Make chunk sections only be considered all air if filled with Blocks.AIR only

patches/net/minecraft/world/level/chunk/LevelChunkSection.java.patch

@@ -0,0 +1,20 @@
+--- a/net/minecraft/world/level/chunk/LevelChunkSection.java
++++ b/net/minecraft/world/level/chunk/LevelChunkSection.java
+@@ -65,7 +_,7 @@
+
+         FluidState fluidstate = blockstate.getFluidState();
+         FluidState fluidstate1 = p_62995_.getFluidState();
+-        if (!blockstate.isAir()) {
++        if (!blockstate.isEmpty()) { // Neo: Fix MC-232360 for modded blocks (Makes modded isAir blocks not be replaced with Blocks.AIR in all-air chunk sections)
+             --this.nonEmptyBlockCount;
+             if (blockstate.isRandomlyTicking()) {
+                 --this.tickingBlockCount;
+@@ -76,7 +_,7 @@
+             --this.tickingFluidCount;
+         }
+
+-        if (!p_62995_.isAir()) {
++        if (!p_62995_.isEmpty()) { // Neo: Fix MC-232360 for modded blocks (Makes modded isAir blocks not be replaced with Blocks.AIR in all-air chunk sections)
+             ++this.nonEmptyBlockCount;
+             if (p_62995_.isRandomlyTicking()) {
+                 ++this.tickingBlockCount;

src/main/java/net/neoforged/neoforge/common/extensions/IBlockExtension.java

@@ -947,4 +947,14 @@ default BlockState getAppearance(BlockState state, BlockAndTintGetter level, Blo
     default PushReaction getPistonPushReaction(BlockState state) {
         return null;
     }
+
+    /**
+     * Return true if the state is able to be replaced with Blocks.AIR in chunk sections that is entirely made of blocks that return true for isEmpty
+     *
+     * @param state The current state
+     * @return True if the block should be allowed to be optimized away into Blocks.AIR
+     */
+    default boolean isEmpty(BlockState state) {
+        return state.is(Blocks.AIR) || state.is(Blocks.CAVE_AIR) || state.is(Blocks.VOID_AIR);
+    }
 }

src/main/java/net/neoforged/neoforge/common/extensions/IBlockStateExtension.java

@@ -721,4 +721,13 @@ default boolean canBeHydrated(BlockGetter getter, BlockPos pos, FluidState fluid
     default BlockState getAppearance(BlockAndTintGetter level, BlockPos pos, Direction side, @Nullable BlockState queryState, @Nullable BlockPos queryPos) {
         return self().getBlock().getAppearance(self(), level, pos, side, queryState, queryPos);
     }
+
+    /**
+     * Return true if the state is able to be replaced with Blocks.AIR in chunk sections that is entirely made of blocks that return true for isEmpty
+     *
+     * @return True if the block should be allowed to be optimized away into Blocks.AIR
+     */
+    default boolean isEmpty() {
+        return self().getBlock().isEmpty(self());
+    }
 }