From aae50da0747907ac05d794b0617eadb6d1c8f8cc Mon Sep 17 00:00:00 2001
From: PouleyKetchoupp <pouleyketchoup@gmail.com>
Date: Thu, 26 Aug 2021 09:07:13 -0700
Subject: [PATCH] Fix AnimationBlendTree reset on resource loading

When reset_state was called on an existing AnimationBlendTree, the
output node would disappear, causing some errors in the editor and
preventing animations to play properly.

This change ensures the output node is always present in the node tree.
---
 scene/animation/animation_blend_tree.cpp | 7 ++++++-
 scene/animation/animation_blend_tree.h   | 2 ++
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/scene/animation/animation_blend_tree.cpp b/scene/animation/animation_blend_tree.cpp
index 049f3483ff3..d11387902a6 100644
--- a/scene/animation/animation_blend_tree.cpp
+++ b/scene/animation/animation_blend_tree.cpp
@@ -1124,6 +1124,7 @@ void AnimationNodeBlendTree::_get_property_list(List<PropertyInfo> *p_list) cons
 void AnimationNodeBlendTree::reset_state() {
 	graph_offset = Vector2();
 	nodes.clear();
+	_initialize_node_tree();
 	emit_changed();
 	emit_signal(SNAME("tree_changed"));
 }
@@ -1162,7 +1163,7 @@ void AnimationNodeBlendTree::_bind_methods() {
 	BIND_CONSTANT(CONNECTION_ERROR_CONNECTION_EXISTS);
 }
 
-AnimationNodeBlendTree::AnimationNodeBlendTree() {
+void AnimationNodeBlendTree::_initialize_node_tree() {
 	Ref<AnimationNodeOutput> output;
 	output.instantiate();
 	Node n;
@@ -1172,5 +1173,9 @@ AnimationNodeBlendTree::AnimationNodeBlendTree() {
 	nodes["output"] = n;
 }
 
+AnimationNodeBlendTree::AnimationNodeBlendTree() {
+	_initialize_node_tree();
+}
+
 AnimationNodeBlendTree::~AnimationNodeBlendTree() {
 }
diff --git a/scene/animation/animation_blend_tree.h b/scene/animation/animation_blend_tree.h
index 8508aaf71b4..258443a9991 100644
--- a/scene/animation/animation_blend_tree.h
+++ b/scene/animation/animation_blend_tree.h
@@ -345,6 +345,8 @@ class AnimationNodeBlendTree : public AnimationRootNode {
 	void _tree_changed();
 	void _node_changed(const StringName &p_node);
 
+	void _initialize_node_tree();
+
 protected:
 	static void _bind_methods();
 	bool _set(const StringName &p_name, const Variant &p_value);