feat(compiler): add whitespace option, deprecate preserveWhitespace option

close #9208

Author: yyx990803

Diff for: flow/compiler.js

@@ -6,7 +6,8 @@ declare type CompilerOptions = {
   isUnaryTag?: (tag: string) => ?boolean; // check if a tag is unary for the platform
   canBeLeftOpenTag?: (tag: string) => ?boolean; // check if a tag can be left opened
   isReservedTag?: (tag: string) => ?boolean; // check if a tag is a native for the platform
-  preserveWhitespace?: boolean; // preserve whitespace between elements?
+  preserveWhitespace?: boolean; // preserve whitespace between elements? (Deprecated)
+  whitespace?: 'preserve' | 'condense'; // whitespace handling strategy
   optimize?: boolean; // optimize static content?
 
   // web specific

Diff for: packages/vue-template-compiler/README.md

@@ -33,12 +33,48 @@ Note the returned function code uses `with` and thus cannot be used in strict mo
 
 #### Options
 
-It's possible to hook into the compilation process to support custom template features. **However, beware that by injecting custom compile-time modules, your templates will not work with other build tools built on standard built-in modules, e.g `vue-loader` and `vueify`.**
+- `whitespace`
+  - Type: `string`
+  - Valid values: `'preserve' | 'condense'`
+  - Default: `'preserve'`
 
-The optional `options` object can contain the following:
+  The default value `'preserve'` handles whitespaces as follows:
+
+  - A whitespace-only text node between element tags is condensed into a single space.
+  - All other whitespaces are preserved as-is.
+
+  If set to `'condense'`:
+
+  - A whitespace-only text node between element tags is removed if it contains new lines. Otherwise, it is condensed into a single space.
+  - Consecutive whitespaces inside a non-whitespace-only text node is condensed into a single space.
+
+  Using condense mode will result in smaller compiled code size and slightly improved performance. However, it will produce minor visual layout differences compared to plain HTML in certain cases.
+
+  **This option does not affect the `<pre>` tag.**
+
+  Example:
+
+  ``` html
+  <!-- source -->
+  <div>
+    <span>
+      foo
+    </span>   <span>bar</span>
+  </div>
+
+  <!-- whitespace: 'preserve' -->
+  <div> <span>
+    foo
+    </span> <span>bar</span> </div>
+
+  <!-- whitespace: 'condense' -->
+  <div><span> foo </span> <span>bar</span></div>
+  ```
 
 - `modules`
 
+  It's possible to hook into the compilation process to support custom template features. **However, beware that by injecting custom compile-time modules, your templates will not work with other build tools built on standard built-in modules, e.g `vue-loader` and `vueify`.**
+
   An array of compiler modules. For details on compiler modules, refer to the `ModuleOptions` type in [flow declarations](https://github.com/vuejs/vue/blob/dev/flow/compiler.js#L38-L45) and the [built-in modules](https://github.com/vuejs/vue/tree/dev/src/platforms/web/compiler/modules).
 
 - `directives`
@@ -59,9 +95,11 @@ The optional `options` object can contain the following:
 
   Refer to the implementation of some [built-in compile-time directives](https://github.com/vuejs/vue/tree/dev/src/platforms/web/compiler/directives).
 
-- `preserveWhitespace`
+- `preserveWhitespace` **Deprecated since 2.6**
+  - Type: `boolean`
+  - Default: `true`
 
-  Defaults to `true`. This means the compiled render function preserves all whitespace characters between HTML tags. If set to `false`, whitespace between tags will be ignored. This can result in slightly better performance but may affect layout for inline elements.
+  By default, the compiled render function preserves all whitespace characters between HTML tags. If set to `false`, whitespace between tags will be ignored. This can result in slightly better performance but may affect layout for inline elements.
 
 ---
 

Diff for: packages/vue-template-compiler/types/index.d.ts

@@ -7,6 +7,7 @@ interface CompilerOptions {
   modules?: ModuleOptions[];
   directives?: Record<string, DirectiveFunction>;
   preserveWhitespace?: boolean;
+  whitespace?: 'preserve' | 'condense';
 }
 
 interface CompiledResult {

Diff for: packages/vue-template-compiler/types/test.ts

@@ -10,6 +10,7 @@ import {
 // check compile options
 const compiled = compile("<div>hi</div>", {
   preserveWhitespace: false,
+  whitespace: 'condense',
   modules: [
     {
       preTransformNode: el => el,

Diff for: src/compiler/parser/index.js

@@ -30,6 +30,9 @@ const argRE = /:(.*)$/
 export const bindRE = /^:|^v-bind:/
 const modifierRE = /\.[^.]+/g
 
