New hook to allow Trapdoors be climbable for custom ladders (#7816)

src/main/java/net/minecraftforge/common/extensions/IForgeBlock.java

@@ -116,6 +116,20 @@ public interface IForgeBlock
         return state.getBlock().is(BlockTags.CLIMBABLE);
     }
 
+    /**
+     * Checks if this block makes an open trapdoor above it climbable.
+     *
+     * @param state The current state
+     * @param world The current world
+     * @param pos Block position in world
+     * @param trapdoorState The current state of the open trapdoor above
+     * @return True if the block should act like a ladder
+     */
+    default boolean makesOpenTrapdoorAboveClimbable(BlockState state, IWorldReader world, BlockPos pos, BlockState trapdoorState)
+    {
+        return state.getBlock() instanceof LadderBlock && state.getValue(LadderBlock.FACING) == trapdoorState.getValue(TrapDoorBlock.FACING);
+    }
+
     /**
      * Determines if this block should set fire and deal fire damage
      * to entities coming into contact with it.