feat: defineExpose() support

packages/compiler-sfc/src/compileScript.ts

@@ -1183,7 +1183,7 @@ export function compileScript(
     s.prependLeft(startOffset, `\nlet __temp${any}, __restore${any}\n`)
   }
 
-  const destructureElements = [`expose`]
+  const destructureElements = hasDefineExposeCall ? [`expose`] : []
   if (emitIdentifier) {
     destructureElements.push(
       emitIdentifier === `emit` ? `emit` : `emit: ${emitIdentifier}`
@@ -1256,9 +1256,6 @@ export function compileScript(
     runtimeOptions += genRuntimeEmits(typeDeclaredEmits)
   }
 
-  // <script setup> components are closed by default. If the user did not
-  // explicitly call `defineExpose`, call expose() with no args.
-  const exposeCall = hasDefineExposeCall ? `` : `  expose();\n`
   // wrap setup code with function.
   if (isTS) {
     // for TS, make sure the exported type is still valid type with
@@ -1273,7 +1270,7 @@ export function compileScript(
         `defineComponent`
       )}({${def}${runtimeOptions}\n  ${
         hasAwait ? `async ` : ``
-      }setup(${args}) {\n${exposeCall}`
+      }setup(${args}) {\n`
     )
     s.appendRight(endOffset, `})`)
   } else {
@@ -1283,14 +1280,14 @@ export function compileScript(
       s.prependLeft(
         startOffset,
         `\nexport default /*#__PURE__*/Object.assign(${DEFAULT_VAR}, {${runtimeOptions}\n  ` +
-          `${hasAwait ? `async ` : ``}setup(${args}) {\n${exposeCall}`
+          `${hasAwait ? `async ` : ``}setup(${args}) {\n`
       )
       s.appendRight(endOffset, `})`)
     } else {
       s.prependLeft(
         startOffset,
         `\nexport default {${runtimeOptions}\n  ` +
-          `${hasAwait ? `async ` : ``}setup(${args}) {\n${exposeCall}`
+          `${hasAwait ? `async ` : ``}setup(${args}) {\n`
       )
       s.appendRight(endOffset, `}`)
     }

packages/compiler-sfc/test/__snapshots__/compileScript.spec.ts.snap

@@ -3,8 +3,7 @@
 exports[`SFC analyze <script> bindings > auto name inference > basic 1`] = `
 "export default {
   __name: 'FooBar',
-  setup(__props, { expose }) {
+  setup(__props) {
-  expose();
 const a = 1
 return { a }
 }
@@ -19,8 +18,7 @@ exports[`SFC analyze <script> bindings > auto name inference > do not overwrite
         })
         
 export default /*#__PURE__*/Object.assign(__default__, {
-  setup(__props, { expose }) {
+  setup(__props) {
-  expose();
 const a = 1
 return { a, defineComponent }
 }
@@ -34,8 +32,7 @@ exports[`SFC analyze <script> bindings > auto name inference > do not overwrite
         }
         
 export default /*#__PURE__*/Object.assign(__default__, {
-  setup(__props, { expose }) {
+  setup(__props) {
-  expose();
 const a = 1
 return { a }
 }
@@ -48,8 +45,7 @@ exports[`SFC compile <script setup> > <script> after <script setup> the script c
 import { x } from './x'
     
 export default {
-  setup(__props, { expose }) {
+  setup(__props) {
-  expose();
 
     
 return { n, x }
@@ -66,8 +62,7 @@ exports[`SFC compile <script setup> > <script> and <script setup> co-usage > scr
       const __default__ = {}
       
 export default /*#__PURE__*/Object.assign(__default__, {
-  setup(__props, { expose }) {
+  setup(__props) {
-  expose();
 
       x()
       
@@ -84,8 +79,7 @@ exports[`SFC compile <script setup> > <script> and <script setup> co-usage > scr
 import { x } from './x'
       
 export default /*#__PURE__*/Object.assign(__default__, {
-  setup(__props, { expose }) {
+  setup(__props) {
-  expose();
 
       x()
       
@@ -106,8 +100,7 @@ import { x } from './x'
       
 export default /*#__PURE__*/_defineComponent({
   ...__default__,
-  setup(__props, { expose }) {
+  setup(__props) {
-  expose();
 
       x()
       
