Replace assert with proper null checks for content in write method

src/main/java/net/minestom/server/collision/CollisionUtils.java

@@ -35,7 +35,9 @@ public final class CollisionUtils {
     public static PhysicsResult handlePhysics(@NotNull Entity entity, @NotNull Vec entityVelocity,
                                               @Nullable PhysicsResult lastPhysicsResult, boolean singleCollision) {
         final Instance instance = entity.getInstance();
-        assert instance != null;
+        if (instance == null) {
+            throw new IllegalStateException("Instance cannot be null for entity: " + entity);
+        }
         return handlePhysics(instance, entity.getChunk(),
                 entity.getBoundingBox(),
                 entity.getPosition(), entityVelocity,
@@ -83,7 +85,9 @@ public static PhysicsResult handlePhysics(@NotNull Entity entity, @NotNull Vec e
     public static PhysicsResult handlePhysics(@NotNull Entity entity, @NotNull Vec entityVelocity,
                                               @Nullable PhysicsResult lastPhysicsResult) {
         final Instance instance = entity.getInstance();
-        assert instance != null;
+        if (instance == null) {
+            throw new IllegalStateException("Instance cannot be null for entity: " + entity);
+        }
         return handlePhysics(instance, entity.getChunk(),
                 entity.getBoundingBox(),
                 entity.getPosition(), entityVelocity,

src/main/java/net/minestom/server/collision/ShapeImpl.java

@@ -175,9 +175,9 @@ private static BoundingBox[] parseRegistryBoundingBoxString(String str) {
             final Vec min = new Vec(minX, minY, minZ);
             final Vec max = new Vec(minX + boundXSize, minY + boundYSize, minZ + boundZSize);
             final BoundingBox bb = new BoundingBox(min, max);
-            assert bb.minX() == minX;
-            assert bb.minY() == minY;
-            assert bb.minZ() == minZ;
+            if (bb.minX() != minX || bb.minY() != minY || bb.minZ() != minZ) {
+                throw new IllegalStateException("BoundingBox min values do not match the parsed values.");
+            }
             boundingBoxes[i] = bb;
         }
         return boundingBoxes;

src/main/java/net/minestom/server/command/CommandParserImpl.java

@@ -407,7 +407,9 @@ int cursor() {
         }
 
         void cursor(int cursor) {
-            assert cursor >= 0 && cursor <= input.length();
+            if (cursor < 0 || cursor > input.length()) {
+                throw new IllegalArgumentException("Cursor value must be between 0 and the length of the input.");
+            }
             this.cursor = cursor;
         }
     }
@@ -431,7 +433,9 @@ private static <T> ArgumentResult<T> parseArgument(@NotNull CommandSender sender
             return new ArgumentResult.IncompatibleType<>();
         }
         // Bruteforce
-        assert argument.allowSpace() && !argument.useRemaining();
+        if (!(argument.allowSpace() && !argument.useRemaining())) {
+            throw new IllegalArgumentException("Argument must allow space and not use remaining.");
+        }
         StringBuilder current = new StringBuilder(reader.readWord());
         while (true) {
             try {

src/main/java/net/minestom/server/component/DataComponentMapImpl.java

@@ -150,7 +150,9 @@ public void write(@NotNull NetworkBuffer buffer, DataComponentMap value) {
                     buffer.write(NetworkBuffer.VAR_INT, entry.getIntKey());
                     //noinspection unchecked
                     DataComponent<Object> type = (DataComponent<Object>) this.idToType.apply(entry.getIntKey());
-                    assert type != null;
+                    if (type == null) {
+                        throw new IllegalStateException("DataComponent type cannot be null for key: " + entry.getIntKey());
+                    }
                     type.write(buffer, entry.getValue());
                 }
             }