+const lineBreakRE = /[\r\n]/
+const whitespaceRE = /\s+/g
+
 const decodeHTMLCached = cached(he.decode)
 
 // configurable state
@@ -79,6 +82,7 @@ export function parse (
 
   const stack = []
   const preserveWhitespace = options.preserveWhitespace !== false
+  const whitespaceOption = options.whitespace
   let root
   let currentParent
   let inVPre = false
@@ -235,11 +239,13 @@ export function parse (
     },
 
     end (tag, start, end) {
-      // remove trailing whitespace
       const element = stack[stack.length - 1]
-      const lastNode = element.children[element.children.length - 1]
-      if (lastNode && lastNode.type === 3 && lastNode.text === ' ' && !inPre) {
-        element.children.pop()
+      if (!inPre) {
+        // remove trailing whitespace node
+        const lastNode = element.children[element.children.length - 1]
+        if (lastNode && lastNode.type === 3 && lastNode.text === ' ') {
+          element.children.pop()
+        }
       }
       // pop stack
       stack.length -= 1
@@ -276,11 +282,27 @@ export function parse (
         return
       }
       const children = currentParent.children
-      text = inPre || text.trim()
-        ? isTextTag(currentParent) ? text : decodeHTMLCached(text)
-        // only preserve whitespace if its not right after a starting tag
-        : preserveWhitespace && children.length ? ' ' : ''
+      if (inPre || text.trim()) {
+        text = isTextTag(currentParent) ? text : decodeHTMLCached(text)
+      } else if (!children.length) {
+        // remove the whitespace-only node right after an opening tag
+        text = ''
+      } else if (whitespaceOption) {
+        if (whitespaceOption === 'condense') {
+          // in condense mode, remove the whitespace node if it contains
+          // line break, otherwise condense to a single space
+          text = lineBreakRE.test(text) ? '' : ' '
+        } else {
+          text = ' '
+        }
+      } else {
+        text = preserveWhitespace ? ' ' : ''
+      }
       if (text) {
+        if (whitespaceOption === 'condense') {
+          // condense consecutive whitespaces into single space
+          text = text.replace(whitespaceRE, ' ')
+        }
         let res
         let child: ?ASTNode
         if (!inVPre && text !== ' ' && (res = parseText(text, delimiters))) {

Diff for: test/unit/modules/compiler/parser.spec.js

@@ -757,4 +757,45 @@ describe('parser', () => {
     const ast = parse(`<p>{{\r\nmsg\r\n}}</p>`, baseOptions)
     expect(ast.children[0].expression).toBe('_s(msg)')
   })
+
+  it('preserveWhitespace: false', () => {
+    const options = extend({
+      preserveWhitespace: false
+    }, baseOptions)
+
+     const ast = parse('<p>\n  Welcome to <b>Vue.js</b>    <i>world</i>  \n  <span>.\n  Have fun!\n</span></p>', options)
+    expect(ast.tag).toBe('p')
+    expect(ast.children.length).toBe(4)
+    expect(ast.children[0].type).toBe(3)
+    expect(ast.children[0].text).toBe('\n  Welcome to ')
+    expect(ast.children[1].tag).toBe('b')
+    expect(ast.children[1].children[0].text).toBe('Vue.js')
+    expect(ast.children[2].tag).toBe('i')
+    expect(ast.children[2].children[0].text).toBe('world')
+    expect(ast.children[3].tag).toBe('span')
+    expect(ast.children[3].children[0].text).toBe('.\n  Have fun!\n')
+  })
+
+  it(`whitespace: 'condense'`, () => {
+    const options = extend({
+      whitespace: 'condense',
+      // should be ignored when whitespace is specified
+      preserveWhitespace: false
+    }, baseOptions)
+    const ast = parse('<p>\n  Welcome to <b>Vue.js</b>    <i>world</i>  \n  <span>.\n  Have fun!\n</span></p>', options)
+    expect(ast.tag).toBe('p')
+    expect(ast.children.length).toBe(5)
+    expect(ast.children[0].type).toBe(3)
+    expect(ast.children[0].text).toBe(' Welcome to ')
+    expect(ast.children[1].tag).toBe('b')
+    expect(ast.children[1].children[0].text).toBe('Vue.js')
+    expect(ast.children[2].type).toBe(3)
+    // should condense inline whitespace into single space
+    expect(ast.children[2].text).toBe(' ')
+    expect(ast.children[3].tag).toBe('i')
+    expect(ast.children[3].children[0].text).toBe('world')
+    // should have removed the whitespace node between tags that contains newlines
+    expect(ast.children[4].tag).toBe('span')
+    expect(ast.children[4].children[0].text).toBe('. Have fun! ')
+  })
 })