feat(treecursor): allow custom allocators in getCurrentNode

Author: Emmeral

src/main/java/io/github/treesitter/jtreesitter/TreeCursor.java

@@ -4,6 +4,7 @@
 
 import java.lang.foreign.Arena;
 import java.lang.foreign.MemorySegment;
+import java.lang.foreign.SegmentAllocator;
 import java.util.OptionalInt;
 import org.jspecify.annotations.NullMarked;
 import org.jspecify.annotations.Nullable;
@@ -36,7 +37,11 @@ private TreeCursor(TreeCursor cursor) {
         node = cursor.node;
     }
 
-    /** Get the current node of the cursor. */
+    /**
+     * Get the current node of the cursor.
+     *
+     * @implNote The node will become invalid once the cursor is closed.
+     */
     public Node getCurrentNode() {
         if (this.node == null) {
             var node = ts_tree_cursor_current_node(arena, self);
@@ -45,6 +50,16 @@ public Node getCurrentNode() {
         return this.node;
     }
 
+    /**
+     * Get the current node of the cursor using the given allocator.
+     *
+     * @since 0.25.0
+     */
+    public Node getCurrentNode(SegmentAllocator allocator) {
+        var node = ts_tree_cursor_current_node(allocator, self);
+        return new Node(node, tree);
+    }
+
     /**
      * Get the depth of the cursor's current node relative to
      * the original node that the cursor was constructed with.

src/test/java/io/github/treesitter/jtreesitter/TreeCursorTest.java

@@ -3,7 +3,13 @@
 import static org.junit.jupiter.api.Assertions.*;
 
 import io.github.treesitter.jtreesitter.languages.TreeSitterJava;
-import org.junit.jupiter.api.*;
+import java.lang.foreign.Arena;
+import org.junit.jupiter.api.AfterAll;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
 
 class TreeCursorTest {
     private static Tree tree;
@@ -37,6 +43,15 @@ void getCurrentNode() {
         var node = cursor.getCurrentNode();
         assertEquals(tree.getRootNode(), node);
         assertSame(node, cursor.getCurrentNode());
+
+        try (var arena = Arena.ofConfined()) {
+            try (var copy = cursor.clone()) {
+                node = copy.getCurrentNode(arena);
+                assertEquals(node, tree.getRootNode());
+            }
+            // can still access node after cursor was closed
+            assertEquals(node, tree.getRootNode());
+        }
     }
 
     @Test