fix(ssr): fix live binding of default export declaration and hoist exports getter (#19842)

hi-ogawa · web-flow · commit 80a91ff82426 · 2025-04-21T15:59:46.000+09:00
diff --git a/packages/vite/src/node/ssr/__tests__/ssrLoadModule.spec.ts b/packages/vite/src/node/ssr/__tests__/ssrLoadModule.spec.ts
@@ -235,7 +235,7 @@ test('json', async () => {
     null,
     '/test.json',
   )
-  expect(json?.code.length).toMatchInlineSnapshot(`61`)
+  expect(json?.code.length).toMatchInlineSnapshot(`208`)
 })
 
 test('file url', async () => {
diff --git a/packages/vite/src/node/ssr/__tests__/ssrTransform.spec.ts b/packages/vite/src/node/ssr/__tests__/ssrTransform.spec.ts
@@ -221,9 +221,11 @@ test('export as from arbitrary module namespace identifier', async () => {
 })
 
 test('export default', async () => {
-  expect(
-    await ssrTransformSimpleCode(`export default {}`),
-  ).toMatchInlineSnapshot(`"__vite_ssr_exports__.default = {}"`)
+  expect(await ssrTransformSimpleCode(`export default {}`))
+    .toMatchInlineSnapshot(`
+    "Object.defineProperty(__vite_ssr_exports__, "default", { enumerable: true, configurable: true, get(){ return __vite_ssr_export_default__ }});
+    const __vite_ssr_export_default__ = {}"
+  `)
 })
 
 test('export then import minified', async () => {
@@ -505,11 +507,11 @@ test('should declare variable for imported super class', async () => {
         `export class B extends Foo {}`,
     ),
   ).toMatchInlineSnapshot(`
-    "Object.defineProperty(__vite_ssr_exports__, "B", { enumerable: true, configurable: true, get(){ return B }});
+    "Object.defineProperty(__vite_ssr_exports__, "default", { enumerable: true, configurable: true, get(){ return A }});
+    Object.defineProperty(__vite_ssr_exports__, "B", { enumerable: true, configurable: true, get(){ return B }});
     const __vite_ssr_import_0__ = await __vite_ssr_import__("./dependency", {"importedNames":["Foo"]});const Foo = __vite_ssr_import_0__.Foo;
     class A extends Foo {};
-    class B extends Foo {}
-    Object.defineProperty(__vite_ssr_exports__, "default", { enumerable: true, configurable: true, value: A });"
+    class B extends Foo {}"
   `)
 })
 
@@ -518,13 +520,15 @@ test('should handle default export variants', async () => {
   // default anonymous functions
   expect(await ssrTransformSimpleCode(`export default function() {}\n`))
     .toMatchInlineSnapshot(`
-      "__vite_ssr_exports__.default = function() {}
+      "Object.defineProperty(__vite_ssr_exports__, "default", { enumerable: true, configurable: true, get(){ return __vite_ssr_export_default__ }});
+      const __vite_ssr_export_default__ = function() {}
       "
     `)
   // default anonymous class
   expect(await ssrTransformSimpleCode(`export default class {}\n`))
     .toMatchInlineSnapshot(`
-      "__vite_ssr_exports__.default = class {}
+      "Object.defineProperty(__vite_ssr_exports__, "default", { enumerable: true, configurable: true, get(){ return __vite_ssr_export_default__ }});
+      const __vite_ssr_export_default__ = class {}
       "
     `)
   // default named functions
@@ -534,20 +538,20 @@ test('should handle default export variants', async () => {
         `foo.prototype = Object.prototype;`,
     ),
   ).toMatchInlineSnapshot(`
-    "function foo() {};
-    foo.prototype = Object.prototype;
-    Object.defineProperty(__vite_ssr_exports__, "default", { enumerable: true, configurable: true, value: foo });"
+    "Object.defineProperty(__vite_ssr_exports__, "default", { enumerable: true, configurable: true, get(){ return foo }});
+    function foo() {};
+    foo.prototype = Object.prototype;"
   `)
   // default named classes
   expect(
     await ssrTransformSimpleCode(
       `export default class A {}\n` + `export class B extends A {}`,
     ),
   ).toMatchInlineSnapshot(`
-    "Object.defineProperty(__vite_ssr_exports__, "B", { enumerable: true, configurable: true, get(){ return B }});
+    "Object.defineProperty(__vite_ssr_exports__, "default", { enumerable: true, configurable: true, get(){ return A }});
+    Object.defineProperty(__vite_ssr_exports__, "B", { enumerable: true, configurable: true, get(){ return B }});
     class A {};
-    class B extends A {}
-    Object.defineProperty(__vite_ssr_exports__, "default", { enumerable: true, configurable: true, value: A });"
+    class B extends A {}"
   `)
 })
 