@@ -127,8 +120,7 @@ const __default__ = def
 import { x } from './x'
       
 export default /*#__PURE__*/Object.assign(__default__, {
-  setup(__props, { expose }) {
+  setup(__props) {
-  expose();
 
       x()
       
@@ -147,8 +139,7 @@ exports[`SFC compile <script setup> > <script> and <script setup> co-usage > spa
         }
         
 export default /*#__PURE__*/Object.assign(__default__, {
-  setup(__props, { expose }) {
+  setup(__props) {
-  expose();
 
         x()
         
@@ -167,8 +158,7 @@ exports[`SFC compile <script setup> > <script> and <script setup> co-usage > spa
         }
         
 export default /*#__PURE__*/Object.assign(__default__, {
-  setup(__props, { expose }) {
+  setup(__props) {
-  expose();
 
         x()
         
@@ -182,8 +172,7 @@ exports[`SFC compile <script setup> > async/await detection > expression stateme
 "import { withAsyncContext as _withAsyncContext } from 'vue'
 
 export default {
-  async setup(__props, { expose }) {
+  async setup(__props) {
-  expose();
 
 let __temp, __restore
 ;(
@@ -201,8 +190,7 @@ exports[`SFC compile <script setup> > async/await detection > multiple \`if for\
 "import { withAsyncContext as _withAsyncContext } from 'vue'
 
 export default {
-  async setup(__props, { expose }) {
+  async setup(__props) {
-  expose();
 
 let __temp, __restore
 if (ok) {
@@ -236,8 +224,7 @@ exports[`SFC compile <script setup> > async/await detection > multiple \`if whil
 "import { withAsyncContext as _withAsyncContext } from 'vue'
 
 export default {
-  async setup(__props, { expose }) {
+  async setup(__props) {
-  expose();
 
 let __temp, __restore
 if (ok) {
@@ -291,8 +278,7 @@ exports[`SFC compile <script setup> > async/await detection > multiple \`if\` ne
 "import { withAsyncContext as _withAsyncContext } from 'vue'
 
 export default {
-  async setup(__props, { expose }) {
+  async setup(__props) {
-  expose();
 
 let __temp, __restore
 if (ok) {
@@ -368,8 +354,7 @@ exports[`SFC compile <script setup> > async/await detection > nested await 1`] =
 "import { withAsyncContext as _withAsyncContext } from 'vue'
 
 export default {
-  async setup(__props, { expose }) {
+  async setup(__props) {
-  expose();
 
 let __temp, __restore
 ;(
@@ -392,8 +377,7 @@ exports[`SFC compile <script setup> > async/await detection > nested await 2`] =
 "import { withAsyncContext as _withAsyncContext } from 'vue'
 
 export default {
-  async setup(__props, { expose }) {
+  async setup(__props) {
-  expose();
 
 let __temp, __restore
 ;(
@@ -416,8 +400,7 @@ exports[`SFC compile <script setup> > async/await detection > nested await 3`] =
 "import { withAsyncContext as _withAsyncContext } from 'vue'
 
 export default {
-  async setup(__props, { expose }) {
+  async setup(__props) {
-  expose();
 
 let __temp, __restore
 ;(
@@ -445,8 +428,7 @@ exports[`SFC compile <script setup> > async/await detection > nested leading awa
 "import { withAsyncContext as _withAsyncContext } from 'vue'
 
 export default {
-  async setup(__props, { expose }) {
+  async setup(__props) {
-  expose();
 
 let __temp, __restore
 foo()
@@ -471,8 +453,7 @@ exports[`SFC compile <script setup> > async/await detection > nested statements
 "import { withAsyncContext as _withAsyncContext } from 'vue'
 
 export default {
-  async setup(__props, { expose }) {
+  async setup(__props) {
-  expose();
 
 let __temp, __restore
 if (ok) { (
@@ -494,8 +475,7 @@ exports[`SFC compile <script setup> > async/await detection > ref 1`] = `
 "import { withAsyncContext as _withAsyncContext } from 'vue'
 
 export default {
-  async setup(__props, { expose }) {
+  async setup(__props) {
-  expose();
 
 let __temp, __restore
 let a = $ref(1 + ((
@@ -512,8 +492,7 @@ return { a }
 
 exports[`SFC compile <script setup> > async/await detection > should ignore await inside functions 1`] = `
 "export default {
-  setup(__props, { expose }) {
+  setup(__props) {
-  expose();
 async function foo() { await bar }
 return { foo }
 }
@@ -523,8 +502,7 @@ return { foo }
 
