refactor(compiler-core): make ast.helpers a Set (vuejs#6774)

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

@@ -41,7 +41,7 @@ function createRoot(options: Partial<RootNode> = {}): RootNode {
   return {
     type: NodeTypes.ROOT,
     children: [],
-    helpers: [],
+    helpers: new Set(),
     components: [],
     directives: [],
     imports: [],
@@ -57,7 +57,7 @@ function createRoot(options: Partial<RootNode> = {}): RootNode {
 describe('compiler: codegen', () => {
   test('module mode preamble', () => {
     const root = createRoot({
-      helpers: [CREATE_VNODE, RESOLVE_DIRECTIVE]
+      helpers: new Set([CREATE_VNODE, RESOLVE_DIRECTIVE])
     })
     const { code } = generate(root, { mode: 'module' })
     expect(code).toMatch(
@@ -68,7 +68,7 @@ describe('compiler: codegen', () => {
 
   test('module mode preamble w/ optimizeImports: true', () => {
     const root = createRoot({
-      helpers: [CREATE_VNODE, RESOLVE_DIRECTIVE]
+      helpers: new Set([CREATE_VNODE, RESOLVE_DIRECTIVE])
     })
     const { code } = generate(root, { mode: 'module', optimizeImports: true })
     expect(code).toMatch(
@@ -82,7 +82,7 @@ describe('compiler: codegen', () => {
 
   test('function mode preamble', () => {
     const root = createRoot({
-      helpers: [CREATE_VNODE, RESOLVE_DIRECTIVE]
+      helpers: new Set([CREATE_VNODE, RESOLVE_DIRECTIVE])
     })
     const { code } = generate(root, { mode: 'function' })
     expect(code).toMatch(`const _Vue = Vue`)
@@ -94,7 +94,7 @@ describe('compiler: codegen', () => {
 
   test('function mode preamble w/ prefixIdentifiers: true', () => {
     const root = createRoot({
-      helpers: [CREATE_VNODE, RESOLVE_DIRECTIVE]
+      helpers: new Set([CREATE_VNODE, RESOLVE_DIRECTIVE])
     })
     const { code } = generate(root, {
       mode: 'function',

packages/compiler-core/src/ast.ts

@@ -100,7 +100,7 @@ export type TemplateChildNode =
 export interface RootNode extends Node {
   type: NodeTypes.ROOT
   children: TemplateChildNode[]
-  helpers: symbol[]
+  helpers: Set<symbol>
   components: string[]
   directives: string[]
   hoists: (JSChildNode | null)[]
@@ -556,7 +556,7 @@ export function createRoot(
   return {
     type: NodeTypes.ROOT,
     children,
-    helpers: [],
+    helpers: new Set(),
     components: [],
     directives: [],
     hoists: [],

packages/compiler-core/src/codegen.ts

@@ -208,7 +208,8 @@ export function generate(
     ssr
   } = context
 
-  const hasHelpers = ast.helpers.length > 0
+  const helpers = Array.from(ast.helpers)
+  const hasHelpers = helpers.length > 0
   const useWithBlock = !prefixIdentifiers && mode !== 'module'
   const genScopeId = !__BROWSER__ && scopeId != null && mode === 'module'
   const isSetupInlined = !__BROWSER__ && !!options.inline
@@ -249,7 +250,7 @@ export function generate(
     // function mode const declarations should be inside with block
     // also they should be renamed to avoid collision with user properties
     if (hasHelpers) {
-      push(`const { ${ast.helpers.map(aliasHelper).join(', ')} } = _Vue`)
+      push(`const { ${helpers.map(aliasHelper).join(', ')} } = _Vue`)
       push(`\n`)
       newline()
     }
@@ -330,11 +331,10 @@ function genFunctionPreamble(ast: RootNode, context: CodegenContext) {
   // In prefix mode, we place the const declaration at top so it's done
   // only once; But if we not prefixing, we place the declaration inside the
   // with block so it doesn't incur the `in` check cost for every helper access.
-  if (ast.helpers.length > 0) {
+  const helpers = Array.from(ast.helpers)
+  if (helpers.length > 0) {
     if (!__BROWSER__ && prefixIdentifiers) {
-      push(
-        `const { ${ast.helpers.map(aliasHelper).join(', ')} } = ${VueBinding}\n`
-      )
+      push(`const { ${helpers.map(aliasHelper).join(', ')} } = ${VueBinding}\n`)
     } else {
       // "with" mode.
       // save Vue in a separate variable to avoid collision
@@ -350,7 +350,7 @@ function genFunctionPreamble(ast: RootNode, context: CodegenContext) {
           CREATE_TEXT,
           CREATE_STATIC
         ]
-          .filter(helper => ast.helpers.includes(helper))
+          .filter(helper => helpers.includes(helper))
           .map(aliasHelper)
           .join(', ')
         push(`const { ${staticHelpers} } = _Vue\n`)
@@ -386,30 +386,32 @@ function genModulePreamble(
   } = context
 
