wip(compiler-ssr): v-if

packages/compiler-ssr/src/ssrCodegenTransform.ts

@@ -1,7 +1,6 @@
 import {
   RootNode,
   BlockStatement,
-  CallExpression,
   TemplateLiteral,
   createCallExpression,
   createTemplateLiteral,
@@ -10,10 +9,13 @@ import {
   ElementTypes,
   createBlockStatement,
   CompilerOptions,
-  isText
+  isText,
+  IfStatement,
+  CallExpression
 } from '@vue/compiler-dom'
 import { isString, escapeHtml, NO } from '@vue/shared'
 import { INTERPOLATE } from './runtimeHelpers'
+import { processIf } from './transforms/ssrVIf'
 
 // Because SSR codegen output is completely different from client-side output
 // (e.g. multiple elements can be concatenated into a single template literal
@@ -37,22 +39,19 @@ export function ssrCodegenTransform(ast: RootNode, options: CompilerOptions) {
   ast.codegenNode = createBlockStatement(context.body)
 }
 
-type SSRTransformContext = ReturnType<typeof createSSRTransformContext>
+export type SSRTransformContext = ReturnType<typeof createSSRTransformContext>
 
-function createSSRTransformContext(options: CompilerOptions) {
+export function createSSRTransformContext(options: CompilerOptions) {
   const body: BlockStatement['body'] = []
-  let currentCall: CallExpression | null = null
   let currentString: TemplateLiteral | null = null
 
   return {
     options,
     body,
     pushStringPart(part: TemplateLiteral['elements'][0]) {
-      if (!currentCall) {
-        currentCall = createCallExpression(`_push`)
-        body.push(currentCall)
-      }
       if (!currentString) {
+        const currentCall = createCallExpression(`_push`)
+        body.push(currentCall)
         currentString = createTemplateLiteral([])
         currentCall.arguments.push(currentString)
       }
@@ -63,11 +62,16 @@ function createSSRTransformContext(options: CompilerOptions) {
       } else {
         bufferedElements.push(part)
       }
+    },
+    pushStatement(statement: IfStatement | CallExpression) {
+      // close current string
+      currentString = null
+      body.push(statement)
     }
   }
 }
 
-function processChildren(
+export function processChildren(
   children: TemplateChildNode[],
   context: SSRTransformContext
 ) {
@@ -98,7 +102,7 @@ function processChildren(
     } else if (child.type === NodeTypes.INTERPOLATION) {
       context.pushStringPart(createCallExpression(INTERPOLATE, [child.content]))
     } else if (child.type === NodeTypes.IF) {
-      // TODO
+      processIf(child, context)
     } else if (child.type === NodeTypes.FOR) {
       // TODO
     }

packages/compiler-ssr/src/transforms/ssrTransformElement.ts

@@ -8,33 +8,6 @@ import {
 } from '@vue/compiler-dom'
 import { escapeHtml } from '@vue/shared'
 
-/*
-## Simple Element
-
-``` html
-<div></div>
-```
-``` js
-return function render(_ctx, _push, _parent) {
-  _push(`<div></div>`)
-}
-```
-
-## Consecutive Elements
-
-``` html
-<div>
-  <span></span>
-</div>
-<div></div>
-```
-``` js
-return function render(_ctx, _push, _parent) {
-  _push(`<div><span></span></div><div></div>`)
-}
-```
-*/
-
 export const ssrTransformElement: NodeTransform = (node, context) => {
   if (
     node.type === NodeTypes.ELEMENT &&

packages/compiler-ssr/src/transforms/ssrVIf.ts

@@ -1,3 +1,76 @@
-import { NodeTransform } from '@vue/compiler-dom'
+import {
+  createStructuralDirectiveTransform,
+  processIfBranches,
+  IfNode,
+  createIfStatement,
+  createBlockStatement,
+  createCallExpression,
+  IfBranchNode,
+  BlockStatement,
+  NodeTypes
+} from '@vue/compiler-dom'
+import {
+  SSRTransformContext,
+  createSSRTransformContext,
+  processChildren
+} from '../ssrCodegenTransform'
 
-export const ssrTransformIf: NodeTransform = () => {}
+// This is the plugin for the first transform pass, which simply constructs the
+// if node and its branches.
+export const ssrTransformIf = createStructuralDirectiveTransform(
+  /^(if|else|else-if)$/,
+  processIfBranches
+)
+
+// This is called during the 2nd transform pass to construct the SSR-sepcific
+// codegen nodes.
+export function processIf(node: IfNode, context: SSRTransformContext) {
+  const [rootBranch] = node.branches
+  const ifStatement = createIfStatement(
+    rootBranch.condition!,
+    processIfBranch(rootBranch, context)
+  )
+  context.pushStatement(ifStatement)
+
+  let currentIf = ifStatement
+  for (let i = 1; i < node.branches.length; i++) {
+    const branch = node.branches[i]
+    const branchBlockStatement = processIfBranch(branch, context)
+    if (branch.condition) {
+      // else-if
+      currentIf = currentIf.alternate = createIfStatement(
+        branch.condition,
+        branchBlockStatement
+      )
+    } else {
+      // else
+      currentIf.alternate = branchBlockStatement
+    }
+  }
+
+  if (!currentIf.alternate) {
+    currentIf.alternate = createBlockStatement([
+      createCallExpression(`_push`, ['`<!---->`'])
+    ])
+  }
+}
+
+function processIfBranch(
+  branch: IfBranchNode,
+  context: SSRTransformContext
+): BlockStatement {
+  const { children } = branch
+  const firstChild = children[0]
+  // TODO optimize away nested fragments when the only child is a ForNode
+  const needFragmentWrapper =
+    children.length !== 1 || firstChild.type !== NodeTypes.ELEMENT
+  const childContext = createSSRTransformContext(context.options)
+  if (needFragmentWrapper) {
+    childContext.pushStringPart(`<!---->`)
+  }
+  processChildren(branch.children, childContext)
+  if (needFragmentWrapper) {
+    childContext.pushStringPart(`<!---->`)
+  }
+  return createBlockStatement(childContext.body)
+}