Fix #4573 by using an existing utitlity that re-ids blocks when we duplicate a sprite.

src/sprites/sprite.js

@@ -2,6 +2,7 @@ const RenderedTarget = require('./rendered-target');
 const Blocks = require('../engine/blocks');
 const {loadSoundFromAsset} = require('../import/load-sound');
 const {loadCostumeFromAsset} = require('../import/load-costume');
+const newBlockIds = require('../util/new-block-ids');
 const StringUtil = require('../util/string-util');
 const StageLayering = require('../engine/stage-layering');
 
@@ -136,8 +137,12 @@ class Sprite {
 
     duplicate () {
         const newSprite = new Sprite(null, this.runtime);
+        const copiedBlocks = JSON.parse(JSON.stringify(Object.values(this.blocks._blocks)));
+        newBlockIds(copiedBlocks);
+        copiedBlocks.forEach(block => {
+            newSprite.blocks.createBlock(block);
+        });
 
-        newSprite.blocks = this.blocks.duplicate();
 
         const allNames = this.runtime.targets.map(t => t.sprite.name);
         newSprite.name = StringUtil.unusedName(this.name, allNames);

test/unit/sprites_rendered-target.js

@@ -1,4 +1,5 @@
 const test = require('tap').test;
+const Blocks = require('../../src/engine/blocks');
 const RenderedTarget = require('../../src/sprites/rendered-target');
 const Sprite = require('../../src/sprites/sprite');
 const Runtime = require('../../src/engine/runtime');
@@ -27,6 +28,24 @@ test('setxy', t => {
     t.end();
 });
 
+test('blocks get new id on duplicate', t => {
+    const r = new Runtime();
+    const s = new Sprite(null, r);
+    const rt = new RenderedTarget(s, r);
+    const block = {
+        id: 'id1',
+        topLevel: true,
+        fields: {}
+    };
+
+    rt.blocks.createBlock(block);
+
+    return rt.duplicate().then(duplicate => {
+        t.notOk(duplicate.blocks._blocks.hasOwnProperty(block.id));
+        t.end();
+    });
+});
+
 test('direction', t => {
     const r = new Runtime();
     const s = new Sprite(null, r);