 exports[`SFC compile <script setup> > async/await detection > should ignore await inside functions 2`] = `
 "export default {
-  setup(__props, { expose }) {
+  setup(__props) {
-  expose();
 const foo = async () => { await bar }
 return { foo }
 }
@@ -534,8 +512,7 @@ return { foo }
 
 exports[`SFC compile <script setup> > async/await detection > should ignore await inside functions 3`] = `
 "export default {
-  setup(__props, { expose }) {
+  setup(__props) {
-  expose();
 const obj = { async method() { await bar }}
 return { obj }
 }
@@ -545,8 +522,7 @@ return { obj }
 
 exports[`SFC compile <script setup> > async/await detection > should ignore await inside functions 4`] = `
 "export default {
-  setup(__props, { expose }) {
+  setup(__props) {
-  expose();
 const cls = class Foo { async method() { await bar }}
 return { cls }
 }
@@ -558,8 +534,7 @@ exports[`SFC compile <script setup> > async/await detection > single line condit
 "import { withAsyncContext as _withAsyncContext } from 'vue'
 
 export default {
-  async setup(__props, { expose }) {
+  async setup(__props) {
-  expose();
 
 let __temp, __restore
 if (false) (
@@ -577,8 +552,7 @@ exports[`SFC compile <script setup> > async/await detection > variable 1`] = `
 "import { withAsyncContext as _withAsyncContext } from 'vue'
 
 export default {
-  async setup(__props, { expose }) {
+  async setup(__props) {
-  expose();
 
 let __temp, __restore
 const a = 1 + ((
@@ -595,8 +569,7 @@ return { a }
 
 exports[`SFC compile <script setup> > binding analysis for destructure 1`] = `
 "export default {
-  setup(__props, { expose }) {
+  setup(__props) {
-  expose();
 
       const { foo, b: bar, ['x' + 'y']: baz, x: { y, zz: { z }}} = {}
       
@@ -609,8 +582,7 @@ return { foo, bar, baz, y, z }
 exports[`SFC compile <script setup> > defineEmits() 1`] = `
 "export default {
   emits: ['foo', 'bar'],
-  setup(__props, { expose, emit: myEmit }) {
+  setup(__props, { emit: myEmit }) {
-  expose();
 
 
 
@@ -637,8 +609,7 @@ exports[`SFC compile <script setup> > defineProps w/ external definition 1`] = `
     
 export default {
   props: propsModel,
-  setup(__props, { expose }) {
+  setup(__props) {
-  expose();
 
 const props = __props
 
@@ -655,8 +626,7 @@ exports[`SFC compile <script setup> > defineProps w/ leading code 1`] = `
     
 export default {
   props: {},
-  setup(__props, { expose }) {
+  setup(__props) {
-  expose();
 
 const props = __props
 
@@ -672,8 +642,7 @@ exports[`SFC compile <script setup> > defineProps() 1`] = `
   props: {
   foo: String
 },
-  setup(__props, { expose }) {
+  setup(__props) {
-  expose();
 
 const props = __props
 
@@ -690,8 +659,7 @@ exports[`SFC compile <script setup> > defineProps/defineEmits in multi-variable
 "export default {
   props: ['item'],
   emits: ['a'],
-  setup(__props, { expose, emit }) {
+  setup(__props, { emit }) {
-  expose();
 
 const props = __props
 
@@ -707,8 +675,7 @@ exports[`SFC compile <script setup> > defineProps/defineEmits in multi-variable
 "export default {
   props: ['item'],
   emits: ['a'],
-  setup(__props, { expose, emit }) {
+  setup(__props, { emit }) {
-  expose();
 
 const props = __props
 
@@ -725,8 +692,7 @@ exports[`SFC compile <script setup> > dev mode import usage check > TS annotatio
 import { Foo, Baz, Qux, Fred } from './x'
         
 export default /*#__PURE__*/_defineComponent({
-  setup(__props, { expose }) {
+  setup(__props) {
-  expose();
 
         const a = 1
         function b() {}
@@ -742,8 +708,7 @@ exports[`SFC compile <script setup> > dev mode import usage check > attribute ex
 import { bar, baz } from './x'
         
 export default /*#__PURE__*/_defineComponent({
-  setup(__props, { expose }) {
+  setup(__props) {
-  expose();
 
