fix: don't generate <title> tag if metaInfo.title is null or false (#409)

Author: lmichelin

src/server/generators/title.js

@@ -8,6 +8,9 @@
 export default function titleGenerator (appId, { attribute } = {}, type, data) {
   return {
     text () {
+      if (!data) {
+        return ''
+      }
       return `<${type}>${data}</${type}>`
     }
   }

src/shared/escaping.js

@@ -1,4 +1,4 @@
-import { isString, isArray, isObject } from '../utils/is-type'
+import { isString, isArray, isPureObject } from '../utils/is-type'
 import { includes } from '../utils/array'
 import { metaInfoOptionKeys, disableOptionKeys } from './constants'
 
@@ -55,11 +55,11 @@ export function escape (info, options, escapeOptions) {
       escaped[key] = doEscape(value)
     } else if (isArray(value)) {
       escaped[key] = value.map((v) => {
-        return isObject(v)
+        return isPureObject(v)
           ? escape(v, options, escapeOptions)
           : doEscape(v)
       })
-    } else if (isObject(value)) {
+    } else if (isPureObject(value)) {
       escaped[key] = escape(value, options, escapeOptions)
     } else {
       escaped[key] = value

src/utils/is-type.js

@@ -15,6 +15,10 @@ export function isObject (arg) {
   return typeof arg === 'object'
 }
 
+export function isPureObject (arg) {
+  return typeof arg === 'object' && arg !== null
+}
+
 export function isFunction (arg) {
   return typeof arg === 'function'
 }

test/unit/escaping.test.js

@@ -39,6 +39,31 @@ describe('escaping', () => {
     })
   })
 
+  test('null title is left as it is', () => {
+    const component = new Vue({
+      metaInfo: {
+        title: null
+      }
+    })
+
+    expect(getMetaInfo(component, [[/&/g, '&']])).toEqual({
+      title: null,
+      titleChunk: '',
+      titleTemplate: '%s',
+      htmlAttrs: {},
+      headAttrs: {},
+      bodyAttrs: {},
+      meta: [],
+      base: [],
+      link: [],
+      style: [],
+      script: [],
+      noscript: [],
+      __dangerouslyDisableSanitizers: [],
+      __dangerouslyDisableSanitizersByTagID: {}
+    })
+  })
+
   test('special chars are escaped unless disabled by vmid', () => {
     const component = new Vue({
       metaInfo: {

test/unit/generators.test.js

@@ -1,6 +1,7 @@
 import _generateServerInjector from '../../src/server/generateServerInjector'
 import { defaultOptions } from '../../src/shared/constants'
 import metaInfoData from '../utils/meta-info-data'
+import { titleGenerator } from '../../src/server/generators'
 
 const generateServerInjector = (type, data) => _generateServerInjector('test', defaultOptions, type, data)
 
@@ -59,3 +60,10 @@ describe('generators', () => {
     })
   })
 })
+
+describe('title generator should return an empty string when title is null', () => {
+  const title = null
+  const generatedTitle = titleGenerator(0, {}, 'title', title)
+
+  expect(generatedTitle.text()).toEqual('')
+})