Warn if coerce is not a function (#2929)

Author: simplesmiler

src/compiler/compile-props.js

@@ -236,7 +236,7 @@ function processPropValue (vm, prop, rawValue, fn) {
   if (value === undefined) {
     value = getPropDefaultValue(vm, prop)
   }
-  value = coerceProp(prop, value)
+  value = coerceProp(prop, value, vm)
   const coerced = value !== rawValue
   if (!assertProp(prop, value, vm)) {
     value = undefined
@@ -374,13 +374,20 @@ function assertProp (prop, value, vm) {
  * @return {*}
  */
 
-function coerceProp (prop, value) {
+function coerceProp (prop, value, vm) {
   var coerce = prop.options.coerce
   if (!coerce) {
     return value
   }
-  // coerce is a function
-  return coerce(value)
+  if (typeof coerce === 'function') {
+    return coerce(value)
+  } else {
+    process.env.NODE_ENV !== 'production' && warn(
+      'Invalid coerce for prop "' + prop.name + '": expected function, got ' + typeof coerce + '.',
+      vm
+    )
+    return value
+  }
 }
 
 /**

test/unit/specs/directives/internal/prop_spec.js

@@ -423,6 +423,12 @@ describe('prop', function () {
       expect(getWarnCount()).toBe(0)
     })
 
+    it('warn if coerce is not a function', function () {
+      var coerce = 1
+      makeInstance('123', String, null, coerce)
+      expect(getWarnCount()).toBe(1)
+    })
+
     it('multiple types + custom validator', function () {
       makeInstance(123, [String, Boolean, Number], null, String)
       expect(getWarnCount()).toBe(0)