         const cond = true
         
@@ -758,8 +723,7 @@ exports[`SFC compile <script setup> > dev mode import usage check > components 1
 import { FooBar, FooBaz, FooQux, foo } from './x'
         
 export default /*#__PURE__*/_defineComponent({
-  setup(__props, { expose }) {
+  setup(__props) {
-  expose();
 
         const fooBar: FooBar = 1
         
@@ -774,8 +738,7 @@ exports[`SFC compile <script setup> > dev mode import usage check > directive 1`
 import { vMyDir } from './x'
         
 export default /*#__PURE__*/_defineComponent({
-  setup(__props, { expose }) {
+  setup(__props) {
-  expose();
 
         
 return { vMyDir }
@@ -789,8 +752,7 @@ exports[`SFC compile <script setup> > dev mode import usage check > js template
 import { VAR, VAR2, VAR3 } from './x'
         
 export default /*#__PURE__*/_defineComponent({
-  setup(__props, { expose }) {
+  setup(__props) {
-  expose();
 
         
 return { VAR, VAR3 }
@@ -804,8 +766,7 @@ exports[`SFC compile <script setup> > dev mode import usage check > last tag 1`]
 import { FooBaz, Last } from './x'
         
 export default /*#__PURE__*/_defineComponent({
-  setup(__props, { expose }) {
+  setup(__props) {
-  expose();
 
         
 return { FooBaz, Last }
@@ -819,8 +780,7 @@ exports[`SFC compile <script setup> > dev mode import usage check > vue interpol
 import { x, y, z, x$y } from './x'
       
 export default /*#__PURE__*/_defineComponent({
-  setup(__props, { expose }) {
+  setup(__props) {
-  expose();
 
       
 return { x, z, x$y }
@@ -841,8 +801,7 @@ export default {
   emits: {
           foo: () => bar > 1
         },
-  setup(__props, { expose }) {
+  setup(__props) {
-  expose();
 
         
         
@@ -863,8 +822,7 @@ exports[`SFC compile <script setup> > errors > should allow defineProps/Emit() r
   emits: {
             foo: bar => bar > 1
           },
-  setup(__props, { expose }) {
+  setup(__props) {
-  expose();
 
           const bar = 1
           
@@ -880,8 +838,7 @@ exports[`SFC compile <script setup> > imports > import dedupe between <script> a
 "import { x } from './x'
         
 export default {
-  setup(__props, { expose }) {
+  setup(__props) {
-  expose();
 
         x()
         
@@ -897,8 +854,7 @@ exports[`SFC compile <script setup> > imports > should allow defineProps/Emit at
 export default {
   props: ['foo'],
   emits: ['bar'],
-  setup(__props, { expose }) {
+  setup(__props) {
-  expose();
 
       
       
@@ -915,8 +871,7 @@ exports[`SFC compile <script setup> > imports > should extract comment for impor
         import b from 'b'
         
 export default {
-  setup(__props, { expose }) {
+  setup(__props) {
-  expose();
 
         
 return { a, b }
@@ -930,8 +885,7 @@ exports[`SFC compile <script setup> > imports > should hoist and expose imports
           import 'foo/css'
         
 export default {
-  setup(__props, { expose }) {
+  setup(__props) {
-  expose();
 
           
 return { ref }
@@ -950,8 +904,7 @@ exports[`SFC compile <script setup> > should expose top level declarations 1`] =
 import { x } from './x'
       
 export default {
-  setup(__props, { expose }) {
+  setup(__props) {
-  expose();
 
       let a = 1
       const b = 2
@@ -969,8 +922,7 @@ exports[`SFC compile <script setup> > with TypeScript > const Enum 1`] = `
 const enum Foo { A = 123 }
         
 export default /*#__PURE__*/_defineComponent({
-  setup(__props, { expose }) {
+  setup(__props) {
-  expose();
 
         
 return { Foo }
@@ -985,8 +937,7 @@ export interface Emits { (e: 'foo' | 'bar'): void }
       
 export default /*#__PURE__*/_defineComponent({
   emits: [\\"foo\\", \\"bar\\"],
-  setup(__props, { expose, emit }: { emit: ({ (e: 'foo' | 'bar'): void }), expose: any, slots: any, attrs: any }) {
+  setup(__props, { emit }: { emit: ({ (e: 'foo' | 'bar'): void }), expose: any, slots: any, attrs: any }) {
-  expose();
 
