"[GameResource] is obsolete: declare custom resources with [AssetType]"

• A GameResource subclass compiles, but the build reports CS0618: 'GameResourceAttribute' is obsolete: 'Use AssetType instead'.
• CS0618 is a warning, so a plain dotnet build still exits green and the message is easy to miss.
• The warning only becomes a hard failure if the project treats warnings as errors, or a review gate demands zero warnings.

The old attribute used a positional constructor:

[GameResource( "Spell", "spell", "A castable spell" )]
public class SpellDefinition : GameResource { }

GameResourceAttribute is now marked obsolete in favor of AssetTypeAttribute. The compiler keeps honoring it for one more cycle, so nothing breaks yet, but the warning stands until you migrate.

Swap the attribute for [AssetType] and pass named properties instead of positional arguments:

[AssetType( Name = "Spell", Extension = "spell", Category = "My Category" )]
public class SpellDefinition : GameResource { }

The properties on Sandbox.AssetTypeAttribute (from Sandbox.Engine.xml) are Name, Extension, Category, TargetType, Flags, and IconColor.

There is no Icon property. The old [GameResource( ..., Icon = "auto_awesome" )] named argument does not carry over, so drop it during the swap. A headless dotnet build reports zero warnings and zero errors once the attribute is replaced.

Only the declaring attribute changes. The type still derives from GameResource, still produces its .ext file, and is still returned by ResourceLibrary.GetAll<T>(). [AssetType] is the current name for the same registration, so moving to it clears CS0618 without touching how the resource loads or how you query it.