feat(vapor): generate more efficient runtime code for specific interpolation patterns

packages/compiler-vapor/__tests__/transforms/__snapshots__/vFor.spec.ts.snap

@@ -47,6 +47,27 @@ export function render(_ctx) {
 }"
 `;
 
+exports[`compiler: v-for > key only binding pattern 1`] = `
+"import { child as _child, toDisplayString as _toDisplayString, setText as _setText, createFor as _createFor, template as _template } from 'vue';
+const t0 = _template("<tr> </tr>", true)
+
+export function render(_ctx) {
+  const n0 = _createFor(() => (_ctx.rows), (_for_item0) => {
+    const n2 = t0()
+    const x2 = _child(n2)
+    let _row, _row_id
+    {
+      _row = _for_item0.value
+      _row_id = _row.id
+
+    }
+    _setText(x2, _toDisplayString(_row_id + _row_id))
+    return n2
+  }, (row) => (row.id))
+  return n0
+}"
+`;
+
 exports[`compiler: v-for > multi effect 1`] = `
 "import { setProp as _setProp, renderEffect as _renderEffect, createFor as _createFor, template as _template } from 'vue';
 const t0 = _template("<div></div>", true)
@@ -115,6 +136,75 @@ export function render(_ctx) {
 }"
 `;
 
+exports[`compiler: v-for > selector pattern 1`] = `
+"import { child as _child, toDisplayString as _toDisplayString, setText as _setText, createFor as _createFor, template as _template } from 'vue';
+const t0 = _template("<tr> </tr>", true)
+
+export function render(_ctx) {
+  const n0 = _createFor(() => (_ctx.rows), (_for_item0) => {
+    const n2 = t0()
+    const x2 = _child(n2)
+    _selector0_0(() => {
+      _setText(x2, _toDisplayString(_ctx.selected === _for_item0.value.id ? 'danger' : ''))
+    })
+    return n2
+  }, (row) => (row.id))
+  const _selector0_0 = n0.useSelector(() => _ctx.selected)
+  return n0
+}"
+`;
+
+exports[`compiler: v-for > selector pattern 2`] = `
+"import { setClass as _setClass, createFor as _createFor, template as _template } from 'vue';
+const t0 = _template("<tr></tr>", true)
+
+export function render(_ctx) {
+  const n0 = _createFor(() => (_ctx.rows), (_for_item0) => {
+    const n2 = t0()
+    _selector0_0(() => {
+      _setClass(n2, _ctx.selected === _for_item0.value.id ? 'danger' : '')
+    })
+    return n2
+  }, (row) => (row.id))
+  const _selector0_0 = n0.useSelector(() => _ctx.selected)
+  return n0
+}"
+`;
+
+exports[`compiler: v-for > selector pattern 3`] = `
+"import { setClass as _setClass, renderEffect as _renderEffect, createFor as _createFor, template as _template } from 'vue';
+const t0 = _template("<tr></tr>", true)
+
+export function render(_ctx) {
+  const n0 = _createFor(() => (_ctx.rows), (_for_item0) => {
+    const n2 = t0()
+    _renderEffect(() => {
+      const _row = _for_item0.value
+      _setClass(n2, _row.label === _row.id ? 'danger' : '')
+    })
+    return n2
+  }, (row) => (row.id))
+  return n0
+}"
+`;
+
+exports[`compiler: v-for > selector pattern 4`] = `
+"import { setClass as _setClass, createFor as _createFor, template as _template } from 'vue';
+const t0 = _template("<tr></tr>", true)
+
+export function render(_ctx) {
+  const n0 = _createFor(() => (_ctx.rows), (_for_item0) => {
+    const n2 = t0()
+    _selector0_0(() => {
+      _setClass(n2, { danger: _for_item0.value.id === _ctx.selected })
+    })
+    return n2
+  }, (row) => (row.id))
+  const _selector0_0 = n0.useSelector(() => _ctx.selected)
+  return n0
+}"
+`;
+
 exports[`compiler: v-for > v-for aliases w/ complex expressions 1`] = `
 "import { getDefaultValue as _getDefaultValue, child as _child, toDisplayString as _toDisplayString, setText as _setText, renderEffect as _renderEffect, createFor as _createFor, template as _template } from 'vue';
 const t0 = _template("<div> </div>", true)

packages/compiler-vapor/__tests__/transforms/vFor.spec.ts

@@ -67,6 +67,73 @@ describe('compiler: v-for', () => {
     ).lengthOf(1)
   })
 