       
       
@@ -1002,8 +953,7 @@ export type Emits = { (e: 'foo' | 'bar'): void }
       
 export default /*#__PURE__*/_defineComponent({
   emits: [\\"foo\\", \\"bar\\"],
-  setup(__props, { expose, emit }: { emit: ({ (e: 'foo' | 'bar'): void }), expose: any, slots: any, attrs: any }) {
+  setup(__props, { emit }: { emit: ({ (e: 'foo' | 'bar'): void }), expose: any, slots: any, attrs: any }) {
-  expose();
 
       
       
@@ -1019,8 +969,7 @@ interface Emits { (e: 'foo' | 'bar'): void }
       
 export default /*#__PURE__*/_defineComponent({
   emits: [\\"foo\\", \\"bar\\"],
-  setup(__props, { expose, emit }: { emit: ({ (e: 'foo' | 'bar'): void }), expose: any, slots: any, attrs: any }) {
+  setup(__props, { emit }: { emit: ({ (e: 'foo' | 'bar'): void }), expose: any, slots: any, attrs: any }) {
-  expose();
 
       
       
@@ -1036,8 +985,7 @@ export type Emits = (e: 'foo' | 'bar') => void
       
 export default /*#__PURE__*/_defineComponent({
   emits: [\\"foo\\", \\"bar\\"],
-  setup(__props, { expose, emit }: { emit: ((e: 'foo' | 'bar') => void), expose: any, slots: any, attrs: any }) {
+  setup(__props, { emit }: { emit: ((e: 'foo' | 'bar') => void), expose: any, slots: any, attrs: any }) {
-  expose();
 
       
       
@@ -1053,8 +1001,7 @@ type Emits = (e: 'foo' | 'bar') => void
       
 export default /*#__PURE__*/_defineComponent({
   emits: [\\"foo\\", \\"bar\\"],
-  setup(__props, { expose, emit }: { emit: ((e: 'foo' | 'bar') => void), expose: any, slots: any, attrs: any }) {
+  setup(__props, { emit }: { emit: ((e: 'foo' | 'bar') => void), expose: any, slots: any, attrs: any }) {
-  expose();
 
       
       
@@ -1070,8 +1017,7 @@ type Emits = { (e: 'foo' | 'bar'): void }
       
 export default /*#__PURE__*/_defineComponent({
   emits: [\\"foo\\", \\"bar\\"],
-  setup(__props, { expose, emit }: { emit: ({ (e: 'foo' | 'bar'): void }), expose: any, slots: any, attrs: any }) {
+  setup(__props, { emit }: { emit: ({ (e: 'foo' | 'bar'): void }), expose: any, slots: any, attrs: any }) {
-  expose();
 
       
       
@@ -1086,8 +1032,7 @@ exports[`SFC compile <script setup> > with TypeScript > defineEmits w/ type (typ
 
 export default /*#__PURE__*/_defineComponent({
   emits: [\\"foo\\", \\"bar\\", \\"baz\\"],
-  setup(__props, { expose, emit }: { emit: ({(e: 'foo' | 'bar'): void; (e: 'baz', id: number): void;}), expose: any, slots: any, attrs: any }) {
+  setup(__props, { emit }: { emit: ({(e: 'foo' | 'bar'): void; (e: 'baz', id: number): void;}), expose: any, slots: any, attrs: any }) {
-  expose();
 
       
       
@@ -1102,8 +1047,7 @@ exports[`SFC compile <script setup> > with TypeScript > defineEmits w/ type 1`]
 
 export default /*#__PURE__*/_defineComponent({
   emits: [\\"foo\\", \\"bar\\"],
-  setup(__props, { expose, emit }: { emit: ((e: 'foo' | 'bar') => void), expose: any, slots: any, attrs: any }) {
+  setup(__props, { emit }: { emit: ((e: 'foo' | 'bar') => void), expose: any, slots: any, attrs: any }) {
-  expose();
 
       
       
@@ -1121,8 +1065,7 @@ export default /*#__PURE__*/_defineComponent({
   props: {
     x: { type: Number, required: false }
   },
-  setup(__props: any, { expose }) {
+  setup(__props: any) {
-  expose();
 
       
       
@@ -1141,8 +1084,7 @@ export default /*#__PURE__*/_defineComponent({
   props: {
     x: { type: Number, required: false }
   },
-  setup(__props: any, { expose }) {
+  setup(__props: any) {
-  expose();
 