@@ -1007,14 +1011,17 @@ export default (function getRandom() {
 `.trim()
 
   expect(await ssrTransformSimpleCode(code)).toMatchInlineSnapshot(`
-    "__vite_ssr_exports__.default = (function getRandom() {
+    "Object.defineProperty(__vite_ssr_exports__, "default", { enumerable: true, configurable: true, get(){ return __vite_ssr_export_default__ }});
+    const __vite_ssr_export_default__ = (function getRandom() {
       return Math.random();
     });"
   `)
 
-  expect(
-    await ssrTransformSimpleCode(`export default (class A {});`),
-  ).toMatchInlineSnapshot(`"__vite_ssr_exports__.default = (class A {});"`)
+  expect(await ssrTransformSimpleCode(`export default (class A {});`))
+    .toMatchInlineSnapshot(`
+    "Object.defineProperty(__vite_ssr_exports__, "default", { enumerable: true, configurable: true, get(){ return __vite_ssr_export_default__ }});
+    const __vite_ssr_export_default__ = (class A {});"
+  `)
 })
 
 // #8002
@@ -1278,10 +1285,11 @@ export * as bar from './bar'
 console.log(bar)
   `),
   ).toMatchInlineSnapshot(`
-    "Object.defineProperty(__vite_ssr_exports__, "bar", { enumerable: true, configurable: true, get(){ return __vite_ssr_import_1__ }});
+    "Object.defineProperty(__vite_ssr_exports__, "default", { enumerable: true, configurable: true, get(){ return __vite_ssr_export_default__ }});
+    Object.defineProperty(__vite_ssr_exports__, "bar", { enumerable: true, configurable: true, get(){ return __vite_ssr_import_1__ }});
 
     const __vite_ssr_import_0__ = await __vite_ssr_import__("./foo", {"importedNames":["foo"]});
-    __vite_ssr_exports__.default = (0,__vite_ssr_import_0__.foo)();
+    const __vite_ssr_export_default__ = (0,__vite_ssr_import_0__.foo)();
     const __vite_ssr_import_1__ = await __vite_ssr_import__("./bar");;
     console.log(bar)
       "
@@ -1503,7 +1511,7 @@ test('combine mappings', async () => {
     expect(result?.map).toMatchInlineSnapshot(`
       SourceMap {
         "file": undefined,
-        "mappings": "AAAA,8BAAc,CAAC,CAAC,IAAI,CAAC;",
+        "mappings": ";AAAA,mCAAc,CAAC,CAAC,IAAI,CAAC;",
         "names": [],
         "sources": [
           "virtual:test-mappings:null",
diff --git a/packages/vite/src/node/ssr/runtime/__tests__/fixtures/cyclic2/test9/dep.js b/packages/vite/src/node/ssr/runtime/__tests__/fixtures/cyclic2/test9/dep.js
@@ -0,0 +1,2 @@
+import dep from "./index.js"
+export default dep
diff --git a/packages/vite/src/node/ssr/runtime/__tests__/fixtures/cyclic2/test9/index.js b/packages/vite/src/node/ssr/runtime/__tests__/fixtures/cyclic2/test9/index.js
@@ -0,0 +1,2 @@
+import dep from "./dep.js";
+export default dep
diff --git a/packages/vite/src/node/ssr/runtime/__tests__/fixtures/live-binding/package.json b/packages/vite/src/node/ssr/runtime/__tests__/fixtures/live-binding/package.json
@@ -0,0 +1,3 @@
+{
+  "type": "module"
+}
diff --git a/packages/vite/src/node/ssr/runtime/__tests__/fixtures/live-binding/test1/dep.js b/packages/vite/src/node/ssr/runtime/__tests__/fixtures/live-binding/test1/dep.js
@@ -0,0 +1,11 @@
+export default function f() {
+  return 0;
+}
+
+f = () => 1;
+
+f = () => 2;
+
+export function update() {
+  f = () => 3;
+}
diff --git a/packages/vite/src/node/ssr/runtime/__tests__/fixtures/live-binding/test1/index.js b/packages/vite/src/node/ssr/runtime/__tests__/fixtures/live-binding/test1/index.js
@@ -0,0 +1,6 @@
+import f, { update } from "./dep.js";
+
+const x = f();
+update();
+const y = f();
+export default [x, y];
diff --git a/packages/vite/src/node/ssr/runtime/__tests__/fixtures/live-binding/test2/dep.js b/packages/vite/src/node/ssr/runtime/__tests__/fixtures/live-binding/test2/dep.js
@@ -0,0 +1,13 @@
+function f() {
+  return 0;
+}
+
+f = () => 1;
+
+export default f;
+
+f = () => 2;
+
+export function update() {
+  f = () => 3;
+}
diff --git a/packages/vite/src/node/ssr/runtime/__tests__/fixtures/live-binding/test2/index.js b/packages/vite/src/node/ssr/runtime/__tests__/fixtures/live-binding/test2/index.js
@@ -0,0 +1,6 @@
+import f, { update } from "./dep.js";
+
+const x = f();
+update();
+const y = f();
+export default [x, y];
diff --git a/packages/vite/src/node/ssr/runtime/__tests__/fixtures/live-binding/test3/dep.js b/packages/vite/src/node/ssr/runtime/__tests__/fixtures/live-binding/test3/dep.js
@@ -0,0 +1,13 @@
+function f() {
+  return 0;
+}
+
+f = () => 1
+
+export { f as default }
+
+f = () => 2
+
+export function update() {
+  f = () => 3;
+}
diff --git a/packages/vite/src/node/ssr/runtime/__tests__/fixtures/live-binding/test3/index.js b/packages/vite/src/node/ssr/runtime/__tests__/fixtures/live-binding/test3/index.js
@@ -0,0 +1,6 @@
+import f, { update } from "./dep.js";
+
+const x = f();
+update();
+const y = f();
+export default [x, y];
diff --git a/packages/vite/src/node/ssr/runtime/__tests__/fixtures/live-binding/test4/dep.js b/packages/vite/src/node/ssr/runtime/__tests__/fixtures/live-binding/test4/dep.js
@@ -0,0 +1,17 @@
+export default class C {
+  static f = () => 0;
+}
+
+C = class {
+  static f = () => 1;
+}
+
+C = class {
+  static f = () => 2;
+}
+
+export function update() {
+  C = class {
+    static f = () => 3;
+  }
+}
diff --git a/packages/vite/src/node/ssr/runtime/__tests__/fixtures/live-binding/test4/index.js b/packages/vite/src/node/ssr/runtime/__tests__/fixtures/live-binding/test4/index.js
@@ -0,0 +1,6 @@
+import C, { update } from "./dep.js";
+
+const x = C.f();
+update();
+const y = C.f();
+export default [x, y];
diff --git a/packages/vite/src/node/ssr/runtime/__tests__/server-runtime.spec.ts b/packages/vite/src/node/ssr/runtime/__tests__/server-runtime.spec.ts
@@ -301,6 +301,55 @@ describe('module runner initialization', async () => {
       `[ReferenceError: Cannot access 'dep1' before initialization]`,
     )
   })
+
+  it(`live binding (export default function f)`, async ({ runner }) => {
+    const mod = await runner.import('/fixtures/live-binding/test1/index.js')
+    expect(mod.default).toMatchInlineSnapshot(`
+      [
+        2,
+        3,
+      ]
+    `)
+  })
+
+  it(`live binding (export default f)`, async ({ runner }) => {
+    const mod = await runner.import('/fixtures/live-binding/test2/index.js')
+    expect(mod.default).toMatchInlineSnapshot(`
+      [
+        1,
+        1,
+      ]
+    `)
+  })
+
+  it(`live binding (export { f as default })`, async ({ runner }) => {
+    const mod = await runner.import('/fixtures/live-binding/test3/index.js')
+    expect(mod.default).toMatchInlineSnapshot(`
+      [
+        2,
+        3,
+      ]
+    `)
+  })
+
+  it(`live binding (export default class C)`, async ({ runner }) => {
+    const mod = await runner.import('/fixtures/live-binding/test4/index.js')
+    expect(mod.default).toMatchInlineSnapshot(`
+      [
+        2,
+        3,
+      ]
+    `)
+  })
+
+  it(`export default getter is hoisted`, async ({ runner }) => {
+    // Node error is `ReferenceError: Cannot access 'dep' before initialization`
+    await expect(() =>
+      runner.import('/fixtures/cyclic2/test9/index.js'),
+    ).rejects.toMatchInlineSnapshot(
+      `[ReferenceError: Cannot access '__vite_ssr_export_default__' before initialization]`,
+    )
+  })
 })
 
