1];

core/types/variant_resource.h

@@ -4,8 +4,6 @@
 #include "core/resource.h"
 #include "core/variant.h"
 
-class VariantResource;
-
 class VariantResource : public Resource {
 	GDCLASS(VariantResource, Resource);
 
@@ -23,11 +21,10 @@ class VariantResource : public Resource {
 	void set_type(Variant::Type p_type);
 	int get_type() const { return type; }
 
+	static Variant create(const Variant::Type &p_type);
 	static Variant convert(const Variant &p_value, const Variant::Type &p_to_type);
 
 	virtual String to_string() { return String(value); }
-
-	VariantResource() {}
 };
 
 #endif // GOOST_VARIANT_RESOURCE_H

doc/VariantResource.xml

@@ -4,7 +4,7 @@
 		A [Resource] which holds any [Variant] compatible type.
 	</brief_description>
 	<description>
-		This class allows to store any [Variant] compatible built-in types as a [Resource], such as [Vector2], [Dictionary], [Array], and even [VariantResource] itself. These can be edited in the inspector and saved to disk to be reused throughout the project, as resources are shared between instances by default.
+		This class allows to store any [Variant] compatible built-in types as a [Resource], such as [Vector2], [Dictionary], [Array], and even nested[VariantResource]s themselves. These can be edited in the inspector and saved to disk to be reused throughout the project, as resources are shared between instances by default.
 		[VariantResource] is normally edited via the editor inspector, but the [member type] and [code]value[/code] can be changed via code as well:
 		[codeblock]
 		var res = VariantResource.new()
@@ -13,7 +13,7 @@
 		res.type = TYPE_VECTOR2 # The previous value is converted to a new type.
 		print(res.value)  # prints (1, 2)
 		[/codeblock]
-		The conversion logic is mostly equivalent to [method @GDScript.convert], except that the [constant @GlobalScope.TYPE_NIL] is never automatically converted to other types.
+		The conversion logic is mostly equivalent to [method @GDScript.convert], except that the [constant @GlobalScope.TYPE_NIL] is never automatically converted to other types, and a new empty [Variant] is constructed instead.
 	</description>
 	<tutorials>
 	</tutorials>
@@ -26,7 +26,7 @@
 			[codeblock]
 			extends Node2D
 
-			export(VariantResource) res = VariantResource.new()
+			export(VariantResource) var res = VariantResource.new()
 
 			func _ready():
 			    # Whenever the color is changed, redraw the canvas.

tests/project/goost/core/types/test_variant_resource.gd

@@ -36,11 +36,23 @@ func test_set_value_convert_type():
 func test_changed_signal():
 	watch_signals(res)
 	res.value = "Godot"
-	var err = res.connect("changed", self, "_on_changed", [res])
+	var err = res.connect("changed", self, "_on_changed", [res], CONNECT_ONESHOT)
 	assert_eq(err, OK)
 	res.value = "Goost"
 	assert_signal_emitted(res, "changed")
 
 
 func _on_changed(p_res):
 	assert_eq(p_res.value, "Goost")
+
+
+func test_convert_from_null_to_string():
+	res.value = null
+	assert_eq(res.type, TYPE_NIL)
+
+	res.type = TYPE_STRING
+	assert_ne(res.value, "Null")
+	assert_ne(res.value, "Nil")
+	assert_ne(res.value, "null")
+	assert_ne(res.value, "nil")
+	assert_eq(res.value, "")