feat(devtools): warn against old devtools version

See #1338

diff --git a/packages/router/src/devtools.ts b/packages/router/src/devtools.ts
index a7d4f4e143e2e4b2d1182841bb7d37abb40d2977..ea20cdca2a6b5ea1e0fd19fbfc49de45a4c83366 100644 (file)
--- a/packages/router/src/devtools.ts
+++ b/packages/router/src/devtools.ts
@@ -72,6 +72,12 @@ export function addDevtools(app: App, router: Router, matcher: RouterMatcher) {
       app,
     },
     api => {
+      if (typeof api.now !== 'function') {
+        console.warn(
+          '[Vue Router]: You seem to be using an outdated version of Vue Devtools. Are you still using the Beta release instead of the stable one? You can find the links at https://devtools.vuejs.org/guide/installation.html.'
+        )
+      }
+
       // display state added by the router
       api.on.inspectComponent((payload, ctx) => {
         if (payload.instanceData) {