src/main/java/net/minestom/server/entity/Entity.java

@@ -137,8 +137,9 @@ public void remove(@NotNull Entity entity) {
         @Override
         public void referenceUpdate(@NotNull Point point, @Nullable EntityTracker tracker) {
             final Instance currentInstance = tracker != null ? instance : null;
-            assert currentInstance == null || currentInstance.getEntityTracker() == tracker :
-                    "EntityTracker does not match current instance";
+            if (currentInstance != null && currentInstance.getEntityTracker() != tracker) {
+                throw new IllegalStateException("EntityTracker does not match current instance");
+            }
             viewEngine.updateTracker(currentInstance, point);
         }
     };
@@ -1237,7 +1238,9 @@ public void refreshPosition(@NotNull final Pos newPosition, boolean ignoreView,
         final boolean positionChange = (distanceX + distanceY + distanceZ) > 0;
 
         final Chunk chunk = getChunk();
-        assert chunk != null;
+        if (chunk == null) {
+            throw new IllegalStateException("Chunk cannot be null");
+        }
         if (distanceX > 8 || distanceY > 8 || distanceZ > 8) {
             PacketUtils.prepareViewablePacket(chunk, new EntityTeleportPacket(getEntityId(), position, isOnGround()), this);
             nextSynchronizationTick = synchronizationTicks + 1;
@@ -1306,7 +1309,9 @@ protected void refreshCoordinate(Point newPosition) {
         }
         // Handle chunk switch
         final Instance instance = getInstance();
-        assert instance != null;
+        if (instance == null) {
+            throw new IllegalStateException("Instance cannot be null");
+        }
         instance.getEntityTracker().move(this, newPosition, trackingTarget, trackingUpdate);
         final int lastChunkX = currentChunk.getChunkX();
         final int lastChunkZ = currentChunk.getChunkZ();

src/main/java/net/minestom/server/entity/EntityView.java

@@ -166,7 +166,9 @@ public boolean isRegistered(T entity) {
         }
 
         public void register(T entity) {
-            assert entity.getInstance() != null : "Instance-less entity shouldn't be registered as viewer";
+            if (entity.getInstance() == null) {
+                throw new IllegalArgumentException("Instance-less entity shouldn't be registered as viewer");
+            }
             this.bitSet.add(entity.getEntityId());
         }
 

src/main/java/net/minestom/server/entity/Player.java

@@ -678,7 +678,9 @@ public Void join() {
                         throw new RuntimeException(e);
                     }
                     scheduler.process();
-                    assert isDone();
+                    if (!isDone()) {
+                        throw new IllegalStateException("Future should be completed before processing.");
+                    }
                 }
                 return super.join();
             }

src/main/java/net/minestom/server/event/EventNodeImpl.java

@@ -276,7 +276,9 @@ record Graph(String name, String eventType, int priority,
     }
 
     void invalidateEventsFor(EventNodeImpl<? super T> node) {
-        assert Thread.holdsLock(GLOBAL_CHILD_LOCK);
+        if (!Thread.holdsLock(GLOBAL_CHILD_LOCK)) {
+            throw new IllegalStateException("Thread must hold the GLOBAL_CHILD_LOCK to call this method");
+        }
         for (Class<? extends T> eventType : listenerMap.keySet()) {
             node.invalidateEvent(eventType);
         }

src/main/java/net/minestom/server/event/trait/EntityInstanceEvent.java

@@ -14,7 +14,9 @@ public interface EntityInstanceEvent extends EntityEvent, InstanceEvent {
     @Override
     default @NotNull Instance getInstance() {
         final Instance instance = getEntity().getInstance();
-        assert instance != null : "EntityInstanceEvent is only supported on events where the entity's instance is non-null!";
+        if (instance == null) {
+            throw new IllegalStateException("EntityInstanceEvent is only supported on events where the entity's instance is non-null!");
+        }
         return instance;
     }
 }

src/main/java/net/minestom/server/instance/DynamicChunk.java

@@ -335,6 +335,8 @@ private void calculateFullHeightmap() {
     }
 
     private void assertLock() {
-        assert Thread.holdsLock(this) : "Chunk must be locked before access";
+        if (!Thread.holdsLock(this)) {
+            throw new IllegalStateException("Chunk must be locked before access");
+        }
     }
 }

