Fix view tag access

Signed-off-by: TheMode <themode@outlook.fr>

src/main/java/net/minestom/server/tag/Tag.java

@@ -12,6 +12,7 @@ import org.jglrxavpok.hephaistos.nbt.NBTList;
 import org.jglrxavpok.hephaistos.nbt.NBTType;
 import org.jglrxavpok.hephaistos.nbt.mutable.MutableNBTCompound;
 
+import java.util.Arrays;
 import java.util.List;
 import java.util.function.Function;
 import java.util.function.Supplier;
@@ -163,7 +164,9 @@ public class Tag<T> {
         }
         PathEntry[] pathEntries = new PathEntry[path.length];
         for (int i = 0; i < path.length; i++) {
-            var name = path[i];
+            final String name = path[i];
+            if (name == null || name.isEmpty())
+                throw new IllegalArgumentException("Path must not be empty: " + Arrays.toString(path));
             pathEntries[i] = new PathEntry(name, INDEX_MAP.get(name));
         }
         return new Tag<>(index, key, readComparator, entry, defaultValue, pathEntries, copy, listScope);
@@ -244,6 +247,10 @@ public class Tag<T> {
         return tag(key, (Serializers.Entry<T, ? extends NBT>) Serializers.NBT_ENTRY);
     }
 
+    public static @NotNull Tag<ItemStack> ItemStack(@NotNull String key) {
+        return tag(key, Serializers.ITEM);
+    }
+
     /**
      * Create a wrapper around a compound.
      *
@@ -256,17 +263,19 @@ public class Tag<T> {
         return fromSerializer(key, serializer);
     }
 
-    @ApiStatus.Experimental
-    public static <T extends Record> @NotNull Tag<T> Structure(@NotNull String key, @NotNull Class<T> type) {
-        assert type.isRecord();
-        return fromSerializer(key, TagRecord.serializer(type));
-    }
-
     public static <T> @NotNull Tag<T> View(@NotNull TagSerializer<T> serializer) {
         return Structure("", serializer);
     }
 
-    public static @NotNull Tag<ItemStack> ItemStack(@NotNull String key) {
-        return tag(key, Serializers.ITEM);
+    @ApiStatus.Experimental
+    public static <T extends Record> @NotNull Tag<T> Structure(@NotNull String key, @NotNull Class<T> type) {
+        assert type.isRecord();
+        return Structure(key, TagRecord.serializer(type));
+    }
+
+    @ApiStatus.Experimental
+    public static <T extends Record> @NotNull Tag<T> View(@NotNull Class<T> type) {
+        assert type.isRecord();
+        return View(TagRecord.serializer(type));
     }
 }

src/main/java/net/minestom/server/tag/TagHandlerImpl.java

@@ -18,6 +18,7 @@ final class TagHandlerImpl implements TagHandler {
 
     @Override
     public <T> @UnknownNullability T getTag(@NotNull Tag<T> tag) {
+        if (tag.getKey().isEmpty()) return tag.read(asCompound());
         return read(entries, tag);
     }
 
@@ -28,7 +29,14 @@ final class TagHandlerImpl implements TagHandler {
             final UnaryOperator<T> copy = tag.copy;
             if (copy != null) value = copy.apply(value);
         }
-
+        // View tag access
+        if (tag.getKey().isEmpty()) {
+            MutableNBTCompound tmp = new MutableNBTCompound();
+            tag.writeUnsafe(tmp, value);
+            updateContent(tmp);
+            return;
+        }
+        // Normal write
         int tagIndex = tag.index;
         TagHandlerImpl local = this;
         Entry<?>[] entries = this.entries;
@@ -171,6 +179,7 @@ final class TagHandlerImpl implements TagHandler {
 
         @Override
         public <T> @UnknownNullability T getTag(@NotNull Tag<T> tag) {
+            if (tag.getKey().isEmpty()) return tag.read(compound);
             return read(entries, tag);
         }
     }

src/main/java/net/minestom/server/tag/TagRecord.java

@@ -58,7 +58,7 @@ final class TagRecord {
         }
     };
 
-    public static <T extends Record> @NotNull Serializer<T> serializer(@NotNull Class<T> type) {
+    static <T extends Record> @NotNull Serializer<T> serializer(@NotNull Class<T> type) {
         //noinspection unchecked
         return (Serializer<T>) serializers.get(type);
     }

src/test/java/net/minestom/server/tag/TagPathTest.java

@@ -27,6 +27,12 @@ public class TagPathTest {
         assertNull(handler.getTag(tag));
     }
 
+    @Test
+    public void invalidPath() {
+        assertThrows(IllegalArgumentException.class, () -> Tag.Integer("number").path(""));
+        assertThrows(IllegalArgumentException.class, () -> Tag.Integer("number").path("path", null));
+    }
+
     @Test
     public void emptyRemoval() {
         var handler = TagHandler.newHandler();

src/test/java/net/minestom/server/tag/TagRecordTest.java

@@ -25,6 +25,27 @@ public class TagRecordTest {
         assertEquals(vec, handler.getTag(tag));
     }
 
+    @Test
+    public void fromNBT() {
+        var vecCompound = NBT.Compound(Map.of(
+                "x", NBT.Double(1),
+                "y", NBT.Double(2),
+                "z", NBT.Double(3)));
+        var handler = TagHandler.fromCompound(NBT.Compound(Map.of("vec", vecCompound)));
+        var tag = Tag.Structure("vec", Vec.class);
+        assertEquals(new Vec(1, 2, 3), handler.getTag(tag));
+    }
+
+    @Test
+    public void fromNBTView() {
+        var handler = TagHandler.fromCompound(NBT.Compound(Map.of(
+                "x", NBT.Double(1),
+                "y", NBT.Double(2),
+                "z", NBT.Double(3))));
+        var tag = Tag.View(Vec.class);
+        assertEquals(new Vec(1, 2, 3), handler.getTag(tag));
+    }
+
     @Test
     public void basicSerializer() {
         var handler = TagHandler.newHandler();

src/test/java/net/minestom/server/tag/TagViewTest.java

@@ -58,4 +58,23 @@ public class TagViewTest {
         assertEqualsSNBT("{}", handler.asCompound());
     }
 
+    @Test
+    public void snbtOverride() {
+        var handler = TagHandler.newHandler();
+        var entry = new Entry("hello");
+        handler.setTag(VIEW_TAG, entry);
+        assertEqualsSNBT("""
+                {
+                  "value":"hello"
+                }
+                """, handler.asCompound());
+
+        handler.setTag(Tag.Integer("value"), 5);
+        assertEqualsSNBT("""
+                {
+                  "value":5,
+                }
+                """, handler.asCompound());
+    }
+
 }