fix(compiler-sfc): handle more edge cases in default rewrite

packages/compiler-sfc/__tests__/rewriteDefault.spec.ts

@@ -26,4 +26,55 @@ describe('compiler sfc: rewriteDefault', () => {
       const script = a"
     `)
   })
+
+  test('w/ comments', async () => {
+    expect(rewriteDefault(`// export default\nexport default {}`, 'script'))
+      .toMatchInlineSnapshot(`
+      "// export default
+      const script = {}"
+    `)
+  })
+
+  test('export default class', async () => {
+    expect(rewriteDefault(`export default class Foo {}`, 'script'))
+      .toMatchInlineSnapshot(`
+      "class Foo {}
+      const script = Foo"
+    `)
+  })
+
+  test('export default class w/ comments', async () => {
+    expect(
+      rewriteDefault(`// export default\nexport default class Foo {}`, 'script')
+    ).toMatchInlineSnapshot(`
+      "// export default
+      class Foo {}
+      const script = Foo"
+    `)
+  })
+
+  test('export default class w/ comments 2', async () => {
+    expect(
+      rewriteDefault(
+        `export default {}\n` + `// export default class Foo {}`,
+        'script'
+      )
+    ).toMatchInlineSnapshot(`
+      "const script = {}
+      // export default class Foo {}"
+    `)
+  })
+
+  test('export default class w/ comments 3', async () => {
+    expect(
+      rewriteDefault(
+        `/*\nexport default class Foo {}*/\n` + `export default class Bar {}`,
+        'script'
+      )
+    ).toMatchInlineSnapshot(`
+      "/*
+      export default class Foo {}*/
+      const script = class Bar {}"
+    `)
+  })
 })

packages/compiler-sfc/src/rewriteDefault.ts

@@ -3,6 +3,7 @@ import MagicString from 'magic-string'
 
 const defaultExportRE = /((?:^|\n|;)\s*)export(\s*)default/
 const namedDefaultExportRE = /((?:^|\n|;)\s*)export(.+)as(\s*)default/
+const exportDefaultClassRE = /((?:^|\n|;)\s*)export\s+default\s+class\s+([\w$]+)/
 
 /**
  * Utility for rewriting `export default` in a script block into a variable
@@ -17,7 +18,16 @@ export function rewriteDefault(
     return input + `\nconst ${as} = {}`
   }
 
-  const replaced = input.replace(defaultExportRE, `$1const ${as} =`)
+  let replaced: string | undefined
+
+  const classMatch = input.match(exportDefaultClassRE)
+  if (classMatch) {
+    replaced =
+      input.replace(exportDefaultClassRE, '$1class $2') +
+      `\nconst ${as} = ${classMatch[2]}`
+  } else {
+    replaced = input.replace(defaultExportRE, `$1const ${as} =`)
+  }
   if (!hasDefaultExport(replaced)) {
     return replaced
   }