From e26448656c2a9ec26d672f0add4086a207ead357 Mon Sep 17 00:00:00 2001
From: Luke Bennett <lukeeeebennettplus@gmail.com>
Date: Wed, 14 Jun 2017 13:12:58 +0100
Subject: [PATCH] Add warnHandler to allow users to set a custom warn callback,
 similar to errorHandler

---
 src/core/config.js               |  6 ++++++
 src/core/util/debug.js           | 10 +++++----
 test/unit/features/debug.spec.js | 36 +++++++++++++++++++++++++++++++-
 types/test/vue-test.ts           |  6 ++++++
 types/vue.d.ts                   |  1 +
 5 files changed, 54 insertions(+), 5 deletions(-)

diff --git a/src/core/config.js b/src/core/config.js
index fc472c79ab4..95663de8a6a 100644
--- a/src/core/config.js
+++ b/src/core/config.js
@@ -16,6 +16,7 @@ export type Config = {
   performance: boolean;
   devtools: boolean;
   errorHandler: ?(err: Error, vm: Component, info: string) => void;
+  warnHandler: ?(msg: string, vm: Component, trace: string) => void;
   ignoredElements: Array<string>;
   keyCodes: { [key: string]: number | Array<number> };
 
@@ -62,6 +63,11 @@ export default ({
    */
   errorHandler: null,
 
+  /**
+   * Warn handler for watcher warns
+   */
+  warnHandler: null,
+
   /**
    * Ignore certain custom elements
    */
diff --git a/src/core/util/debug.js b/src/core/util/debug.js
index ad19e167e57..7799024240d 100644
--- a/src/core/util/debug.js
+++ b/src/core/util/debug.js
@@ -15,10 +15,12 @@ if (process.env.NODE_ENV !== 'production') {
     .replace(/[-_]/g, '')
 
   warn = (msg, vm) => {
-    if (hasConsole && (!config.silent)) {
-      console.error(`[Vue warn]: ${msg}` + (
-        vm ? generateComponentTrace(vm) : ''
-      ))
+    const trace = vm ? generateComponentTrace(vm) : ''
+
+    if (config.warnHandler) {
+      config.warnHandler.call(null, msg, vm, trace)
+    } else if (hasConsole && (!config.silent)) {
+      console.error(`[Vue warn]: ${msg}${trace}`)
     }
   }
 
diff --git a/test/unit/features/debug.spec.js b/test/unit/features/debug.spec.js
index 49d2abf55fc..5fb5b48270c 100644
--- a/test/unit/features/debug.spec.js
+++ b/test/unit/features/debug.spec.js
@@ -1,5 +1,5 @@
 import Vue from 'vue'
-import { formatComponentName } from 'core/util/debug'
+import { formatComponentName, warn } from 'core/util/debug'
 
 describe('Debug utilities', () => {
   it('properly format component names', () => {
@@ -80,4 +80,38 @@ found in
            <Root>`
     ).toHaveBeenWarned()
   })
+
+  describe('warn', () => {
+    const msg = 'message'
+    const vm = new Vue()
+
+    it('calls warnHandler if warnHandler is set', () => {
+      Vue.config.warnHandler = jasmine.createSpy()
+
+      warn(msg, vm)
+
+      expect(Vue.config.warnHandler).toHaveBeenCalledWith(msg, vm, jasmine.any(String))
+
+      Vue.config.warnHandler = null
+    })
+
+    it('calls console.error if silent is false', () => {
+      Vue.config.silent = false
+
+      warn(msg, vm)
+
+      expect(msg).toHaveBeenWarned()
+      expect(console.error).toHaveBeenCalled()
+    })
+
+    it('does not call console.error if silent is true', () => {
+      Vue.config.silent = true
+
+      warn(msg, vm)
+
+      expect(console.error).not.toHaveBeenCalled()
+
+      Vue.config.silent = false
+    })
+  })
 })
diff --git a/types/test/vue-test.ts b/types/test/vue-test.ts
index b1848d2792f..b16e58470e1 100644
--- a/types/test/vue-test.ts
+++ b/types/test/vue-test.ts
@@ -63,6 +63,12 @@ class Test extends Vue {
         vm.testMethods();
       }
     };
+    config.warnHandler = (msg, vm) => {
+      if (vm instanceof Test) {
+        vm.testProperties();
+        vm.testMethods();
+      }
+    };
     config.keyCodes = { esc: 27 };
   }
 
diff --git a/types/vue.d.ts b/types/vue.d.ts
index b3bd1cdfea0..2ca8122dcbb 100644
--- a/types/vue.d.ts
+++ b/types/vue.d.ts
@@ -75,6 +75,7 @@ export declare class Vue {
     productionTip: boolean;
     performance: boolean;
     errorHandler(err: Error, vm: Vue, info: string): void;
+    warnHandler(msg: string, vm: Vue, trace: string): void;
     ignoredElements: string[];
     keyCodes: { [key: string]: number };
   }