+  test('key only binding pattern', () => {
+    expect(
+      compileWithVFor(
+        `
+          <tr
+            v-for="row of rows"
+            :key="row.id"
+          >
+            {{ row.id + row.id }}
+          </tr>
+      `,
+      ).code,
+    ).matchSnapshot()
+  })
+
+  test('selector pattern', () => {
+    expect(
+      compileWithVFor(
+        `
+          <tr
+            v-for="row of rows"
+            :key="row.id"
+          >
+            {{ selected === row.id ? 'danger' : '' }}
+          </tr>
+      `,
+      ).code,
+    ).matchSnapshot()
+
+    expect(
+      compileWithVFor(
+        `
+          <tr
+            v-for="row of rows"
+            :key="row.id"
+            :class="selected === row.id ? 'danger' : ''"
+          ></tr>
+      `,
+      ).code,
+    ).matchSnapshot()
+
+    // Should not be optimized because row.label is not from parent scope
+    expect(
+      compileWithVFor(
+        `
+          <tr
+            v-for="row of rows"
+            :key="row.id"
+            :class="row.label === row.id ? 'danger' : ''"
+          ></tr>
+      `,
+      ).code,
+    ).matchSnapshot()
+
+    expect(
+      compileWithVFor(
+        `
+          <tr
+            v-for="row of rows"
+            :key="row.id"
+            :class="{ danger: row.id === selected }"
+          ></tr>
+      `,
+      ).code,
+    ).matchSnapshot()
+  })
+
   test('multi effect', () => {
     const { code } = compileWithVFor(
       `<div v-for="(item, index) of items" :item="item" :index="index" />`,

packages/compiler-vapor/src/generators/block.ts

@@ -19,14 +19,13 @@ export function genBlock(
   context: CodegenContext,
   args: CodeFragment[] = [],
   root?: boolean,
-  customReturns?: (returns: CodeFragment[]) => CodeFragment[],
 ): CodeFragment[] {
   return [
     '(',
     ...args,
     ') => {',
     INDENT_START,
-    ...genBlockContent(oper, context, root, customReturns),
+    ...genBlockContent(oper, context, root),
     INDENT_END,
     NEWLINE,
     '}',
@@ -37,7 +36,7 @@ export function genBlockContent(
   block: BlockIRNode,
   context: CodegenContext,
   root?: boolean,
-  customReturns?: (returns: CodeFragment[]) => CodeFragment[],
+  genEffectsExtraFrag?: () => CodeFragment[],
 ): CodeFragment[] {
   const [frag, push] = buildCodeFragment()
   const { dynamic, effect, operation, returns } = block
@@ -56,7 +55,7 @@ export function genBlockContent(
   }
 
   push(...genOperations(operation, context))
-  push(...genEffects(effect, context))
+  push(...genEffects(effect, context, genEffectsExtraFrag))
 
   push(NEWLINE, `return `)
 
@@ -65,7 +64,7 @@ export function genBlockContent(
     returnNodes.length > 1
       ? genMulti(DELIMITERS_ARRAY, ...returnNodes)
       : [returnNodes[0] || 'null']
-  push(...(customReturns ? customReturns(returnsCode) : returnsCode))
+  push(...returnsCode)
 
   resetBlock()
   return frag

packages/compiler-vapor/src/generators/expression.ts

@@ -230,6 +230,7 @@ function canPrefix(name: string) {
 type DeclarationResult = {
   ids: Record<string, string>
   frag: CodeFragment[]
+  varNames: string[]
 }
 type DeclarationValue = {
   name: string
@@ -243,6 +244,7 @@ type DeclarationValue = {
 export function processExpressions(
   context: CodegenContext,
   expressions: SimpleExpressionNode[],
+  shouldDeclare: boolean,
 ): DeclarationResult {
   // analyze variables
   const { seenVariable, variableToExpMap, expToVariableMap, seenIdentifier } =
@@ -266,7 +268,11 @@ export function processExpressions(
     varDeclarations,
   )
 
-  return genDeclarations([...varDeclarations, ...expDeclarations], context)
+  return genDeclarations(
+    [...varDeclarations, ...expDeclarations],
+    context,
+    shouldDeclare,
+  )
 }
 
 function analyzeExpressions(expressions: SimpleExpressionNode[]) {
@@ -507,31 +513,41 @@ function processRepeatedExpressions(
 function genDeclarations(
   declarations: DeclarationValue[],
   context: CodegenContext,
+  shouldDeclare: boolean,
 ): DeclarationResult {
   const [frag, push] = buildCodeFragment()
   const ids: Record<string, string> = Object.create(null)
+  const varNames = new Set<string>()
 
   // process identifiers first as expressions may rely on them
   declarations.forEach(({ name, isIdentifier, value }) => {
     if (isIdentifier) {
       const varName = (ids[name] = `_${name}`)
-      push(`const ${varName} = `, ...genExpression(value, context), NEWLINE)
+      varNames.add(varName)
+      if (shouldDeclare) {
+        push(`const `)
+      }
+      push(`${varName} = `, ...genExpression(value, context), NEWLINE)
     }
   })
 
   // process expressions
   declarations.forEach(({ name, isIdentifier, value }) => {
     if (!isIdentifier) {
       const varName = (ids[name] = `_${name}`)
+      varNames.add(varName)
+      if (shouldDeclare) {
+        push(`const `)
+      }
       push(
-        `const ${varName} = `,
+        `${varName} = `,
         ...context.withId(() => genExpression(value, context), ids),
         NEWLINE,
       )
     }
   })
 
-  return { ids, frag }
+  return { ids, frag, varNames: [...varNames] }
 }
 
 function escapeRegExp(string: string) {