GradientTexture2D causing editor to hang when quitting

[donn-xx]

Tested versions

Reproducible in commit 2124995
v4.4.dev.custom_build [2124995]

System information

Godot v4.4.dev (2124995) - Ubuntu 22.04.4 LTS 22.04 - X11 - Vulkan (Forward+) - dedicated NVIDIA GeForce RTX 2060 (nvidia; 535.183.01) - Intel(R) Core(TM) i5-9400F CPU @ 2.90GHz (6 Threads)

Issue description

Godot was hanging on Ctrl+Q and it took me some time to narrow it down to a single resource (tres) file.

If you have a GradientTexture2D resource, the editor hangs.

Steps to reproduce

Here is the tres file res://GradientTexture2D_0b38e39cdb.tres

[gd_resource type="GradientTexture2D" load_steps=2 format=3 uid="uid://dnsglu4oyarhq"]

[ext_resource type="Gradient" uid="uid://btib1unck3eqp" path="res://Gradient_70322a07ed.tres" id="1_tvpoa"]

[resource]
gradient = ExtResource("1_tvpoa")

And the Gradient res://Gradient_70322a07ed.tres

[gd_resource type="Gradient" format=3 uid="uid://btib1unck3eqp"]

[resource]

Minimal reproduction project (MRP)

All you need is those two resources in an empty project.

[KoBeWi]

Can't reproduce in 97ef3c8

[donn-xx]

Just compiled that one and tried again. Still hanging. MRP: https://gitlab.com/dbat/quit-hang-issue

[AThousandShips]

With the new MRP I can confirm on [97ef3c8], with:

ERROR: Condition "!cache.has(p_path)" is true. Returning: Dictionary()
   at: EditorResourcePreview::get_preview_metadata (godot\editor/editor_resource_preview.cpp:250)

Occurring, I suspect something preview related locks up and prevents quitting

Bisecting

[donn-xx]

How did you get to see that error? I even ran Godot with -v, but saw nothing to clue me in.

[AThousandShips]

Nothing special just my ordinary dev build

[AThousandShips]

Ouch... Wasted a bunch of time bisecting but at the same time identifying a trait of the bug:
This won't happen after the thumbnail has been generated so it will fail after it has worked once 🙃 so time to go back and redo that bisect to see where it actually works, will do that now and get back to you

[AThousandShips]

It completely locks up immediately when trying to inspect the resources in:

• ResourceLoader: Add thread-aware resource changed mechanism #96593

And doesn't lock up but does hangs on exit from:

• ResourceLoader: Fixup resource changed feature #96656

CC @RandomShaper