noclip can place blocks intersecting with sefl

src/main/java/carpet/mixins/BlockItem_creativeNoClipMixin.java

@@ -0,0 +1,36 @@
+package carpet.mixins;
+
+import carpet.CarpetSettings;
+import net.minecraft.block.BlockState;
+import net.minecraft.entity.EntityContext;
+import net.minecraft.entity.player.PlayerEntity;
+import net.minecraft.item.BlockItem;
+import net.minecraft.item.ItemPlacementContext;
+import net.minecraft.util.math.BlockPos;
+import net.minecraft.util.shape.VoxelShape;
+import net.minecraft.world.World;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Redirect;
+
+@Mixin(BlockItem.class)
+public class BlockItem_creativeNoClipMixin
+{
+    @Redirect(method = "canPlace", at = @At(
+            value = "INVOKE",
+            target = "Lnet/minecraft/world/World;canPlace(Lnet/minecraft/block/BlockState;Lnet/minecraft/util/math/BlockPos;Lnet/minecraft/entity/EntityContext;)Z"
+    ))
+    private boolean canSpectatingPlace(World world, BlockState state, BlockPos pos, EntityContext context,
+                                       ItemPlacementContext contextOuter, BlockState stateOuter)
+    {
+        PlayerEntity player = contextOuter.getPlayer();
+        if (CarpetSettings.creativeNoClip && player != null && player.isCreative() && player.abilities.flying)
+        {
+            // copy from canPlace
+            VoxelShape voxelShape = state.getCollisionShape(world, pos, context);
+            return voxelShape.isEmpty() || world.intersectsEntities(player, voxelShape.offset(pos.getX(), pos.getY(), pos.getZ()));
+
+        }
+        return world.canPlace(state, pos, context);
+    }
+}

src/main/resources/carpet.mixins.json

@@ -158,7 +158,8 @@
     "WorldChunk_movableTEMixin",
     "PistonHandler_movableTEMixin",
     "PlayerEntity_creativeNoClipMixin",
-    "PistonBlockEntity_creativeNoClipMixin"
+    "PistonBlockEntity_creativeNoClipMixin",
+    "BlockItem_creativeNoClipMixin"
 
   ],
   "client": [