src/main/java/net/minestom/server/instance/InstanceContainer.java

@@ -319,7 +319,9 @@ public Chunk getChunk(int chunkX, int chunkZ) {
 
                     EventDispatcher.call(new InstanceChunkLoadEvent(this, chunk));
                     final CompletableFuture<Chunk> future = this.loadingChunks.remove(index);
-                    assert future == completableFuture : "Invalid future: " + future;
+                    if (future != completableFuture) {
+                        throw new IllegalStateException("Invalid future: " + future);
+                    }
                     completableFuture.complete(chunk);
                 })
                 .exceptionally(throwable -> {

src/main/java/net/minestom/server/instance/anvil/AnvilLoader.java

@@ -147,7 +147,9 @@ public void loadInstance(@NotNull Instance instance) {
             perRegionLoadedChunksLock.lock();
             try {
                 Set<IntIntImmutablePair> previousVersion = perRegionLoadedChunks.put(new IntIntImmutablePair(regionX, regionZ), new HashSet<>());
-                assert previousVersion == null : "The AnvilLoader cache should not already have data for this region.";
+                if (previousVersion != null) {
+                    throw new IllegalStateException("The AnvilLoader cache should not already have data for this region.");
+                }
                 return new RegionFile(regionPath);
             } catch (IOException e) {
                 MinecraftServer.getExceptionManager().handleException(e);

src/main/java/net/minestom/server/instance/block/BlockImpl.java

@@ -70,7 +70,9 @@ static Collection<Block> values() {
     @Override
     public @NotNull Block withProperty(@NotNull String property, @NotNull String value) {
         final PropertyType[] propertyTypes = PROPERTIES_TYPE.get(id());
-        assert propertyTypes != null;
+        if (propertyTypes == null) {
+            throw new IllegalStateException("Property types cannot be null for id: " + id());
+        }
         final byte keyIndex = findKeyIndex(propertyTypes, property, this);
         final byte valueIndex = findValueIndex(propertyTypes[keyIndex], value, this);
         final long updatedProperties = updateIndex(propertiesArray, keyIndex, valueIndex);
@@ -81,7 +83,9 @@ static Collection<Block> values() {
     public @NotNull Block withProperties(@NotNull Map<@NotNull String, @NotNull String> properties) {
         if (properties.isEmpty()) return this;
         final PropertyType[] propertyTypes = PROPERTIES_TYPE.get(id());
-        assert propertyTypes != null;
+        if (propertyTypes == null) {
+            throw new IllegalStateException("Property types cannot be null for id: " + id());
+        }
         long updatedProperties = this.propertiesArray;
         for (Map.Entry<String, String> entry : properties.entrySet()) {
             final byte keyIndex = findKeyIndex(propertyTypes, entry.getKey(), this);
@@ -114,7 +118,9 @@ static Collection<Block> values() {
     @Override
     public @Unmodifiable @NotNull Map<String, String> properties() {
         final PropertyType[] propertyTypes = PROPERTIES_TYPE.get(id());
-        assert propertyTypes != null;
+        if (propertyTypes == null) {
+            throw new IllegalStateException("Property types cannot be null for id: " + id());
+        }
         final int length = propertyTypes.length;
         if (length == 0) return Map.of();
         String[] keys = new String[length];
@@ -167,7 +173,9 @@ public int hashCode() {
     private Block compute(long updatedProperties) {
         if (updatedProperties == this.propertiesArray) return this;
         final BlockImpl block = possibleProperties().get(updatedProperties);
-        assert block != null;
+        if (block == null) {
+            throw new IllegalStateException("Block cannot be null for updated properties: " + updatedProperties);
+        }
         // Reuse the same block instance if possible
         if (nbt == null && handler == null) return block;
         // Otherwise copy with the nbt and handler
@@ -192,7 +200,9 @@ private static Block createImpl(String namespace, Registry.Properties properties
                 for (var entry : stateProperties) {
                     final var k = entry.getKey();
                     final var v = (List<String>) entry.getValue();
-                    assert v.size() < MAX_VALUES;
+                    if (v.size() >= MAX_VALUES) {
+                        throw new IllegalStateException("Too many values for property " + k + " in block " + namespace);
+                    }
                     propertyTypes[i++] = new PropertyType(k, v);
                 }
             } else {
@@ -211,7 +221,9 @@ private static Block createImpl(String namespace, Registry.Properties properties
                 final String query = stateEntry.getKey();
                 final var stateOverride = (Map<String, Object>) stateEntry.getValue();
                 final var propertyMap = BlockUtils.parseProperties(query);
-                assert propertyTypes.length == propertyMap.size();
+                if (propertyTypes.length != propertyMap.size()) {
+                    throw new IllegalStateException("Property types size mismatch for query " + query);
+                }
                 long propertiesValue = 0;
                 for (Map.Entry<String, String> entry : propertyMap.entrySet()) {
                     final byte keyIndex = findKeyIndex(propertyTypes, entry.getKey(), null);

