feat(compiler-sfc): analyze import usage in template via AST

packages/compiler-core/__tests__/parse.spec.ts

@@ -14,6 +14,7 @@ import {
 } from '../src/ast'
 
 import { baseParse } from '../src/parser'
+import { Program } from '@babel/types'
 
 /* eslint jest/no-disabled-tests: "off" */
 
@@ -2170,6 +2171,63 @@ describe('compiler: parse', () => {
     })
   })
 
+  describe('expression parsing', () => {
+    test('interpolation', () => {
+      const ast = baseParse(`{{ a + b }}`, { prefixIdentifiers: true })
+      // @ts-ignore
+      expect((ast.children[0] as InterpolationNode).content.ast?.type).toBe(
+        'BinaryExpression'
+      )
+    })
+
+    test('v-bind', () => {
+      const ast = baseParse(`<div :[key+1]="foo()" />`, {
+        prefixIdentifiers: true
+      })
+      const dir = (ast.children[0] as ElementNode).props[0] as DirectiveNode
+      // @ts-ignore
+      expect(dir.arg?.ast?.type).toBe('BinaryExpression')
+      // @ts-ignore
+      expect(dir.exp?.ast?.type).toBe('CallExpression')
+    })
+
+    test('v-on multi statements', () => {
+      const ast = baseParse(`<div @click="a++;b++" />`, {
+        prefixIdentifiers: true
+      })
+      const dir = (ast.children[0] as ElementNode).props[0] as DirectiveNode
+      // @ts-ignore
+      expect(dir.exp?.ast?.type).toBe('Program')
+      expect((dir.exp?.ast as Program).body).toMatchObject([
+        { type: 'ExpressionStatement' },
+        { type: 'ExpressionStatement' }
+      ])
+    })
+
+    test('v-slot', () => {
+      const ast = baseParse(`<Comp #foo="{ a, b }" />`, {
+        prefixIdentifiers: true
+      })
+      const dir = (ast.children[0] as ElementNode).props[0] as DirectiveNode
+      // @ts-ignore
+      expect(dir.exp?.ast?.type).toBe('ArrowFunctionExpression')
+    })
+
+    test('v-for', () => {
+      const ast = baseParse(`<div v-for="({ a, b }, key, index) of a.b" />`, {
+        prefixIdentifiers: true
+      })
+      const dir = (ast.children[0] as ElementNode).props[0] as DirectiveNode
+      const { source, value, key, index } = dir.forParseResult!
+      // @ts-ignore
+      expect(source.ast?.type).toBe('MemberExpression')
+      // @ts-ignore
+      expect(value?.ast?.type).toBe('ArrowFunctionExpression')
+      expect(key?.ast).toBeNull() // simple ident
+      expect(index?.ast).toBeNull() // simple ident
+    })
+  })
+
   describe('Errors', () => {
     // HTML parsing errors as specified at
     // https://html.spec.whatwg.org/multipage/parsing.html#parse-errors

packages/compiler-core/__tests__/transforms/transformExpressions.spec.ts

@@ -18,7 +18,7 @@ function parseWithExpressionTransform(
   template: string,
   options: CompilerOptions = {}
 ) {
-  const ast = parse(template)
+  const ast = parse(template, options)
   transform(ast, {
     prefixIdentifiers: true,
     nodeTransforms: [transformIf, transformExpression],

packages/compiler-core/src/ast.ts

@@ -14,6 +14,7 @@ import {
 } from './runtimeHelpers'
 import { PropsExpression } from './transforms/transformElement'
 import { ImportItem, TransformContext } from './transform'
+import { Node as BabelNode } from '@babel/types'
 
