fix: i18n reference to root causes memory leak (#1044) (#1151)

Author: lzxb

src/mixin.js

@@ -42,6 +42,16 @@ export default {
           options.i18n.silentFallbackWarn = rootI18n.silentFallbackWarn
           options.i18n.pluralizationRules = rootI18n.pluralizationRules
           options.i18n.preserveDirectiveContent = rootI18n.preserveDirectiveContent
+          this.$root.$once('hook:beforeDestroy', () => {
+            options.i18n.root = null;
+            options.i18n.formatter = null;
+            options.i18n.fallbackLocale = null;
+            options.i18n.formatFallbackMessages = null;
+            options.i18n.silentTranslationWarn = null;
+            options.i18n.silentFallbackWarn = null;
+            options.i18n.pluralizationRules = null;
+            options.i18n.preserveDirectiveContent = null;
+          });
         }
 
         // init locale messages via custom blocks

test/unit/issues.test.js

@@ -1,6 +1,7 @@
 import messages from './fixture/index'
 import { parse } from '../../src/format'
 import VueI18n from '../../src'
+import { Vue } from '../../src/install'
 const compiler = require('vue-template-compiler')
 
 const delay = time => new Promise(resolve => setTimeout(resolve, time))
@@ -498,6 +499,42 @@ describe('issues', () => {
       }).then(done)
     })
   })
+  // 1044
+  describe('#1044', () => {
+    it('should be free memory', done => {
+      const i18n = {
+        messages: {
+          hello: 'hello world!'
+        }
+      }
+      const Test = {
+        i18n,
+      }
+      const vm = new Vue({
+        components: {
+          Test
+        },
+        i18n: {
+          locale: 'en',
+        },
+        render (h) {
+          return h('Test')
+        }
+      }).$mount()
+      vm.$destroy();
+
+      assert.strictEqual(i18n.root, null)
+      assert.strictEqual(i18n.formatter, null)
+      assert.strictEqual(i18n.fallbackLocale, null)
+      assert.strictEqual(i18n.formatFallbackMessages, null)
+      assert.strictEqual(i18n.silentTranslationWarn, null)
+      assert.strictEqual(i18n.silentFallbackWarn, null)
+      assert.strictEqual(i18n.pluralizationRules, null)
+      assert.strictEqual(i18n.preserveDirectiveContent, null)
+
+      done();
+    });
+  })
 
   describe('#78, #464', () => {
     it('should fallback to default pluralization', () => {