[1.17.x] implements canConnectRedstone(), Redstone dust now defers to the blockstate for determining connectivity (#8014)

patches/minecraft/net/minecraft/world/level/block/RedStoneWireBlock.java.patch

@@ -0,0 +1,27 @@
+--- a/net/minecraft/world/level/block/RedStoneWireBlock.java
++++ b/net/minecraft/world/level/block/RedStoneWireBlock.java
+@@ -199,7 +_,7 @@
+       BlockState blockstate = p_55523_.m_8055_(blockpos);
+       if (p_55526_) {
+          boolean flag = this.m_55612_(p_55523_, blockpos, blockstate);
+-         if (flag && m_55640_(p_55523_.m_8055_(blockpos.m_7494_()))) {
++         if (flag && p_55523_.m_8055_(blockpos.m_7494_()).canRedstoneConnectTo(p_55523_, blockpos.m_7494_(), null)) {
+             if (blockstate.m_60783_(p_55523_, blockpos, p_55525_.m_122424_())) {
+                return RedstoneSide.UP;
+             }
+@@ -208,7 +_,14 @@
+          }
+       }
+ 
+-      return !m_55594_(blockstate, p_55525_) && (blockstate.m_60796_(p_55523_, blockpos) || !m_55640_(p_55523_.m_8055_(blockpos.m_7495_()))) ? RedstoneSide.NONE : RedstoneSide.SIDE;
++      if (blockstate.canRedstoneConnectTo(p_55523_, blockpos, p_55525_)) {
++          return RedstoneSide.SIDE;
++      } else if (blockstate.m_60796_(p_55523_, blockpos)) {
++          return RedstoneSide.NONE;
++      } else {
++          BlockPos blockPosBelow = blockpos.m_7495_();
++          return p_55523_.m_8055_(blockPosBelow).canRedstoneConnectTo(p_55523_, blockPosBelow, null) ? RedstoneSide.SIDE : RedstoneSide.NONE;
++      }
+    }
+ 
+    public boolean m_7898_(BlockState p_55585_, LevelReader p_55586_, BlockPos p_55587_) {

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

@@ -719,4 +719,54 @@ public interface IForgeBlock
     {
         return state.is(Blocks.SCAFFOLDING);
     }
+
+    /**
+     * Whether redstone dust should visually connect to this block on a given side
+     * <p>
+     * The default implementation is identical to
+     * {@link RedStoneWireBlock#shouldConnectTo(BlockState, Direction)}
+     *
+     * <p>
+     * {@link RedStoneWireBlock} updates its visual connection when
+     * {@link BlockState#updateShape(Direction, BlockState, LevelAccessor, BlockPos, BlockPos)}
+     * is called, this callback is used during the evaluation of its new shape.
+     *
+     * @param state The current state
+     * @param world The world
+     * @param pos The block position in world
+     * @param direction The coming direction of the redstone dust connection (with respect to the block at pos)
+     * @return True if redstone dust should visually connect on the side passed
+     * <p>
+     * If the return value is evaluated based on world and pos (e.g. from BlockEntity), then the implementation of
+     * this block should notify its neighbors to update their shapes when necessary. Consider using
+     * {@link BlockState#updateNeighbourShapes(LevelAccessor, BlockPos, int, int)} or
+     * {@link BlockState#updateShape(Direction, BlockState, LevelAccessor, BlockPos, BlockPos)}.
+     * <p>
+     * Example:
+     * <p>
+     * 1. {@code yourBlockState.updateNeighbourShapes(world, yourBlockPos, UPDATE_ALL);}
+     * <p>
+     * 2. {@code neighborState.updateShape(fromDirection, stateOfYourBlock, world, neighborBlockPos, yourBlockPos)},
+     * where {@code fromDirection} is defined from the neighbor block's point of view.
+     */
+    default boolean canConnectRedstone(BlockState state, BlockGetter world, BlockPos pos, @Nullable Direction direction)
+    {
+        if (state.is(Blocks.REDSTONE_WIRE))
+        {
+            return true;
+        }
+        else if (state.is(Blocks.REPEATER))
+        {
+            Direction facing = state.getValue(RepeaterBlock.FACING);
+            return facing == direction || facing.getOpposite() == direction;
+        }
+        else if (state.is(Blocks.OBSERVER))
+        {
+            return direction == state.getValue(ObserverBlock.FACING);
+        }
+        else
+        {
+            return state.isSignalSource() && direction != null;
+        }
+    }
 }

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

@@ -641,4 +641,19 @@ public interface IForgeBlockState
     {
         return self().getBlock().isScaffolding(self(), entity.level, entity.blockPosition(), entity);
     }
+
+    /**
+     * Whether redstone dust should visually connect to this block on a side.
+     * <p>
+     * Modded redstone wire blocks should call this function to determine visual connections.
+     *
+     * @param world The world
+     * @param pos The block position in world
+     * @param direction The coming direction of the redstone dust connection (with respect to the block at pos)
+     * @return True if redstone dust should visually connect on the side passed
+     */
+    default boolean canRedstoneConnectTo(BlockGetter world, BlockPos pos, @Nullable Direction direction)
+    {
+        return self().getBlock().canConnectRedstone(self(), world, pos, direction);
+    }
 }

