fix v-model number conversion (fix #3140)

flow/component.js

@@ -94,6 +94,8 @@ declare interface Component {
   ) => Object | void;
   // toString
   _s: (value: any) => string;
+  // toNumber
+  _n: (value: string) => number | string;
   // resolveFilter
   _f: (id: string) => Function;
   // renderList

src/core/instance/render.js

@@ -5,7 +5,7 @@ import VNode, { emptyVNode } from '../vdom/vnode'
 import { normalizeChildren } from '../vdom/helpers'
 import {
   warn, bind, isObject, toObject,
-  nextTick, resolveAsset, renderString
+  nextTick, resolveAsset, renderString, toNumber
 } from '../util/index'
 
 import {
@@ -96,6 +96,8 @@ export function renderMixin (Vue: Class<Component>) {
 
   // toString for mustaches
   Vue.prototype._s = renderString
+  // number conversion
+  Vue.prototype._n = toNumber
 
   // filter resolution helper
   const identity = _ => _

src/platforms/web/compiler/directives/model.js

@@ -101,7 +101,7 @@ function genDefaultModel (
 
   const valueExpression = `$event.target.value${trim ? '.trim()' : ''}`
   let code = number || type === 'number'
-    ? `${value}=Number(${valueExpression})`
+    ? `${value}=_n(${valueExpression})`
     : `${value}=${valueExpression}`
   if (needCompositionGuard) {
     code = `if($event.target.composing)return;${code}`

src/shared/util.js

@@ -11,6 +11,15 @@ export function renderString (val: any): string {
       : String(val)
 }
 
+/**
+ * Convert a input value to a number for persistence.
+ * If the conversion fails, return original string.
+ */
+export function toNumber (val: string): number | string {
+  const n = parseFloat(val, 10)
+  return (n || n === 0) ? n : val
+}
+
 /**
  * Make a map and return a function for checking if a key
  * is in that map.

test/unit/features/directives/model-text.spec.js

@@ -45,7 +45,10 @@ describe('Directive v-model text', () => {
     expect(vm.test).toBe(1)
     vm.$el.value = '2'
     triggerEvent(vm.$el, 'input')
-    expect(vm.test).toBe(2)
+    // should let strings pass through
+    vm.$el.value = 'f'
+    triggerEvent(vm.$el, 'input')
+    expect(vm.test).toBe('f')
   })
 
   it('.trim modifier', () => {