fix: support xml serialized blocks in setContents() of workspace-back… (

#1835)

* fix: support xml serialized blocks in setContents() of workspace-backpack

* fix: remove extraneous ! for block Xml string type workspace-backpack's blockXmlToJsonString()

* fix: dispose workspace at the end of blockXmlToJsonString() in workspace-backpack

plugins/workspace-backpack/src/backpack.js

@@ -497,6 +497,29 @@ export class Backpack extends Blockly.DragTarget {
     return JSON.stringify(json);
   }
 
+  /**
+   * Converts serialized XML to its equivalent serialized JSON string
+   * @param {string} blockXml The XML serialized block.
+   * @returns {string} The JSON object as a string.
+   * @private
+   */
+  blockXmlToJsonString(blockXml) {
+    if (!blockXml.startsWith('<block')) {
+      throw new Error('Unrecognized XML format');
+    }
+
+    const workspace = new Blockly.Workspace();
+    try {
+      const block = Blockly.Xml.domToBlock(
+          Blockly.utils.xml.textToDom(blockXml),
+          workspace,
+      );
+      return this.blockToJsonString(block);
+    } finally {
+      workspace.dispose();
+    }
+  }
+
   /**
    * Returns whether the backpack contains a duplicate of the provided Block.
    * @param {!Blockly.Block} block The block to check.
@@ -574,7 +597,12 @@ export class Backpack extends Blockly.DragTarget {
    */
   setContents(contents) {
     this.contents_ = [];
-    this.contents_ = this.filterDuplicates_(contents);
+    this.contents_ = this.filterDuplicates_(
+        // Support XML serialized content for backwards compatiblity: https://github.com/google/blockly-samples/issues/1827
+        contents.map((content) => content.startsWith('<block') ?
+          this.blockXmlToJsonString(content) :
+          content)
+    );
     this.onContentChange_();
   }