src/test/java/net/minecraftforge/debug/block/RedstoneSidedConnectivityTest.java

@@ -0,0 +1,97 @@
+/*
+ * Minecraft Forge
+ * Copyright (c) 2016-2021.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+package net.minecraftforge.debug.block;
+
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Direction;
+import net.minecraft.world.item.BlockItem;
+import net.minecraft.world.item.CreativeModeTab;
+import net.minecraft.world.item.Item;
+import net.minecraft.world.level.BlockGetter;
+import net.minecraft.world.level.Level;
+import net.minecraft.world.level.block.Block;
+import net.minecraft.world.level.block.entity.FurnaceBlockEntity;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.material.Material;
+import net.minecraftforge.eventbus.api.IEventBus;
+import net.minecraftforge.fml.common.Mod;
+import net.minecraftforge.fml.javafmlmod.FMLJavaModLoadingContext;
+import net.minecraftforge.fmllegacy.RegistryObject;
+import net.minecraftforge.registries.DeferredRegister;
+import net.minecraftforge.registries.ForgeRegistries;
+
+import javax.annotation.Nullable;
+
+@Mod(RedstoneSidedConnectivityTest.MODID)
+public class RedstoneSidedConnectivityTest
+{
+    public static final boolean ENABLE = true;
+    static final String MODID = "redstone_sided_connectivity_test";
+    static final String BLOCK_ID = "test_east_redstone_connect";
+
+    private static final DeferredRegister<Block> BLOCKS = DeferredRegister.create(ForgeRegistries.BLOCKS, MODID);
+    private static final DeferredRegister<Item> ITEMS = DeferredRegister.create(ForgeRegistries.ITEMS, MODID);
+
+    private static final RegistryObject<Block> TEST_REDSTONE_BLOCK = BLOCKS.register(BLOCK_ID, EastRedstoneBlock::new);
+    private static final RegistryObject<Item> TEST_REDSTONE_BLOCKITEM = ITEMS.register(BLOCK_ID,  () -> new BlockItem(TEST_REDSTONE_BLOCK.get(), new Item.Properties().tab(CreativeModeTab.TAB_BUILDING_BLOCKS)));
+
+    public RedstoneSidedConnectivityTest()
+    {
+        if (!ENABLE)
+            return;
+
+        IEventBus modBus = FMLJavaModLoadingContext.get().getModEventBus();
+        BLOCKS.register(modBus);
+        ITEMS.register(modBus);
+    }
+
+    private static class EastRedstoneBlock extends Block
+    {
+        //This block visually connect to redstone dust only on the east side
+        //if a furnace block is placed on top of it
+
+        public EastRedstoneBlock()
+        {
+            super(Properties.of(Material.METAL));
+        }
+
+        @Override
+        public boolean canConnectRedstone(BlockState state, BlockGetter world, BlockPos pos, @Nullable Direction direction)
+        {
+            //The passed direction is relative to the redstone dust
+            //This block connects on the east side relative to this block, which is west for the dust
+            return direction == Direction.WEST &&
+                    world.getBlockEntity(pos.relative(Direction.UP)) instanceof FurnaceBlockEntity;
+        }
+
+        @SuppressWarnings("deprecation")
+        @Override
+        public void neighborChanged(BlockState state, Level world, BlockPos pos, Block block, BlockPos fromPos, boolean isMoving)
+        {
+            if (pos.relative(Direction.UP).equals(fromPos))
+            {
+                //Notify neighbors if the redstone connection may change
+                state.updateNeighbourShapes(world, pos, UPDATE_ALL);
+            }
+
+            super.neighborChanged(state, world, pos, block, fromPos, isMoving);
+        }
+    }
+}

src/test/resources/META-INF/mods.toml

@@ -148,6 +148,8 @@ license="LGPL v2.1"
     modId="tag_based_tool_types"
 [[mods]]
     modId="check_spawn_event_test"
+[[mods]]
+    modId="redstone_sided_connectivity_test"
 [[mods]]
     modId="permissions_changed_event_test"
 [[mods]]

src/test/resources/assets/redstone_sided_connectivity_test/blockstates/test_east_redstone_connect.json

@@ -0,0 +1,7 @@
+{
+  "variants": {
+    "": {
+      "model": "redstone_sided_connectivity_test:block/test_east_redstone_connect"
+    }
+  }
+}

src/test/resources/assets/redstone_sided_connectivity_test/lang/en_us.json

@@ -0,0 +1,3 @@
+{
+  "block.redstone_sided_connectivity_test.test_east_redstone_connect": "Redstone Connector on East Only If Furnace on Top"
+}

src/test/resources/assets/redstone_sided_connectivity_test/models/block/test_east_redstone_connect.json

@@ -0,0 +1,12 @@
+{
+  "parent": "minecraft:block/cube",
+  "textures": {
+    "up": "minecraft:block/observer_front",
+    "down": "minecraft:block/furnace_side",
+    "north": "minecraft:block/furnace_side",
+    "east": "minecraft:block/observer_back",
+    "south": "minecraft:block/furnace_side",
+    "west": "minecraft:block/furnace_side",
+    "particle": "minecraft:block/observer_front"
+  }
+}

src/test/resources/assets/redstone_sided_connectivity_test/models/item/test_east_redstone_connect.json

@@ -0,0 +1,3 @@
+{
+  "parent": "redstone_sided_connectivity_test:block/test_east_redstone_connect"
+}