Merge pull request #1833 from kchadha/fix-sb2-from-sb1-import

Fix issue importing some sb2s that were originally sb1s, with baseLayerMd5 property formatted differently.

src/serialization/sb2.js

@@ -442,7 +442,15 @@ const parseScratchObject = function (object, runtime, extensions, topLevel, zip)
             const md5ext = costumeSource.baseLayerMD5;
             const idParts = StringUtil.splitFirst(md5ext, '.');
             const md5 = idParts[0];
-            const ext = idParts[1].toLowerCase();
+            let ext;
+            if (idParts.length === 2 && idParts[1]) {
+                ext = idParts[1];
+            } else {
+                // Default to 'png' if baseLayerMD5 is not formatted correctly
+                ext = 'png';
+                // Fix costume md5 for later
+                costume.md5 = `${costume.md5}.${ext}`;
+            }
             costume.dataFormat = ext;
             costume.assetId = md5;
             if (costumeSource.textLayerMD5) {

test/integration/load-sb2-originally-sb1-without-backdrop-image.js

@@ -0,0 +1,41 @@
+const path = require('path');
+const test = require('tap').test;
+const makeTestStorage = require('../fixtures/make-test-storage');
+const readFileToBuffer = require('../fixtures/readProjectFile').readFileToBuffer;
+
+const VirtualMachine = require('../../src/virtual-machine');
+
+const projectUri = path.resolve(__dirname, '../fixtures/sb2-from-sb1-missing-backdrop-image.sb2');
+const project = readFileToBuffer(projectUri);
+
+const vm = new VirtualMachine();
+
+test('sb2 project (originally from Scratch 1.4) with missing backdrop image should load', t => {
+    vm.attachStorage(makeTestStorage());
+
+    // Evaluate playground data and exit
+    vm.on('playgroundData', e => {
+        const threads = JSON.parse(e.threads);
+        t.ok(threads.length === 0);
+        t.end();
+        process.nextTick(process.exit);
+    });
+
+    vm.start();
+    vm.clear();
+    vm.setCompatibilityMode(false);
+    vm.setTurboMode(false);
+    t.doesNotThrow(() => {
+        vm.loadProject(project).then(() => {
+
+            t.equal(vm.runtime.targets.length, 2); // stage and default sprite
+
+            vm.greenFlag();
+
+            setTimeout(() => {
+                vm.getPlaygroundData();
+                vm.stopAll();
+            }, 1000);
+        });
+    });
+});