mapsyncer-paper 0.2.0: Paper 26.3

Build against the 26.3 dev bundle (26.3.build.151-beta; no stable build
exists yet).

26.3 rewrote the block palette in region files: a default-state block is a
bare string, any other state is {id, properties}, and a list mixing both
wraps the strings as {"": name}. The parser cast every entry to a
compound with Name/Properties, so every chunk saved by 26.3 threw
ClassCastException and the whole region failed to render. Both formats are
read now (a region holds a mix until every chunk is re-saved), and a chunk
that fails to parse is skipped instead of aborting the region.

NOTICE.md

@@ -28,6 +28,11 @@ diffs stay readable:
 - `mca/ChunkDataParser.java` — heightmap bit width uses vanilla's
   `ceillog2(height + 1)` (upstream under-counts by one for 256-high
   dimensions); accepted chunk statuses include `initialize_light`.
+- `mca/ChunkSectionParser.java` — reads the 26.3 block palette format (bare
+  string entries, `{id, properties}`, `{"": name}`) alongside the old
+  `{Name, Properties}` one. Same approach as upstream PR #26.
+- `mca/convert/io/McaRegionLoader.java` — a chunk that fails to parse is
+  skipped instead of aborting the region.
 - `XaeroWriter.java` — moved from `com.mapsyncer.server` to `com.mapsyncer`.
 - `render/BlockPropertyResolver.java`, `render/PlaceholderBlockGetter.java` —
   package moved; the cache-size constant is inlined.

README.md

@@ -37,7 +37,7 @@ Two visibility modes (`config.yml`):
 
 ## Requirements
 
-- Paper 26.2 on Java 25 (the build compiles against Paper's Mojang-mapped
+- Paper 26.3 on Java 25 (the build compiles against Paper's Mojang-mapped
   internals via paperweight; other versions need a rebuild).
 - Clients: Xaero's World Map 1.40.11+ and the MapSyncer client mod for the
   same Minecraft version.

gradle.properties

@@ -1,11 +1,11 @@
 group = lv.janhouse
-version = 0.1.0
+version = 0.2.0
 
 # Paper dev bundle (Mojang-mapped server + API) the plugin compiles against.
-# Must match the server it is deployed on: Paper 26.2 on JDK 25. The renderer
+# Must match the server it is deployed on: Paper 26.3 on JDK 25. The renderer
 # needs a handful of server internals (block classes, render shape, tags), which
 # is why this is a dev bundle and not plain paper-api.
-paperDevBundleVersion = 26.2.build.121-stable
+paperDevBundleVersion = 26.3.build.151-beta
 
 # Class-file target. The server container runs OpenJDK 25, so the jar must not
 # be compiled for anything newer; --release also fences off newer JDK APIs.

src/main/java/com/mapsyncer/mca/ChunkSectionParser.java

@@ -263,8 +263,7 @@ public class ChunkSectionParser {
             if (blockStates.contains("palette", Tag.TAG_LIST)) {
                 Tag.ListTag paletteList = blockStates.getList("palette", Tag.TAG_COMPOUND);
                 for (int i = 0; i < paletteList.items().size(); i++) {
-                    Tag.Compound stateTag = (Tag.Compound) paletteList.items().get(i);
+                    BlockState blockState = parsePaletteEntry(paletteList.items().get(i));
-                    BlockState blockState = parseBlockState(stateTag);
                     blockPalette.add(blockState);
                     blockNames.add(blockState.name());
                 }
@@ -345,22 +344,57 @@ public class ChunkSectionParser {
         );
     }
 
+    /**
+     * One {@code block_states.palette} entry, in any of the shapes a region file
+     * can hold.
+     *
+     * <p>Up to 26.2 every entry is {@code {Name: "...", Properties: {...}}}. From
+     * 26.3 a block in its default state is written as a bare string
+     * ({@code "minecraft:stone"}) and any other state as
+     * {@code {id: "...", properties: {...}}}; a list mixing both shapes has to be
+     * all compounds, so the bare strings are wrapped as {@code {"": "..."}}.
+     * A region keeps chunks in both formats until every chunk has been re-saved,
+     * so the old shape stays supported. No properties means the default state,
+     * which is also how Xaero reads a state written without them.</p>
+     */
+    private static BlockState parsePaletteEntry(Tag entry) {
+        if (entry instanceof Tag.StringTag str) {
+            return new BlockState(str.value(), BlockState.EMPTY_PROPERTIES);
+        }
+        if (entry instanceof Tag.Compound compound) {
+            return parseBlockState(compound);
+        }
+        // Keeps palette indices aligned with the data array.
+        return new BlockState("minecraft:air", BlockState.EMPTY_PROPERTIES);
+    }
+
     /**
      * 解析单个方块状态的NBT
      *
-     * <p>格式: {Name: "minecraft:grass_block", Properties: {snowy: "false"}}</p>
+     * <p>格式: {Name: "minecraft:grass_block", Properties: {snowy: "false"}}
+     * (26.3+: {@code id} / {@code properties}, or {@code ""} for a wrapped bare name)</p>
      *
      * @param stateTag 方块状态的NBT复合标签
      * @return 解析后的BlockState对象
      */
     private static BlockState parseBlockState(Tag.Compound stateTag) {
         String name = stateTag.getString("Name");
+        if (name.isEmpty()) {
+            name = stateTag.getString("id");
+        }
+        if (name.isEmpty()) {
+            name = stateTag.getString("");
+        }
+        if (name.isEmpty()) {
+            name = "minecraft:air";
+        }
 
