fix #9467, Custom validation message in custom prop validator

src/core/util/props.js

@@ -137,9 +137,18 @@ function assertProp (
   }
   const validator = prop.validator
   if (validator) {
-    if (!validator(value)) {
+    let result
+    try {
+      result = validator(value)
+    } catch (error) {
+      result = error
+    }
+
+    if (result !== true) {
+      const message = result instanceof Error ? result.message.replace(/{{\s*name\s*}}/g, name) : 'custom validator check failed for prop "' + name + '".'
+
       warn(
-        'Invalid prop: custom validator check failed for prop "' + name + '".',
+        'Invalid prop: ' + message ,
         vm
       )
     }

test/unit/features/options/props.spec.js

@@ -264,6 +264,18 @@ describe('Options props', () => {
       makeInstance(123, null, v => v === 234)
       expect('custom validator check failed').toHaveBeenWarned()
     })
+
+    it('custom validator + custom error', () => {
+      const validator = v => {
+        if (v !== 123) throw new Error(`the prop '{{name}}' should be 123.`)
+
+        return true
+      }
+      makeInstance(123, null, validator)
+      expect(console.error.calls.count()).toBe(0)
+      makeInstance(234, null, validator)
+      expect(`the prop 'test' should be 123.`).toHaveBeenWarned()
+    })
 
     it('type check + custom validator', () => {
       makeInstance(123, Number, v => v === 123)