Shaders: Allow trailing commas in function calls

[akx]

This PR implements godotengine/godot-proposals#8840: allowing trailing commas in shader call function call argument lists like

vec3 fadeInTex = clamp(
  mix(-1.0, 2.0, fadeIn) + texture(fade_in_bias, UV).rgb, 
  0.0, 
  1.0,
);

• Bugsquad edit, closes: Shaders: Allow trailing commas in function calls godot-proposals#8840

[AThousandShips]

See also:

• [Shaders] Disallow trailing commas in function declarations #87075

[AThousandShips]

Haven't tested but doesn't look like this fixes:

MyStruct my_struct = MyStruct(foo, bar, );

Or

uniform float my_uniform : hint_range(0, 1, );

If we allow it explicitly in function calls these should also be allowed IMO, or it makes things more inconsistent

Further gdshaders don't allow trailing commas even in array definition, unsure if this matches glsl or not

Edit: seems glsl allows trailing comma in arrays, will look at a fix for that here as it's a parity matter

[akx]

Haven't tested but doesn't look like this fixes [struct initializers or uniform hint syntax]

No, it doesn't. Those are parsed by an entirely different part of code.

If we allow it explicitly in function calls these should also be allowed IMO, or it makes things more inconsistent

Sure, I can do that. I'm just waiting for an actual decision on godotengine/godot-proposals#8840 before doing more work that might just end up being thrown away if someone decides trailing commas should not be allowed.