 // Vue template is a platform-agnostic superset of HTML (syntax only).
 // More namespaces can be declared by platform specific compilers.
@@ -226,6 +227,12 @@ export interface SimpleExpressionNode extends Node {
   content: string
   isStatic: boolean
   constType: ConstantTypes
+  /**
+   * - `null` means the expression is a simple identifier that doesn't need
+   *    parsing
+   * - `false` means there was a parsing error
+   */
+  ast?: BabelNode | null | false
   /**
    * Indicates this is an identifier for a hoist vnode call and points to the
    * hoisted node.
@@ -246,6 +253,12 @@ export interface InterpolationNode extends Node {
 
 export interface CompoundExpressionNode extends Node {
   type: NodeTypes.COMPOUND_EXPRESSION
+  /**
+   * - `null` means the expression is a simple identifier that doesn't need
+   *    parsing
+   * - `false` means there was a parsing error
+   */
+  ast?: BabelNode | null | false
   children: (
     | SimpleExpressionNode
     | CompoundExpressionNode

packages/compiler-core/src/babelUtils.ts

@@ -28,9 +28,9 @@ export function walkIdentifiers(
   }
 
   const rootExp =
-    root.type === 'Program' &&
-    root.body[0].type === 'ExpressionStatement' &&
-    root.body[0].expression
+    root.type === 'Program'
+      ? root.body[0].type === 'ExpressionStatement' && root.body[0].expression
+      : root
 
   walk(root, {
     enter(node: Node & { scopeIds?: Set<string> }, parent: Node | undefined) {

packages/compiler-core/src/options.ts

@@ -86,6 +86,17 @@ export interface ParserOptions
    * This defaults to `true` in development and `false` in production builds.
    */
   comments?: boolean
+  /**
+   * Parse JavaScript expressions with Babel.
+   * @default false
+   */
+  prefixIdentifiers?: boolean
+  /**
+   * A list of parser plugins to enable for `@babel/parser`, which is used to
+   * parse expressions in bindings and interpolations.
+   * https://babeljs.io/docs/en/next/babel-parser#plugins
+   */
+  expressionPlugins?: ParserPlugin[]
 }
 
 export type HoistTransform = (

packages/compiler-core/src/parser.ts

@@ -38,14 +38,25 @@ import {
   defaultOnError,
   defaultOnWarn
 } from './errors'
-import { forAliasRE, isCoreComponent, isStaticArgOf } from './utils'
+import {
+  forAliasRE,
+  isCoreComponent,
+  isSimpleIdentifier,
+  isStaticArgOf
+} from './utils'
 import { decodeHTML } from 'entities/lib/decode.js'
+import {
+  parse,
+  parseExpression,
+  type ParserOptions as BabelOptions
+} from '@babel/parser'
 
 type OptionalOptions =
   | 'decodeEntities'
   | 'whitespace'
   | 'isNativeTag'
   | 'isBuiltInComponent'
+  | 'expressionPlugins'
   | keyof CompilerCompatOptions
 
 export type MergedParserOptions = Omit<
@@ -64,7 +75,8 @@ export const defaultParserOptions: MergedParserOptions = {
   isCustomElement: NO,
   onError: defaultOnError,
   onWarn: defaultOnWarn,
-  comments: __DEV__
+  comments: __DEV__,
+  prefixIdentifiers: false
 }
 
 let currentOptions: MergedParserOptions = defaultParserOptions
@@ -116,7 +128,7 @@ const tokenizer = new Tokenizer(stack, {
     }
     addNode({
       type: NodeTypes.INTERPOLATION,
-      content: createSimpleExpression(exp, false, getLoc(innerStart, innerEnd)),
+      content: createExp(exp, false, getLoc(innerStart, innerEnd)),
       loc: getLoc(start, end)
     })
   },
@@ -245,7 +257,7 @@ const tokenizer = new Tokenizer(stack, {
       setLocEnd((currentProp as AttributeNode).nameLoc, end)
     } else {
       const isStatic = arg[0] !== `[`
-      ;(currentProp as DirectiveNode).arg = createSimpleExpression(
+      ;(currentProp as DirectiveNode).arg = createExp(
         isStatic ? arg : arg.slice(1, -1),
         isStatic,
         getLoc(start, end),
@@ -346,10 +358,25 @@ const tokenizer = new Tokenizer(stack, {
           }
         } else {
           // directive
-          currentProp.exp = createSimpleExpression(
+          let expParseMode = ExpParseMode.Normal
+          if (!__BROWSER__) {
+            if (currentProp.name === 'for') {
+              expParseMode = ExpParseMode.Skip
+            } else if (currentProp.name === 'slot') {
+              expParseMode = ExpParseMode.Params
+            } else if (
+              currentProp.name === 'on' &&
+              currentAttrValue.includes(';')
+            ) {
+              expParseMode = ExpParseMode.Statements
+            }
+          }
+          currentProp.exp = createExp(
             currentAttrValue,
             false,
-            getLoc(currentAttrStartIndex, currentAttrEndIndex)
+            getLoc(currentAttrStartIndex, currentAttrEndIndex),
+            ConstantTypes.NOT_CONSTANT,
+            expParseMode
           )
           if (currentProp.name === 'for') {
             currentProp.forParseResult = parseForExpression(currentProp.exp)
@@ -477,10 +504,20 @@ function parseForExpression(
 
