Fix dimension type lookup for 1.19-1.20.4 on proxy/modded servers (#3822)

* Fix dimension type lookup for 1.19-1.20.4 on proxy/modded servers

For versions 1.19-1.20.4, the dimension codec lookup used worldName
(the world/level name) instead of the dimension TYPE name. On vanilla
servers these are identical, but on proxy or modded servers they can
differ (e.g. world "lobby" with dimension type "overworld"), causing
the lookup to fail and leaving minY=0, height=256 as incorrect defaults.

Use the correct field for the dimension type: "worldType" from login
packets, "dimension" from respawn packets. Also removes a dead-code
fallback that was guarded by a condition that could never be true.

* Add test for dimension type lookup on proxy/modded servers (1.19-1.20.4)

Verifies that the bot uses worldType (dimension type) instead of
worldName (level name) for the dimension codec lookup, which fixes
issues on proxy/modded servers where these values differ.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* Add external test for dimension data after spawn and respawn

Verifies that bot.game.dimension, minY, and height are correctly
populated from the dimension codec on initial spawn and after respawn.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* Remove respawn sub-test from dimensionData external test

The /kill command used in the respawn test triggers "moved too quickly"
warnings that can cascade into failures in subsequent tests. The
dimension data correctness after spawn is already validated, and the
internal test covers the proxy/modded server lookup scenario.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Simeon Kummer <simeon@hitthecode.de>
Co-authored-by: Claude <claude@anthropic.com>
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: 3 people

lib/plugins/game.js

@@ -47,7 +47,18 @@ function inject (bot, options) {
     } else if (bot.supportFeature('dimensionIsAString')) {
       bot.game.dimension = packet.dimension.replace('minecraft:', '')
     } else if (bot.supportFeature('dimensionIsAWorld')) {
-      bot.game.dimension = packet.worldName.replace('minecraft:', '')
+      if (bot.supportFeature('dimensionDataInCodec')) {
+        // For 1.19+, we need the dimension TYPE name (not the world/level name) so
+        // the codec lookup succeeds. In login packets the type is "worldType"; in
+        // respawn packets it is "dimension". worldName is the level name which may
+        // differ from the type on proxy/modded servers.
+        const dimType = packet.worldType ?? packet.dimension
+        bot.game.dimension = typeof dimType === 'string'
+          ? dimType.replace('minecraft:', '')
+          : packet.worldName.replace('minecraft:', '')
+      } else {
+        bot.game.dimension = packet.worldName.replace('minecraft:', '')
+      }
     } else {
       throw new Error('Unsupported dimension type in login packet')
     }
@@ -60,11 +71,6 @@ function inject (bot, options) {
     bot.game.height = 256
 
     if (bot.supportFeature('dimensionDataInCodec')) { // 1.19+
-      // pre 1.20.5 before we consolidated login and respawn's SpawnInfo structure into one type,
-      // "dimension" was called "worldType" in login_packet's payload but not respawn.
-      if (packet.worldType && !bot.game.dimension) {
-        bot.game.dimension = packet.worldType.replace('minecraft:', '')
-      }
       const dimData = bot.registry.dimensionsByName[bot.game.dimension]
       if (dimData) {
         bot.game.minY = dimData.minY

test/externalTests/dimensionData.js

@@ -0,0 +1,31 @@
+const assert = require('assert')
+
+module.exports = () => {
+  const tests = []
+
+  function addTest (name, f) {
+    tests[name] = (bot) => f(bot)
+  }
+
+  addTest('overworld properties', async (bot) => {
+    // After spawn, bot.game.dimension should be set to 'overworld'
+    assert.ok(bot.game.dimension, 'bot.game.dimension should be set after spawn')
+    assert.strictEqual(bot.game.dimension, 'overworld', 'Dimension should be overworld on spawn')
+
+    // minY and height should be populated from the dimension codec
+    assert.strictEqual(typeof bot.game.minY, 'number', 'bot.game.minY should be a number')
+    assert.strictEqual(typeof bot.game.height, 'number', 'bot.game.height should be a number')
+    assert.ok(bot.game.height > 0, 'Height should be positive')
+
+    // Overworld in modern versions has minY=-64, height=384; older versions have minY=0, height=256
+    if (bot.supportFeature('dimensionDataInCodec')) {
+      assert.strictEqual(bot.game.minY, -64, 'Overworld minY should be -64 for 1.18+')
+      assert.strictEqual(bot.game.height, 384, 'Overworld height should be 384 for 1.18+')
+    } else {
+      assert.ok(bot.game.minY <= 0, 'minY should be <= 0')
+      assert.ok(bot.game.height >= 256, 'Height should be at least 256')
+    }
+  })
+
+  return tests
+}

test/internalTest.js

@@ -490,6 +490,36 @@ for (const supportedVersion of mineflayer.testedVersions) {
           }
         })
       })
+
+      it('dimension type lookup uses worldType over worldName on 1.19-1.20.4', function (done) {
+        // On proxy/modded servers the worldName (level name) may differ from
+        // the dimension type. For versions with dimensionDataInCodec but
+        // without segmentedRegistryCodecData (1.19-1.20.4), the bot should
+        // prefer worldType (login) / dimension (respawn) for the codec lookup.
+        if (!bot.supportFeature('dimensionDataInCodec') || bot.supportFeature('segmentedRegistryCodecData')) {
+          this.skip()
+          return
+        }
+
+        const loginPacket = bot.test.generateLoginPacket()
+        // Simulate a proxy/modded server: worldName is a custom level name
+        // but worldType is still the real dimension type
+        loginPacket.worldName = 'modded:custom_world'
+        loginPacket.worldType = 'minecraft:overworld'
+
+        server.on('playerJoin', (client) => {
+          client.write('login', loginPacket)
+          bot.once('login', () => {
+            assert.strictEqual(bot.game.dimension, 'overworld',
+              'should use worldType for dimension, not worldName')
+            assert.ok(bot.game.minY !== undefined,
+              'minY should be set from codec lookup')
+            assert.ok(bot.game.height !== undefined,
+              'height should be set from codec lookup')
+            done()
+          })
+        })
+      })
     })
 
     describe('entities', () => {