feat(compiler): transformStyle + context.hoist

packages/compiler-core/src/ast.ts

@@ -68,6 +68,7 @@ export interface RootNode extends Node {
   children: ChildNode[]
   imports: string[]
   statements: string[]
+  hoists: JSChildNode[]
 }
 
 export interface ElementNode extends Node {

packages/compiler-core/src/codegen.ts

@@ -148,14 +148,16 @@ export function generate(
   if (mode === 'function') {
     // generate const declarations for helpers
     if (imports) {
-      push(`const { ${imports} } = Vue\n\n`)
+      push(`const { ${imports} } = Vue\n`)
     }
+    genHoists(ast.hoists, context)
     push(`return `)
   } else {
     // generate import statements for helpers
     if (imports) {
-      push(`import { ${imports} } from 'vue'\n\n`)
+      push(`import { ${imports} } from 'vue'\n`)
     }
+    genHoists(ast.hoists, context)
     push(`export default `)
   }
   push(`function render() {`)
@@ -190,6 +192,15 @@ export function generate(
   }
 }
 
+function genHoists(hoists: JSChildNode[], context: CodegenContext) {
+  hoists.forEach((exp, i) => {
+    context.push(`const _hoisted_${i + 1} = `)
+    genNode(exp, context)
+    context.newline()
+  })
+  context.newline()
+}
+
 // This will generate a single vnode call if:
 // - The list has length === 1, AND:
 // - This is a root node, OR:

packages/compiler-core/src/index.ts

@@ -10,6 +10,7 @@ import { transformOn } from './transforms/vOn'
 import { transformBind } from './transforms/vBind'
 import { transformExpression } from './transforms/transformExpression'
 import { defaultOnError, createCompilerError, ErrorCodes } from './errors'
+import { transformStyle } from './transforms/transformStyle'
 
 export type CompilerOptions = ParserOptions & TransformOptions & CodegenOptions
 
@@ -33,6 +34,7 @@ export function compile(
       transformIf,
       transformFor,
       ...(prefixIdentifiers ? [transformExpression] : []),
+      transformStyle,
       transformElement,
       ...(options.nodeTransforms || []) // user transforms
     ],
@@ -53,7 +55,7 @@ export {
   createStructuralDirectiveTransform,
   TransformOptions,
   TransformContext,
-  NodeTransform as Transform,
+  NodeTransform,
   StructuralDirectiveTransform
 } from './transform'
 export {
@@ -64,8 +66,3 @@ export {
 } from './codegen'
 export { ErrorCodes, CompilerError, createCompilerError } from './errors'
 export * from './ast'
-
-// debug
-export {
-  transformElement as prepareElementForCodegen
-} from './transforms/transformElement'

packages/compiler-core/src/parse.ts

@@ -84,6 +84,7 @@ export function parse(content: string, options: ParserOptions = {}): RootNode {
     children: parseChildren(context, TextModes.DATA, []),
     imports: [],
     statements: [],
+    hoists: [],
     loc: getSelection(context, start)
   }
 }

packages/compiler-core/src/transform.ts

@@ -6,7 +6,9 @@ import {
   ElementNode,
   DirectiveNode,
   Property,
-  ExpressionNode
+  ExpressionNode,
+  createExpression,
+  JSChildNode
 } from './ast'
 import { isString, isArray } from '@vue/shared'
 import { CompilerError, defaultOnError } from './errors'
@@ -52,6 +54,7 @@ export interface TransformContext extends Required<TransformOptions> {
   root: RootNode
   imports: Set<string>
   statements: string[]
+  hoists: JSChildNode[]
   identifiers: { [name: string]: number | undefined }
   parent: ParentNode
   childIndex: number
@@ -61,6 +64,7 @@ export interface TransformContext extends Required<TransformOptions> {
   onNodeRemoved: () => void
   addIdentifier(exp: ExpressionNode): void
   removeIdentifier(exp: ExpressionNode): void
+  hoist(exp: JSChildNode): ExpressionNode
 }
 
 function createTransformContext(
@@ -76,6 +80,7 @@ function createTransformContext(
     root,
     imports: new Set(),
     statements: [],
+    hoists: [],
     identifiers: {},
     prefixIdentifiers,
     nodeTransforms,
@@ -125,6 +130,14 @@ function createTransformContext(
     },
     removeIdentifier({ content }) {
       ;(context.identifiers[content] as number)--
+    },
+    hoist(exp) {
+      context.hoists.push(exp)
+      return createExpression(
+        `_hoisted_${context.hoists.length}`,
+        false,
+        exp.loc
+      )
     }
   }
   return context
@@ -135,6 +148,7 @@ export function transform(root: RootNode, options: TransformOptions) {
   traverseChildren(root, context)
   root.imports = [...context.imports]
   root.statements = context.statements
+  root.hoists = context.hoists
 }
 