src/main/java/net/minestom/server/instance/generator/GeneratorImpl.java

@@ -105,10 +105,12 @@ static final class DynamicFork implements Block.Setter {
         public void setBlock(int x, int y, int z, @NotNull Block block) {
             resize(x, y, z);
             GenerationUnit section = findAbsolute(sections, minSection, width, height, depth, x, y, z);
-            assert section.absoluteStart().chunkX() == getChunkCoordinate(x) &&
+            boolean isValidSection = section.absoluteStart().chunkX() == getChunkCoordinate(x) &&
                     section.absoluteStart().section() == getChunkCoordinate(y) &&
-                    section.absoluteStart().chunkZ() == getChunkCoordinate(z) :
-                    "Invalid section " + section.absoluteStart() + " for " + x + ", " + y + ", " + z;
+                    section.absoluteStart().chunkZ() == getChunkCoordinate(z);
+            if (!isValidSection) {
+                throw new IllegalStateException("Invalid section " + section.absoluteStart() + " for coordinates (" + x + ", " + y + ", " + z + ")");
+            }
             section.modifier().setBlock(x, y, z, block);
         }
 
@@ -528,7 +530,9 @@ private static GenerationUnit findAbsolute(List<GenerationUnit> units, Point sta
 
     private static int findIndex(int width, int height, int depth,
                                  int x, int y, int z) {
-        assert width > 0 && height > 0 && depth > 0;
+        if (width <= 0 || height <= 0 || depth <= 0) {
+            throw new IllegalArgumentException("Dimensions (width, height, depth) must be positive");
+        }
         return (z * width * height) + (y * width) + x;
     }
 

src/main/java/net/minestom/server/instance/light/BlockLight.java

@@ -34,7 +34,9 @@ static ShortArrayFIFOQueue buildInternalQueue(Palette blockPalette) {
         // Apply section light
         blockPalette.getAllPresent((x, y, z, stateId) -> {
             final Block block = Block.fromStateId((short) stateId);
-            assert block != null;
+            if (block == null) {
+                throw new IllegalStateException("Block cannot be null for stateId: " + stateId);
+            }
             final byte lightEmission = (byte) block.registry().lightEmission();
 
             final int index = x | (z << 4) | (y << 8);

src/main/java/net/minestom/server/instance/palette/FlexiblePalette.java

@@ -138,7 +138,9 @@ public void setAll(@NotNull EntrySupplier supplier) {
                 }
             }
         }
-        assert index == maxSize();
+        if (index != maxSize()) {
+            throw new IllegalStateException("Index does not match the expected max size");
+        }
         // Update palette content
         if (fillValue < 0) {
             updateAll(cache);
@@ -167,7 +169,9 @@ public void replaceAll(@NotNull EntryFunction function) {
             cache[index] = newValue != value ? getPaletteIndex(newValue) : value;
             if (newValue != 0) count.setPlain(count.getPlain() + 1);
         });
-        assert arrayIndex.getPlain() == maxSize();
+        if (arrayIndex.getPlain() != maxSize()) {
+            throw new IllegalStateException("Array index does not match the expected max size");
+        }
         // Update palette content
         updateAll(cache);
         this.count = count.getPlain();
@@ -249,7 +253,9 @@ private void retrieveAll(@NotNull EntryConsumer consumer, boolean consumeEmpty)
 
