Include extension list in exported .sprite3 files

closes TurboWarp/extensions#767

src/serialization/sb3.js

@@ -610,24 +610,16 @@ const serialize = function (runtime, targetId, {allowOptimization = true} = {})
 
     const serializedTargets = flattenedOriginalTargets.map(t => serializeTarget(t, extensions));
 
-    if (targetId) {
-        return serializedTargets[0];
-    }
-
-    obj.targets = serializedTargets;
-
-    obj.monitors = serializeMonitors(runtime.getMonitorState(), runtime, extensions);
-
-    // Assemble extension list
-    obj.extensions = Array.from(extensions);
+    const serialiedExtensionList = Array.from(extensions);
 
     // Save list of URLs to load the current extensions
     // Extension manager only exists when runtime is wrapped by VirtualMachine
+    let serializedExtensionURLs = null;
     if (runtime.extensionManager) {
         // We'll save the extensions in the format:
         // {
-        //   "extension_id": "https://...",
-        //   "other_id": "https://..."
+        //   "extensionid": "https://...",
+        //   "otherid": "https://..."
         // }
         // Which lets the VM know which URLs correspond to which IDs, which is useful when the project
         // is being loaded. For example, if the extension is eventually converted to a builtin extension
@@ -642,10 +634,36 @@ const serialize = function (runtime, targetId, {allowOptimization = true} = {})
         }
         // Only save this object if any URLs would actually be saved.
         if (Object.keys(urlsToSave).length !== 0) {
-            obj.extensionURLs = urlsToSave;
+            serializedExtensionURLs = urlsToSave;
         }
     }
 
+    if (targetId) {
+        const target = serializedTargets[0];
+
+        // Scratch doesn't save extensions for sprites, so don't add if not needed.
+        if (serialiedExtensionList.length) {
+            target.extensions = serialiedExtensionList;
+        }
+        if (serializedExtensionURLs) {
+            target.extensionURLs = serializedExtensionURLs;
+        }
+
+        return serializedTargets[0];
+    }
+
+    // This is part of Scratch
+    obj.extensions = serialiedExtensionList;
+
+    // This is not part of Scratch, so don't add if not needed.
+    if (serializedExtensionURLs) {
+        obj.extensionURLs = serializedExtensionURLs;
+    }
+
+    obj.targets = serializedTargets;
+
+    obj.monitors = serializeMonitors(runtime.getMonitorState(), runtime, extensions);
+
     // Assemble metadata
     const meta = Object.create(null);
     meta.semver = '3.0.0';

test/integration/tw_serialize_extensions.js

@@ -4,6 +4,8 @@ const RenderedTarget = require('../../src/sprites/rendered-target');
 const Sprite = require('../../src/sprites/sprite');
 
 test('Serializes custom extensions', t => {
+    t.plan(6);
+
     const vm = new VirtualMachine();
 
     // Trick the extension manager into thinking a couple extensions are loaded.
@@ -13,21 +15,34 @@ test('Serializes custom extensions', t => {
     vm.extensionManager._loadedExtensions.set('test1', 'test.0.0');
     vm.extensionManager._loadedExtensions.set('test2', 'test.1.0');
 
-    // Create a block that uses the first extension
-    const sprite = new Sprite(null, vm.runtime);
-    const target = new RenderedTarget(sprite, vm.runtime);
-    target.blocks.createBlock({
+    const targetUsingBlock = new RenderedTarget(new Sprite(null, vm.runtime), vm.runtime);
+    vm.runtime.addTarget(targetUsingBlock);
+    targetUsingBlock.blocks.createBlock({
         id: 'a',
         opcode: 'test1_something'
     });
-    vm.runtime.addTarget(target);
+
+    const targetNotUsingBlock = new RenderedTarget(new Sprite(null, vm.runtime), vm.runtime);
+    vm.runtime.addTarget(targetNotUsingBlock);
 
     // test2 isn't used, so it shouldn't be included in the JSON
-    const serialized = JSON.parse(vm.toJSON());
-    t.same(serialized.extensions, ['test1']);
-    t.same(serialized.extensionURLs, {
+
+    const serializedProject = JSON.parse(vm.toJSON());
+    t.same(serializedProject.extensions, ['test1'], 'save extension IDs for project');
+    t.same(serializedProject.extensionURLs, {
         test1: 'https://example.com/test1.js'
-    });
+    }, 'save extension URLs for project');
+
+    const serializedTargetWithBlock = JSON.parse(vm.toJSON(targetUsingBlock.id));
+    t.same(serializedTargetWithBlock.extensions, ['test1'], 'save extension IDs for sprite');
+    t.same(serializedTargetWithBlock.extensionURLs, {
+        test1: 'https://example.com/test1.js'
+    }, 'save extension URLs for sprite');
+
+    // other sprite uses no extensions, so don't want extension stuff in the JSON
+    const serializedTargetWithoutBlock = JSON.parse(vm.toJSON(targetNotUsingBlock.id));
+    t.notOk('extensions' in serializedTargetWithoutBlock, 'dont save extension IDs for empty sprite');
+    t.notOk('extensionURLs' in serializedTargetWithoutBlock, 'dont save extension URLs for empty sprite');
 
     t.end();
 });