 export function traverseChildren(

packages/compiler-core/src/transforms/transformElement.ts

@@ -108,6 +108,7 @@ function buildProps(
   props: PropsExpression
   directives: DirectiveNode[]
 } {
+  let isStatic = true
   let properties: ObjectExpression['properties'] = []
   const mergeArgs: PropsExpression[] = []
   const runtimeDirectives: DirectiveNode[] = []
@@ -130,6 +131,7 @@ function buildProps(
       )
     } else {
       // directives
+      isStatic = false
       const { name, arg, exp, loc } = prop
       // special case for v-bind and v-on with no argument
       const isBind = name === 'bind'
@@ -208,6 +210,11 @@ function buildProps(
     )
   }
 
+  // hoist the object if it's fully static
+  if (isStatic) {
+    propsExpression = context.hoist(propsExpression)
+  }
+
   return {
     props: propsExpression,
     directives: runtimeDirectives
@@ -233,10 +240,8 @@ function dedupeProperties(properties: Property[]): Property[] {
     const name = prop.key.content
     const existing = knownProps[name]
     if (existing) {
-      if (name.startsWith('on')) {
+      if (name.startsWith('on') || name === 'style') {
         mergeAsArray(existing, prop)
-      } else if (name === 'style') {
-        mergeStyles(existing, prop)
       } else if (name === 'class') {
         mergeClasses(existing, prop)
       }
@@ -260,25 +265,9 @@ function mergeAsArray(existing: Property, incoming: Property) {
   }
 }
 
-// Merge dynamic and static style into a single prop
-export function mergeStyles(existing: Property, incoming: Property) {
-  if (
-    existing.value.type === NodeTypes.JS_OBJECT_EXPRESSION &&
-    incoming.value.type === NodeTypes.JS_OBJECT_EXPRESSION
-  ) {
-    // if both are objects, merge the object expressions.
-    // style="color: red" :style="{ a: b }"
-    // -> { color: "red", a: b }
-    existing.value.properties.push(...incoming.value.properties)
-  } else {
-    // otherwise merge as array
-    // style="color:red" :style="a"
-    // -> style: [{ color: "red" }, a]
-    mergeAsArray(existing, incoming)
-  }
-}
-
 // Merge dynamic and static class into a single prop
+// :class="expression" class="string"
+// -> class: expression + "string"
 function mergeClasses(existing: Property, incoming: Property) {
   const e = existing.value as ExpressionNode
   const children =
@@ -289,8 +278,6 @@ function mergeClasses(existing: Property, incoming: Property) {
         children: undefined
       }
     ])
-  // :class="expression" class="string"
-  // -> class: expression + "string"
   children.push(` + " " + `, incoming.value as ExpressionNode)
 }
 

packages/compiler-core/src/transforms/transformExpression.ts

@@ -28,12 +28,11 @@ export const transformExpression: NodeTransform = (node, context) => {
         if (prop.arg && !prop.arg.isStatic) {
           if (prop.name === 'class') {
             // TODO special expression optimization for classes
+            processExpression(prop.arg, context)
           } else {
             processExpression(prop.arg, context)
           }
         }
-      } else if (prop.name === 'style') {
-        // TODO parse inline CSS literals into objects
       }
     }
   }

packages/compiler-core/src/transforms/transformStyle.ts

@@ -0,0 +1,37 @@
+import { NodeTransform } from '../transform'
+import { NodeTypes, createExpression } from '../ast'
+
+// prase inline CSS strings for static style attributes into an object
+export const transformStyle: NodeTransform = (node, context) => {
+  if (node.type === NodeTypes.ELEMENT) {
+    node.props.forEach((p, i) => {
+      if (p.type === NodeTypes.ATTRIBUTE && p.name === 'style' && p.value) {
+        // replace p with an expression node
+        const parsed = JSON.stringify(parseInlineCSS(p.value.content))
+        const exp = context.hoist(createExpression(parsed, false, p.loc))
+        node.props[i] = {
+          type: NodeTypes.DIRECTIVE,
+          name: `bind`,
+          arg: createExpression(`style`, true, p.loc),
+          exp,
+          modifiers: [],
+          loc: p.loc
+        }
+      }
+    })
+  }
+}
+
+const listDelimiterRE = /;(?![^(]*\))/g
+const propertyDelimiterRE = /:(.+)/
+
+function parseInlineCSS(cssText: string): Record<string, string> {
+  const res: Record<string, string> = {}
+  cssText.split(listDelimiterRE).forEach(function(item) {
+    if (item) {
+      const tmp = item.split(propertyDelimiterRE)
+      tmp.length > 1 && (res[tmp[0].trim()] = tmp[1].trim())
+    }
+  })
+  return res
+}