Global shader sampler2d uniforms are blank

[A-Hugh-Mann]

Tested versions

Reproducible in 4.5.dev.03bd8ba9c

System information

Arch Linux Vulkan (Forward+) - Dedicated AMD Radeon RX 6600 (RADV NAVI23)

Issue description

When attempting to read a sampler2D within a shader that is a global uniform from the project settings, the image will be all white instead of what is intended or set.

Steps to reproduce

Create a new project

go into project settings and add go to shader globals, then add a new one named "test", as a sampler2D type.
set that test to any image you want, or even a NoiseTexture with the apropriate noise generator and such, to make a texture that can be seen.

create a sprite2d, or anything visible, it doesnt matter what

set a ShaderMaterial for its material

give it one of these shaders
for 2d:

shader_type canvas_item;
global uniform sampler2D test : source_color;
void fragment() {
	COLOR = texture(test, UV);
}

for 3d:

shader_type spatial;
global uniform sampler2D test : source_color;
void fragment() {
	ALBEDO = texture(test, UV).rgb;
}

Minimal reproduction project (MRP)

N/A

[beicause]

I can confirm it in master but it doesn't appear in 4.5.dev5.

Also when I save global uniform texture and reload the project, the texture isn't saved and becomes empty.

[akien-mga]

It would be very useful to bisect if you can.

[beicause]

It would be very useful to bisect if you can.

This is a regression from #101941.

Also when I save global uniform texture and reload the project, the texture isn't saved and becomes empty.

It's a separate issue. Actually, project.godot never saves embedded resources, it only stores resource paths:

[shader_globals]

tex_arr={
"type": "sampler2DArray",
"value": ""
}
tex={
"type": "sampler2D",
"value": "res://new_gradient_texture_2d.tres"
}

So embedded resources will be quietly lost after reloading, unless they are saved to paths. it can also be reproduced in 4.4. A possible solution is displaying a warning when there are unsaved resources in global shader uniform.