-        if (!stateTag.contains("Properties", Tag.TAG_COMPOUND)) {
+        String propsKey = stateTag.contains("Properties", Tag.TAG_COMPOUND) ? "Properties" : "properties";
+        if (!stateTag.contains(propsKey, Tag.TAG_COMPOUND)) {
             return new BlockState(name, BlockState.EMPTY_PROPERTIES);
         }
 
-        Tag.Compound propsTag = stateTag.getCompound("Properties");
+        Tag.Compound propsTag = stateTag.getCompound(propsKey);
         if (propsTag.children().isEmpty()) {
             return new BlockState(name, BlockState.EMPTY_PROPERTIES);
         }

src/main/java/com/mapsyncer/mca/convert/io/McaRegionLoader.java

@@ -136,7 +136,12 @@ public final class McaRegionLoader {
                 if (nbt == null) {
                     continue;
                 }
-                grid[localX][localZ] = ChunkDataParser.parseChunk(localX, localZ, nbt, worldHeightRange);
+                try {
+                    grid[localX][localZ] = ChunkDataParser.parseChunk(localX, localZ, nbt, worldHeightRange);
+                } catch (RuntimeException e) {
+                    // One malformed chunk must not cost the whole region.
+                    LOGGER.warn("Failed to parse chunk ({}, {}), skipping: {}", localX, localZ, e.toString());
+                }
             }
         }
         return grid;

src/main/java/lv/janhouse/mapsyncer/Settings.java

@@ -34,8 +34,6 @@ public final class Settings {
     public final int clientPollIntervalTicks;
     public final int helloDelayTicks;
 
-    public final String serverName;
-
     public final WorldSettings defaultWorld;
     public final Map<String, WorldSettings> worlds;
 
@@ -66,7 +64,9 @@ public final class Settings {
         clientPollIntervalTicks = clamp(c.getInt("sync.client-poll-interval-ticks", 6000), 1200, 72000, "sync.client-poll-interval-ticks", warn);
         helloDelayTicks = clamp(c.getInt("sync.hello-delay-ticks", 100), 1, 1200, "sync.hello-delay-ticks", warn);
 
-        serverName = c.getString("server-name", "");
+        if (c.contains("server-name")) {
+            warn.accept("server-name is ignored: the released MapSyncer client cannot read that hello field.");
+        }
 
         ConfigurationSection ws = c.getConfigurationSection("worlds");
         WorldSettings def = new WorldSettings(true, TrackedWorld.Layers.AUTO);

src/main/java/lv/janhouse/mapsyncer/net/Protocol.java

@@ -74,16 +74,20 @@ public final class Protocol {
 
     // -------------------------------------------------------------- encoders
 
+    /**
+     * Five fields, no more. Upstream's git HEAD appends a sixth (serverName), but
+     * the released 1.0.4 client reads exactly five and vanilla disconnects on
+     * "8 bytes extra" if anything follows — verified against the shipped jar.
+     */
     public static byte[] encodeServerInstalled(String version, long lastGenerationTimestamp,
                                                int autoSyncIntervalMinutes, UpdateMode mode,
-                                               int incrementalUpdateIntervalTicks, String serverName) {
+                                               int incrementalUpdateIntervalTicks) {
         return new PacketWriter(64)
                 .writeUtf(version)
                 .writeLong(lastGenerationTimestamp)
                 .writeInt(autoSyncIntervalMinutes)
                 .writeByte(mode.ordinal())
                 .writeInt(incrementalUpdateIntervalTicks)
-                .writeUtf(serverName == null ? "" : serverName)
                 .toByteArray();
     }
 

src/main/java/lv/janhouse/mapsyncer/net/SyncService.java

@@ -199,7 +199,7 @@ public final class SyncService implements PluginMessageListener, Listener {
         int minutes = Math.max(1, ticks / 20 / 60);
         byte[] payload = Protocol.encodeServerInstalled(
                 "mapsyncer-paper/" + plugin.getPluginMeta().getVersion(),
-                lastGen, minutes, Protocol.UpdateMode.TICK, ticks, settings.serverName);
+                lastGen, minutes, Protocol.UpdateMode.TICK, ticks);
         player.sendPluginMessage(plugin, Protocol.SERVER_INSTALLED, payload);
         s.helloSent = true;
         helloCount.incrementAndGet();

src/main/resources/config.yml

@@ -58,10 +58,6 @@ sync:
   # cache, otherwise it forgets what it already has and re-syncs on every join.
   hello-delay-ticks: 100
 
