Fix Scratch import/export reliability in IDE

src/components/scratch/ScratchPanel.tsx

@@ -3196,39 +3196,50 @@ export const ScratchPanel = ({ archive, onArchiveChange, onProjectJsonUpdate, is
       await loadVmFromArchive(normalizedArchive, inferredVersion);
     } catch (error) {
       setVmError(error instanceof Error ? error.message : 'Failed to import Scratch archive (.sb/.sb2/.sb3).');
+    } finally {
+      if (importInputRef.current) {
+        importInputRef.current.value = '';
+      }
     }
   };
 
   const handleExport = async () => {
-    const exportFormat = scratchVersion === 'scratch3' ? 'sb3' : 'sb2';
-    const semver = exportFormat === 'sb3' ? '3.0.0' : '2.0.0';
-    const currentProject = safeParseProject(archive);
-    const normalizedProject: ScratchProject = {
-      ...currentProject,
-      projectVersion: exportFormat === 'sb3' ? 3 : 2,
-      targets: (currentProject.targets || []).map((target) => ({
-        ...target,
-        blocks: normalizeBlocksForVersion(target.blocks, exportFormat === 'sb3' ? 'scratch3' : 'scratch2'),
-      })),
-      extensions: (currentProject.extensions || []).filter((ext) => exportFormat === 'sb3' || (ext !== 'pen' && ext !== 'music')),
-      meta: {
-        ...(currentProject.meta || {}),
-        semver,
-      },
-    };
-    const exportArchive = ensureArchive({
-      ...ensureArchive(archive),
-      projectJson: formatJson(normalizedProject),
-    });
-    const data = await exportScratchArchive(exportArchive, exportFormat);
-    const mime = exportFormat === 'sb3' ? 'application/x.scratch.sb3' : 'application/x.scratch.sb2';
-    const blob = new Blob([data.buffer.slice(data.byteOffset, data.byteOffset + data.byteLength) as ArrayBuffer], { type: mime });
-    const url = URL.createObjectURL(blob);
-    const a = document.createElement('a');
-    a.href = url;
-    a.download = `project.${exportFormat}`;
-    a.click();
-    URL.revokeObjectURL(url);
+    try {
+      const exportFormat = scratchVersion === 'scratch3' ? 'sb3' : 'sb2';
+      const semver = exportFormat === 'sb3' ? '3.0.0' : '2.0.0';
+      const currentProject = safeParseProject(archive);
+      const normalizedProject: ScratchProject = {
+        ...currentProject,
+        projectVersion: exportFormat === 'sb3' ? 3 : 2,
+        targets: (currentProject.targets || []).map((target) => ({
+          ...target,
+          blocks: normalizeBlocksForVersion(target.blocks, exportFormat === 'sb3' ? 'scratch3' : 'scratch2'),
+        })),
+        extensions: (currentProject.extensions || []).filter((ext) => exportFormat === 'sb3' || (ext !== 'pen' && ext !== 'music')),
+        meta: {
+          ...(currentProject.meta || {}),
+          semver,
+        },
+      };
+      const exportArchive = ensureArchive({
+        ...ensureArchive(archive),
+        projectJson: formatJson(normalizedProject),
+      });
+      const data = await exportScratchArchive(exportArchive, exportFormat);
+      const mime = exportFormat === 'sb3' ? 'application/x.scratch.sb3' : 'application/x.scratch.sb2';
+      const blob = new Blob([data.buffer.slice(data.byteOffset, data.byteOffset + data.byteLength) as ArrayBuffer], { type: mime });
+      const url = URL.createObjectURL(blob);
+      const a = document.createElement('a');
+      a.href = url;
+      a.download = `project.${exportFormat}`;
+      document.body.appendChild(a);
+      a.click();
+      a.remove();
+      window.setTimeout(() => URL.revokeObjectURL(url), 1000);
+      setVmError(null);
+    } catch (error) {
+      setVmError(error instanceof Error ? error.message : 'Failed to export Scratch archive (.sb2/.sb3).');
+    }
   };
 
   const applyJsonDraft = async () => {

src/services/scratchSb3.ts

@@ -76,7 +76,10 @@ const convertLegacyProjectToSb3 = async (arrayBuffer: ArrayBuffer): Promise<Arra
 
 export const exportSb3 = async (archive: ScratchArchive): Promise<Uint8Array> => {
   const zip = new JSZip();
-  const fileNames = archive.fileNames.length > 0 ? archive.fileNames : Object.keys(archive.files);
+  const fileNames = Array.from(new Set([
+    ...archive.fileNames,
+    ...Object.keys(archive.files),
+  ]));
 
   for (const name of fileNames) {
     if (name === 'project.json') continue;

src/test/scratchSb3.test.ts

@@ -23,4 +23,19 @@ describe('scratch sb3 import/export', () => {
     expect(outImported.archive.projectJson).toContain('Sprite1');
     expect(outImported.archive.files['a.txt']).toBeTruthy();
   });
+
+  it('exports assets present in files even when fileNames is stale', async () => {
+    const data = await exportSb3({
+      projectJson: JSON.stringify({ targets: [], meta: { semver: '3.0.0' } }),
+      files: {
+        'extra.txt': btoa('hello'),
+      },
+      fileNames: ['project.json'],
+    });
+
+    const out = data.buffer.slice(data.byteOffset, data.byteOffset + data.byteLength) as ArrayBuffer;
+    const imported = await importSb3(out);
+
+    expect(imported.archive.files['extra.txt']).toBeTruthy();
+  });
 });