Add getDataOrDefault method to FabricRenderState (#4917)

Author: 8s2

fabric-rendering-v1/src/client/java/net/fabricmc/fabric/api/client/rendering/v1/FabricRenderState.java

@@ -46,6 +46,17 @@ default <T> T getData(RenderStateDataKey<T> key) {
 		throw new UnsupportedOperationException("Implemented via mixin");
 	}
 
+	/**
+	 * Get extra render data from the render state, or a default value if it cannot be found.
+	 * @param key the key of the data
+	 * @param defaultValue the default value
+	 * @param <T> the type of the data
+	 * @return the data, or the default value if it cannot be found.
+	 */
+	default <T> T getDataOrDefault(RenderStateDataKey<T> key, T defaultValue) {
+		throw new UnsupportedOperationException("Implemented via mixin");
+	}
+
 	/**
 	 * Set extra render data to the render state.
 	 * @param key the key of the data

fabric-rendering-v1/src/client/java/net/fabricmc/fabric/mixin/client/rendering/RenderStateMixin.java

@@ -48,6 +48,12 @@ public abstract class RenderStateMixin implements FabricRenderState {
 		return renderStateData == null ? null : (T) renderStateData.get(key);
 	}
 
+	@Override
+	@SuppressWarnings("unchecked")
+	public <T> T getDataOrDefault(RenderStateDataKey<T> key, T defaultValue) {
+		return renderStateData == null ? defaultValue : (T) renderStateData.getOrDefault(key, defaultValue);
+	}
+
 	@Override
 	public <T> void setData(RenderStateDataKey<T> key, T value) {
 		if (renderStateData == null) {

fabric-rendering-v1/src/test/java/net/fabricmc/fabric/impl/client/rendering/state/RenderStateDataTest.java

@@ -65,10 +65,13 @@ itemRenderState.new LayerRenderState(),
 
 		for (FabricRenderState state : states) {
 			Assertions.assertNull(state.getData(DEBUG));
+			Assertions.assertEquals("pass", state.getDataOrDefault(DEBUG, "pass"));
 			state.setData(DEBUG, "test");
 			Assertions.assertEquals("test", state.getData(DEBUG));
+			Assertions.assertEquals("test", state.getDataOrDefault(DEBUG, "fail"));
 			state.clearExtraData();
 			Assertions.assertNull(state.getData(DEBUG));
+			Assertions.assertEquals("pass", state.getDataOrDefault(DEBUG, "pass"));
 		}
 	}
 }