fix: preserve virtual multipart tile accessors

src/test/java/codechicken/multipart/TMultiPartTileAccessorRegressionTest.java

@@ -0,0 +1,142 @@
+package codechicken.multipart;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+import java.io.ByteArrayOutputStream;
+import java.io.DataOutputStream;
+
+import net.minecraft.block.Block;
+import net.minecraft.util.Vec3;
+import net.minecraft.world.World;
+
+import org.junit.jupiter.api.Test;
+
+import codechicken.lib.data.MCDataInput;
+import codechicken.lib.data.MCDataOutput;
+import codechicken.lib.data.MCDataOutputWrapper;
+
+class TMultiPartTileAccessorRegressionTest {
+
+    @Test
+    void bindingUsesTheOverriddenSetterIncludingUnbinding() {
+        VirtualPart part = new VirtualPart();
+        RecordingTile tile = new RecordingTile();
+
+        part.bind(tile);
+        assertSame(tile, part.current);
+        assertEquals(1, part.binds);
+        part.bind(null);
+        assertNull(part.current);
+        assertEquals(2, part.binds);
+    }
+
+    @Test
+    void convenienceMethodsUseTheTileSuppliedByTheOverride() {
+        VirtualPart part = new VirtualPart();
+        RecordingTile tile = new RecordingTile();
+        part.current = tile;
+        tile.xCoord = 42;
+        tile.yCoord = 73;
+        tile.zCoord = -4;
+
+        assertSame(tile, part.getTile());
+        assertEquals(42, part.x());
+        assertEquals(73, part.y());
+        assertEquals(-4, part.z());
+        assertNull(part.world());
+        assertEquals(1, tile.worldReads);
+        assertSame(tile.stream, part.getWriteStream());
+        assertSame(part, tile.streamPart);
+        assertNull(part.collisionRayTrace(Vec3.createVectorHelper(0, 0, 0), Vec3.createVectorHelper(1, 1, 1)));
+        assertEquals(1, tile.blockReads);
+    }
+
+    @Test
+    void descriptionUpdatesFollowTheTilePublishedByReadDescAndSkipAnUnboundPart() {
+        VirtualPart part = new VirtualPart();
+        RecordingTile original = new RecordingTile();
+        RecordingTile replacement = new RecordingTile();
+        part.current = original;
+        part.onRead = () -> part.current = replacement;
+
+        part.read(null);
+        assertEquals(0, original.renderUpdates);
+        assertEquals(1, replacement.renderUpdates);
+        part.sendDescUpdate();
+        assertEquals(0, original.bytes.size());
+        assertArrayEquals(new byte[] { 7 }, replacement.bytes.toByteArray());
+
+        part.current = null;
+        assertNull(part.world());
+        part.sendDescUpdate();
+        assertEquals(1, part.descriptionsWritten);
+    }
+
+    private static final class VirtualPart extends TMultiPart {
+
+        TileMultipart current;
+        int binds;
+        int descriptionsWritten;
+        Runnable onRead;
+
+        @Override
+        public String getType() {
+            return "test:virtual-tile";
+        }
+
+        @Override
+        public TileMultipart tile() {
+            return current;
+        }
+
+        @Override
+        public void tile_$eq(TileMultipart value) {
+            binds++;
+            current = value;
+        }
+
+        @Override
+        public void readDesc(MCDataInput packet) {
+            onRead.run();
+        }
+
+        @Override
+        public void writeDesc(MCDataOutput packet) {
+            descriptionsWritten++;
+            packet.writeByte(7);
+        }
+    }
+
+    private static final class RecordingTile extends TileMultipart {
+
+        final ByteArrayOutputStream bytes = new ByteArrayOutputStream();
+        final MCDataOutput stream = new MCDataOutputWrapper(new DataOutputStream(bytes));
+        TMultiPart streamPart;
+        int worldReads;
+        int blockReads;
+        int renderUpdates;
+
+        @Override
+        public World getWorldObj() {
+            worldReads++;
+            return null;
+        }
+
+        @Override
+        public Block getBlockType() {
+            blockReads++;
+            return null;
+        }
+
+        @Override
+        public MCDataOutput getWriteStream(TMultiPart part) {
+            streamPart = part;
+            return stream;
+        }
+
+        @Override
+        public void markRender() {
+            renderUpdates++;
+        }
+    }
+}