         
       
@@ -1160,8 +1102,7 @@ export default /*#__PURE__*/_defineComponent({
   props: {
     x: { type: Number, required: false }
   },
-  setup(__props: any, { expose }) {
+  setup(__props: any) {
-  expose();
 
       
       
@@ -1179,8 +1120,7 @@ export default /*#__PURE__*/_defineComponent({
   props: {
     x: { type: Number, required: false }
   },
-  setup(__props: any, { expose }) {
+  setup(__props: any) {
-  expose();
 
       
       
@@ -1226,8 +1166,7 @@ export default /*#__PURE__*/_defineComponent({
     intersection: { type: Object, required: true },
     foo: { type: [Function, null], required: true }
   },
-  setup(__props: any, { expose }) {
+  setup(__props: any) {
-  expose();
 
       
       
@@ -1245,8 +1184,7 @@ export default /*#__PURE__*/_defineComponent({
   props: {
     x: { type: Number, required: false }
   },
-  setup(__props: any, { expose }) {
+  setup(__props: any) {
-  expose();
 
       
       
@@ -1262,8 +1200,7 @@ exports[`SFC compile <script setup> > with TypeScript > defineProps/Emit w/ runt
 export default /*#__PURE__*/_defineComponent({
   props: { foo: String },
   emits: ['a', 'b'],
-  setup(__props, { expose, emit }) {
+  setup(__props, { emit }) {
-  expose();
 
 const props = __props
 
@@ -1282,8 +1219,7 @@ export interface Foo {}
         type Bar = {}
       
 export default /*#__PURE__*/_defineComponent({
-  setup(__props, { expose }) {
+  setup(__props) {
-  expose();
 
         
 return {  }
@@ -1298,8 +1234,7 @@ import type { Foo } from './main.ts'
         import { type Bar, Baz } from './main.ts'
         
 export default /*#__PURE__*/_defineComponent({
-  setup(__props, { expose }) {
+  setup(__props) {
-  expose();
 
         
 return { Baz }
@@ -1313,8 +1248,7 @@ exports[`SFC compile <script setup> > with TypeScript > runtime Enum 1`] = `
 enum Foo { A = 123 }
         
 export default /*#__PURE__*/_defineComponent({
-  setup(__props, { expose }) {
+  setup(__props) {
-  expose();
 
         
 return { Foo }
@@ -1332,8 +1266,7 @@ enum Foo { A = 123 }
           enum B { B = \\"B\\" }
         
 export default /*#__PURE__*/_defineComponent({
-  setup(__props, { expose }) {
+  setup(__props) {
-  expose();
 
         
 return { D, C, B, Foo }
@@ -1352,8 +1285,7 @@ export default /*#__PURE__*/_defineComponent({
     bar: { type: Number, required: false },
     baz: { type: Boolean, required: true }
   }, { ...defaults }),
-  setup(__props: any, { expose }) {
+  setup(__props: any) {
-  expose();
 
 const props = __props as {
         foo?: string
@@ -1379,8 +1311,7 @@ export default /*#__PURE__*/_defineComponent({
     baz: { type: Boolean, required: true },
     qux: { type: Function, required: false, default() { return 1 } }
   },
-  setup(__props: any, { expose }) {
+  setup(__props: any) {
-  expose();
 
 const props = __props as { foo: string, bar?: number, baz: boolean, qux(): number }
 

packages/compiler-sfc/test/compileScript.spec.ts

@@ -102,7 +102,7 @@ const bar = 1
     // should remove defineOptions import and call
     expect(content).not.toMatch('defineProps')
     // should generate correct setup signature
-    expect(content).toMatch(`setup(__props, { expose }) {`)
+    expect(content).toMatch(`setup(__props) {`)
     // should assign user identifier to it
     expect(content).toMatch(`const props = __props`)
     // should include context options in default export
@@ -149,7 +149,7 @@ const myEmit = defineEmits(['foo', 'bar'])
     // should remove defineOptions import and call
     expect(content).not.toMatch('defineEmits')
     // should generate correct setup signature
-    expect(content).toMatch(`setup(__props, { expose, emit: myEmit }) {`)
+    expect(content).toMatch(`setup(__props, { emit: myEmit }) {`)
     // should include context options in default export
     expect(content).toMatch(`export default {
   emits: ['foo', 'bar'],`)
@@ -769,7 +769,7 @@ const emit = defineEmits(['a', 'b'])
       expect(content).toMatch(`export default /*#__PURE__*/_defineComponent({
   props: { foo: String },
   emits: ['a', 'b'],
-  setup(__props, { expose, emit }) {`)
+  setup(__props, { emit }) {`)
     })
 