-# Optional stable name sent to clients. The client mod uses it to recognise this
-# server when it is reached under a different address. Leave empty to disable.
-server-name: ""
-
 # Per-world settings. Keys are Bukkit world names. Anything not listed uses
 # "default". `layers` controls what is rendered:
 #   auto     surface for worlds with a sky, cave layers for worlds with a ceiling

src/test/java/com/mapsyncer/mca/ChunkSectionParserTest.java

@@ -0,0 +1,58 @@
+package com.mapsyncer.mca;
+
+import com.mapsyncer.nbt.Tag;
+import org.junit.jupiter.api.Test;
+
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+/** Palette shapes as written by 26.2 and 26.3 servers (DataVersion 4790 / 5023). */
+class ChunkSectionParserTest {
+
+    @Test
+    void readsPre263Compounds() {
+        var section = parse(List.of(
+                compound(Map.of("Name", str("minecraft:stone"))),
+                compound(Map.of("Name", str("minecraft:oak_log"),
+                        "Properties", compound(Map.of("axis", str("x")))))));
+        assertEquals(List.of("minecraft:stone", "minecraft:oak_log"), section.blockNames());
+        assertEquals(Map.of("axis", "x"), section.blockPalette().get(1).properties());
+    }
+
+    @Test
+    void readsBareStrings() {
+        var section = parse(List.of(str("minecraft:bedrock"), str("minecraft:deepslate")));
+        assertEquals(List.of("minecraft:bedrock", "minecraft:deepslate"), section.blockNames());
+        assertEquals(Map.of(), section.blockPalette().get(1).properties());
+    }
+
+    @Test
+    void readsMixed263Compounds() {
+        var section = parse(List.of(
+                compound(Map.of("", str("minecraft:deepslate"))),
+                compound(Map.of("id", str("minecraft:pointed_dripstone"),
+                        "properties", compound(Map.of("vertical_direction", str("down")))))));
+        assertEquals(List.of("minecraft:deepslate", "minecraft:pointed_dripstone"), section.blockNames());
+        assertEquals(Map.of("vertical_direction", "down"), section.blockPalette().get(1).properties());
+    }
+
+    private static ChunkSectionParser.SectionData parse(List<Tag> palette) {
+        Map<String, Tag> blockStates = new LinkedHashMap<>();
+        blockStates.put("palette", new Tag.ListTag("palette", Tag.TAG_COMPOUND, palette));
+        Map<String, Tag> section = new LinkedHashMap<>();
+        section.put("Y", new Tag.Byte("Y", (byte) 0));
+        section.put("block_states", new Tag.Compound("block_states", blockStates));
+        return ChunkSectionParser.parseSection(new Tag.Compound("", section));
+    }
+
+    private static Tag.StringTag str(String value) {
+        return new Tag.StringTag("", value);
+    }
+
+    private static Tag.Compound compound(Map<String, Tag> children) {
+        return new Tag.Compound("", children);
+    }
+}

src/test/java/lv/janhouse/mapsyncer/net/ProtocolTest.java

@@ -138,6 +138,20 @@ class ProtocolTest {
         assertFalse(Protocol.split(0, 0, "null", new byte[100], 1, Protocol.SURFACE_LAYER).get(0).isSplit());
     }
 
+    @Test
+    void helloHasExactlyFiveFields() {
+        // The released 1.0.4 client reads utf, long, int, byte, int and nothing
+        // else; a trailing byte disconnects the player.
+        byte[] hello = Protocol.encodeServerInstalled("v", 123L, 5, Protocol.UpdateMode.TICK, 6000);
+        PacketReader r = new PacketReader(hello);
+        assertEquals("v", r.readUtf());
+        assertEquals(123L, r.readLong());
+        assertEquals(5, r.readInt());
+        assertEquals(1, r.readByte());
+        assertEquals(6000, r.readInt());
+        assertEquals(0, r.readableBytes());
+    }
+
     @Test
     void hashValidity() {
         assertTrue(Protocol.isValidHash("a1b2c3d4"));