     private void updateAll(int[] paletteValues) {
         final int size = maxSize();
-        assert paletteValues.length >= size;
+        if (paletteValues.length < size) {
+            throw new IllegalArgumentException("Palette values array length is smaller than the expected size");
+        }
         final int bitsPerEntry = this.bitsPerEntry;
         final int valuesPerLong = 64 / bitsPerEntry;
         final long clear = (1L << bitsPerEntry) - 1L;
@@ -274,7 +280,9 @@ void resize(byte newBitsPerEntry) {
         getAll(palette::set);
         this.bitsPerEntry = palette.bitsPerEntry;
         this.values = palette.values;
-        assert this.count == palette.count;
+        if (this.count != palette.count) {
+            throw new IllegalStateException("Palette count mismatch after resizing");
+        }
     }
 
     private int getPaletteIndex(int value) {
@@ -289,7 +297,9 @@ private int getPaletteIndex(int value) {
         final int lookup = valueToPaletteMap.putIfAbsent(value, lastPaletteIndex);
         if (lookup != -1) return lookup;
         this.paletteToValueList.add(value);
-        assert lastPaletteIndex < maxPaletteSize(bpe);
+        if (lastPaletteIndex >= maxPaletteSize(bpe)) {
+            throw new IllegalStateException("Palette size exceeded after adding new value");
+        }
         return lastPaletteIndex;
     }
 

src/main/java/net/minestom/server/network/NetworkBufferTypeImpl.java

@@ -269,7 +269,9 @@ public void write(@NotNull NetworkBuffer buffer, byte[] value) {
         public byte[] read(@NotNull NetworkBuffer buffer) {
             final int limit = buffer.nioBuffer.limit();
             final int length = limit - buffer.readIndex();
-            assert length >= 0 : "Invalid remaining: " + length;
+            if (length < 0) {
+                throw new IllegalStateException("Invalid remaining: " + length);
+            }
             final byte[] bytes = new byte[length];
             buffer.nioBuffer.get(buffer.readIndex(), bytes);
             buffer.readIndex += length;

src/main/java/net/minestom/server/network/PacketProcessor.java

@@ -37,7 +37,9 @@ public PacketProcessor(@NotNull PacketListenerManager packetListenerManager) {
         NetworkBuffer buffer = new NetworkBuffer(body);
         final ClientPacket clientPacket = switch (connectionState) {
             case HANDSHAKE -> {
-                assert packetId == 0;
+                if (packetId != 0) {
+                    throw new IllegalArgumentException("Invalid packetId for HANDSHAKE state. Expected packetId 0.");
+                }
                 yield new ClientHandshakePacket(buffer);
             }
             case STATUS -> statusHandler.create(packetId, buffer);
@@ -57,7 +59,9 @@ public ClientPacket process(@NotNull PlayerConnection connection, int packetId,
         }
 
         final Player player = connection.getPlayer();
-        assert player != null;
+        if (player == null) {
+            throw new IllegalStateException("Player should not be null");
+        }
         player.addPacketToQueue(packet);
         return packet;
     }

src/main/java/net/minestom/server/network/packet/client/play/ClientAdvancementTabPacket.java

@@ -34,7 +34,9 @@ private static ClientAdvancementTabPacket read(@NotNull NetworkBuffer reader) {
     public void write(@NotNull NetworkBuffer writer) {
         writer.writeEnum(AdvancementAction.class, action);
         if (action == AdvancementAction.OPENED_TAB) {
-            assert tabIdentifier != null;
+            if (tabIdentifier == null) {
+                throw new IllegalStateException("Tab identifier must not be null.");
+            }
             if (tabIdentifier.length() > 256) {
                 throw new IllegalArgumentException("Tab identifier cannot be longer than 256 characters.");
             }