   if (genScopeId && ast.hoists.length) {
-    ast.helpers.push(PUSH_SCOPE_ID, POP_SCOPE_ID)
+    ast.helpers.add(PUSH_SCOPE_ID)
+    ast.helpers.add(POP_SCOPE_ID)
   }
 
   // generate import statements for helpers
-  if (ast.helpers.length) {
+  if (ast.helpers.size) {
+    const helpers = Array.from(ast.helpers)
     if (optimizeImports) {
       // when bundled with webpack with code-split, calling an import binding
       // as a function leads to it being wrapped with `Object(a.b)` or `(0,a.b)`,
       // incurring both payload size increase and potential perf overhead.
       // therefore we assign the imports to variables (which is a constant ~50b
       // cost per-component instead of scaling with template size)
       push(
-        `import { ${ast.helpers
+        `import { ${helpers
           .map(s => helperNameMap[s])
           .join(', ')} } from ${JSON.stringify(runtimeModuleName)}\n`
       )
       push(
-        `\n// Binding optimization for webpack code-split\nconst ${ast.helpers
+        `\n// Binding optimization for webpack code-split\nconst ${helpers
           .map(s => `_${helperNameMap[s]} = ${helperNameMap[s]}`)
           .join(', ')}\n`
       )
     } else {
       push(
-        `import { ${ast.helpers
+        `import { ${helpers
           .map(s => `${helperNameMap[s]} as _${helperNameMap[s]}`)
           .join(', ')} } from ${JSON.stringify(runtimeModuleName)}\n`
       )

packages/compiler-core/src/transform.ts

@@ -324,7 +324,7 @@ export function transform(root: RootNode, options: TransformOptions) {
     createRootCodegen(root, context)
   }
   // finalize meta information
-  root.helpers = [...context.helpers.keys()]
+  root.helpers = new Set([...context.helpers.keys()])
   root.components = [...context.components]
   root.directives = [...context.directives]
   root.imports = context.imports

packages/compiler-sfc/src/compileScript.ts

@@ -1561,7 +1561,7 @@ export function compileScript(
       // avoid duplicated unref import
       // as this may get injected by the render function preamble OR the
       // css vars codegen
-      if (ast && ast.helpers.includes(UNREF)) {
+      if (ast && ast.helpers.has(UNREF)) {
         helperImports.delete('unref')
       }
       returned = code

packages/compiler-ssr/__tests__/ssrInjectCssVars.spec.ts

@@ -127,10 +127,10 @@ describe('ssr: inject <style vars>', () => {
       }"
     `)
     expect(result.ast.helpers).toMatchInlineSnapshot(`
-      Array [
+      Set {
         Symbol(mergeProps),
         Symbol(unref),
-      ]
+      }
     `)
   })
 })

packages/compiler-ssr/src/ssrCodegenTransform.ts

@@ -49,7 +49,7 @@ export function ssrCodegenTransform(ast: RootNode, options: CompilerOptions) {
       createCompoundExpression([`const _cssVars = { style: `, varsExp, `}`])
     )
     Array.from(cssContext.helpers.keys()).forEach(helper => {
-      if (!ast.helpers.includes(helper)) ast.helpers.push(helper)
+      ast.helpers.add(helper)
     })
   }
 
@@ -61,10 +61,13 @@ export function ssrCodegenTransform(ast: RootNode, options: CompilerOptions) {
   // Finalize helpers.
   // We need to separate helpers imported from 'vue' vs. '@vue/server-renderer'
   ast.ssrHelpers = Array.from(
-    new Set([...ast.helpers.filter(h => h in ssrHelpers), ...context.helpers])
+    new Set([
+      ...Array.from(ast.helpers).filter(h => h in ssrHelpers),
+      ...context.helpers
+    ])
   )
 
-  ast.helpers = ast.helpers.filter(h => !(h in ssrHelpers))
+  ast.helpers = new Set(Array.from(ast.helpers).filter(h => !(h in ssrHelpers)))
 }
 
 export type SSRTransformContext = ReturnType<typeof createSSRTransformContext>