chore: add test block that duplicates on drag (#2377)

Author: BeksOmega

plugins/block-test/src/drag.js

@@ -10,6 +10,47 @@
  * @author samelh@google.com (Sam El-Husseini)
  */
 
+import * as Blockly from 'blockly/core';
+
+/** Block that duplicates itself on drag. */
+Blockly.Blocks['drag_to_dupe'] = {
+  init: function () {
+    this.setOutput(true, null);
+    this.appendDummyInput().appendField('drag to dupe');
+    this.setDragStrategy(new DragToDupe(this));
+  },
+};
+
+/** Drag strategy that duplicates the block on drag. */
+class DragToDupe {
+  constructor(block) {
+    this.block = block;
+  }
+
+  isMovable() {
+    return true;
+  }
+
+  startDrag(e) {
+    const data = this.block.toCopyData();
+    this.copy = Blockly.clipboard.paste(data, this.block.workspace);
+    this.baseStrat = new Blockly.dragging.BlockDragStrategy(this.copy);
+    this.baseStrat.startDrag(e);
+  }
+
+  drag(e) {
+    this.baseStrat.drag(e);
+  }
+
+  endDrag(e) {
+    this.baseStrat.endDrag(e);
+  }
+
+  revertDrag(e) {
+    this.copy.dispose();
+  }
+}
+
 /**
  * The Drag category.
  */
@@ -127,6 +168,21 @@ export const category = {
   </statement>
 </block>`,
     },
+    {
+      kind: 'BLOCK',
+      type: 'drag_to_dupe',
+    },
+    {
+      kind: 'BLOCK',
+      type: 'text_print',
+      inputs: {
+        TEXT: {
+          shadow: {
+            type: 'drag_to_dupe',
+          },
+        },
+      },
+    },
   ],
 };