Throw error when component is undefined or null (#2038)

src/create-route-map.js

@@ -47,7 +47,8 @@ function addRouteRecord (
   nameMap: Dictionary<RouteRecord>,
   route: RouteConfig,
   parent?: RouteRecord,
-  matchAs?: string
+  matchAs?: string,
+  isAnAlias?: boolean
 ) {
   const { path, name } = route
   if (process.env.NODE_ENV !== 'production') {
@@ -57,6 +58,12 @@ function addRouteRecord (
       `route config "component" for path: ${String(path || name)} cannot be a ` +
       `string id. Use an actual component instead.`
     )
+    warn(
+      route.component || route.components || route.redirect || route.beforeEnter || isAnAlias,
+      `route config "component" for path: ${String(path || name)} should be either a ` +
+      `component (or named component), redirection, navigation guard, or an alias ` +
+      `to another root.`
+    )
   }
 
   const pathToRegexpOptions: PathToRegexpOptions = route.pathToRegexpOptions || {}
@@ -128,7 +135,8 @@ function addRouteRecord (
         nameMap,
         aliasRoute,
         parent,
-        record.path || '/' // matchAs
+        record.path || '/', // matchAs
+        true
       )
     })
   }

test/unit/specs/create-map.spec.js

@@ -78,6 +78,12 @@ describe('Creating Route Map', function () {
     }).toThrowError(/"path" is required/)
   })
 
+  it('in development, throws if component is null or undefined', function () {
+    process.env.NODE_ENV = 'development'
+    maps = createRouteMap([{ path: '/' }])
+    expect(console.warn).toHaveBeenCalled()
+  })
+
   it('in production, it has not logged this warning', function () {
     maps = createRouteMap(routes)
     expect(console.warn).not.toHaveBeenCalled()