 describe('optimize-deps', async () => {
diff --git a/packages/vite/src/node/ssr/ssrTransform.ts b/packages/vite/src/node/ssr/ssrTransform.ts
@@ -318,17 +318,16 @@ async function ssrTransformScript(
         // export default class A {}
         const { name } = node.declaration.id
         s.remove(node.start, node.start + 15 /* 'export default '.length */)
-        s.append(
-          `\nObject.defineProperty(${ssrModuleExportsKey}, "default", ` +
-            `{ enumerable: true, configurable: true, value: ${name} });`,
-        )
+        defineExport('default', name)
       } else {
         // anonymous default exports
+        const name = `__vite_ssr_export_default__`
         s.update(
           node.start,
           node.start + 14 /* 'export default'.length */,
-          `${ssrModuleExportsKey}.default =`,
+          `const ${name} =`,
         )
+        defineExport('default', name)
       }
     }
 
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml

Original file line number	Diff line number	Diff line change
`@@ -235,7 +235,7 @@ test('json', async () => {`
`235`	`235`	`null,`
`236`	`236`	`'/test.json',`
`237`	`237`	`)`
`238`		- expect(json?.code.length).toMatchInlineSnapshot(`61`)
	`238`	+ expect(json?.code.length).toMatchInlineSnapshot(`208`)
`239`	`239`	`})`
`240`	`240`
`241`	`241`	`test('file url', async () => {`
Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,2 @@`
	`1`	`+import dep from "./index.js"`
	`2`	`+export default dep`
Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,2 @@`
	`1`	`+import dep from "./dep.js";`
	`2`	`+export default dep`