GDScript: Change default value for untyped exported variables

[dalexeev]

Closes #74188.

See also comments in #74231 and #75555.

Formally, this breaks compatibility, but only in a small number of cases, and we assume that users expect this behavior rather than the current one. However, it needs to be documented anyway.

[vnen]

Reviving this, do we want to move forward? I wonder what's the solution for invalid default values (e.g. when 0 is outside the range or does not belong to the define enum). AFAIK the inspector still hasn´t been fixed for those cases.

Technically, since the annotation arguments are constants we could pick a valid default, but I'm not sure if it's worth the trouble.

[dalexeev]

Reviving this, do we want to move forward? I wonder what's the solution for invalid default values (e.g. when 0 is outside the range or does not belong to the define enum). AFAIK the inspector still hasn´t been fixed for those cases.

I think this should be resolved only on the inspector's side.

• Also, I think we're a little late with this PR. I made it because you suggested this option instead of GDScript: Require type or variable initializer for export annotations #74231. But as an alternative, we could make a warning instead of an error. This would be consistent with the recently merged GDScript: Warn when enum variable has no default #90756.