   const [, LHS, RHS] = inMatch
 
-  const createAliasExpression = (content: string, offset: number) => {
+  const createAliasExpression = (
+    content: string,
+    offset: number,
+    asParam = false
+  ) => {
     const start = loc.start.offset + offset
     const end = start + content.length
-    return createSimpleExpression(content, false, getLoc(start, end))
+    return createExp(
+      content,
+      false,
+      getLoc(start, end),
+      ConstantTypes.NOT_CONSTANT,
+      asParam ? ExpParseMode.Params : ExpParseMode.Normal
+    )
   }
 
   const result: ForParseResult = {
@@ -502,7 +539,7 @@ function parseForExpression(
     let keyOffset: number | undefined
     if (keyContent) {
       keyOffset = exp.indexOf(keyContent, trimmedOffset + valueContent.length)
-      result.key = createAliasExpression(keyContent, keyOffset)
+      result.key = createAliasExpression(keyContent, keyOffset, true)
     }
 
     if (iteratorMatch[2]) {
@@ -516,14 +553,15 @@ function parseForExpression(
             result.key
               ? keyOffset! + keyContent.length
               : trimmedOffset + valueContent.length
-          )
+          ),
+          true
         )
       }
     }
   }
 
   if (valueContent) {
-    result.value = createAliasExpression(valueContent, trimmedOffset)
+    result.value = createAliasExpression(valueContent, trimmedOffset, true)
   }
 
   return result
@@ -929,8 +967,58 @@ function dirToAttr(dir: DirectiveNode): AttributeNode {
   return attr
 }
 
-function emitError(code: ErrorCodes, index: number) {
-  currentOptions.onError(createCompilerError(code, getLoc(index, index)))
+enum ExpParseMode {
+  Normal,
+  Params,
+  Statements,
+  Skip
+}
+
+function createExp(
+  content: SimpleExpressionNode['content'],
+  isStatic: SimpleExpressionNode['isStatic'] = false,
+  loc: SourceLocation,
+  constType: ConstantTypes = ConstantTypes.NOT_CONSTANT,
+  parseMode = ExpParseMode.Normal
+) {
+  const exp = createSimpleExpression(content, isStatic, loc, constType)
+  if (
+    !__BROWSER__ &&
+    !isStatic &&
+    currentOptions.prefixIdentifiers &&
+    parseMode !== ExpParseMode.Skip &&
+    content.trim()
+  ) {
+    if (isSimpleIdentifier(content)) {
+      exp.ast = null // fast path
+      return exp
+    }
+    try {
+      const plugins = currentOptions.expressionPlugins
+      const options: BabelOptions = {
+        plugins: plugins ? [...plugins, 'typescript'] : ['typescript']
+      }
+      if (parseMode === ExpParseMode.Statements) {
+        // v-on with multi-inline-statements, pad 1 char
+        exp.ast = parse(` ${content} `, options).program
+      } else if (parseMode === ExpParseMode.Params) {
+        exp.ast = parseExpression(`(${content})=>{}`, options)
+      } else {
+        // normal exp, wrap with parens
+        exp.ast = parseExpression(`(${content})`, options)
+      }
+    } catch (e: any) {
+      exp.ast = false // indicate an error
+      emitError(ErrorCodes.X_INVALID_EXPRESSION, loc.start.offset, e.message)
+    }
+  }
+  return exp
+}
+
+function emitError(code: ErrorCodes, index: number, message?: string) {
+  currentOptions.onError(
+    createCompilerError(code, getLoc(index, index), undefined, message)
+  )
 }
 
 function reset() {