     test('defineProps w/ type', () => {

src/core/config.ts

@@ -13,8 +13,8 @@ export interface Config {
   productionTip: boolean
   performance: boolean
   devtools: boolean
-  errorHandler?: (err: Error, vm: Component, info: string) => void
+  errorHandler?: (err: Error, vm: Component | null, info: string) => void
-  warnHandler?: (msg: string, vm: Component, trace: string) => void
+  warnHandler?: (msg: string, vm: Component | null, trace: string) => void
   ignoredElements: Array<string | RegExp>
   keyCodes: { [key: string]: number | Array<number> }
 

src/core/util/debug.ts

@@ -3,7 +3,7 @@ import { noop, isArray, isFunction } from 'shared/util'
 import type { Component } from 'types/component'
 import { currentInstance } from 'v3/currentInstance'
 
-export let warn = noop
+export let warn: (msg: string, vm?: Component | null) => void = noop
 export let tip = noop
 export let generateComponentTrace: (vm: Component) => string // work around flow check
 export let formatComponentName: (vm: Component, includeFile?: false) => string

src/types/options.ts

@@ -90,7 +90,7 @@ export type ComponentOptions = {
   comments?: boolean
   inheritAttrs?: boolean
 
-  // Class API
+  // Legacy API
   abstract?: any
 
   // private

src/v3/apiSetup.ts

@@ -12,6 +12,7 @@ export interface SetupContext {
   attrs: Record<string, any>
   slots: Record<string, () => VNode[]>
   emit: (event: string, ...args: any[]) => any
+  expose: (exposed: Record<string, any>) => void
 }
 
 export function initSetup(vm: Component) {
@@ -47,7 +48,7 @@ export function initSetup(vm: Component) {
       if (!setupResult.__sfc) {
         for (const key in setupResult) {
           if (!isReserved(key)) {
-            proxySetupProperty(vm, setupResult, key)
+            proxyWithRefUnwrap(vm, setupResult, key)
           } else if (__DEV__) {
             warn(`Avoid using variables that start with _ or $ in setup().`)
           }
@@ -56,7 +57,7 @@ export function initSetup(vm: Component) {
         // exposed for compiled render fn
         const proxy = (vm._setupProxy = {})
         for (const key in setupResult) {
-          proxySetupProperty(proxy, setupResult, key)
+          proxyWithRefUnwrap(proxy, setupResult, key)
         }
       }
     } else if (__DEV__ && setupResult !== undefined) {
@@ -69,22 +70,23 @@ export function initSetup(vm: Component) {
   }
 }
 
-function proxySetupProperty(
+export function proxyWithRefUnwrap(
   target: any,
-  setupResult: Record<string, any>,
+  source: Record<string, any>,
   key: string
 ) {
-  let raw = setupResult[key]
+  let raw = source[key]
   Object.defineProperty(target, key, {
     enumerable: true,
     configurable: true,
     get: () => (isRef(raw) ? raw.value : raw),
     set: newVal =>
-      isRef(raw) ? (raw.value = newVal) : (raw = setupResult[key] = newVal)
+      isRef(raw) ? (raw.value = newVal) : (raw = source[key] = newVal)
   })
 }
 
-function createSetupContext(vm: Component) {
+function createSetupContext(vm: Component): SetupContext {
+  let exposeCalled = false
   return {
     get attrs() {
       return initAttrsProxy(vm)
@@ -93,8 +95,18 @@ function createSetupContext(vm: Component) {
       return initSlotsProxy(vm)
     },
     emit: bind(vm.$emit, vm) as any,
-    expose() {
+    expose(exposed?: Record<string, any>) {
-      // TODO
+      if (__DEV__) {
+        if (exposeCalled) {
+          warn(`expose() should be called only once per setup().`, vm)
+        }
+        exposeCalled = true
+      }
+      if (exposed) {
+        Object.keys(exposed).forEach(key =>
+          proxyWithRefUnwrap(vm, exposed, key)
+        )
+      }
     }
   }
 }