docs for hook merging

Author: yyx990803

docs/en/pipeline/activate.md

@@ -8,7 +8,7 @@ Called on an incoming component during the activation phase when it is created a
 
   Call `transition.next()` to resolve the hook. Note calling `transition.abort()` here will not take the app back to the previous route because the transition has already been validated.
 
-### Return Value
+### Expected Return Value
 
 - Optionally return a Promise.
   - `resolve` -> `transition.next()`

docs/en/pipeline/can-activate.md

@@ -8,14 +8,15 @@ Called on an incoming component during the validation phase.
 
   Call `transition.next()` to resolve the hook. Calling `transition.abort()` will invalidate and cancel the transition.
 
-### Return Value
+### Expected Return Value
 
 - Optionally return a Promise:
 
   - `resolve(true)` -> `transition.next()`
   - `resolve(false)` -> `transition.abort()`
   - `reject(reason)` -> `transition.abort(reason)`
 
+
 - Optionally return a Boolean:
 
   - `true` -> `transition.next()`

docs/en/pipeline/can-deactivate.md

@@ -8,14 +8,15 @@ Called on a leaving component during the validation phase.
 
   Call `transition.next()` to resolve the hook. Calling `transition.abort()` will invalidate and cancel the transition.
 
-### Return Value
+### Expected Return Value
 
 - Optionally return a Promise:
 
   - `resolve(true)` -> `transition.next()`
   - `resolve(false)` -> `transition.abort()`
   - `reject(reason)` -> `transition.abort(reason)`
 
+
 - Optionally return a Boolean:
 
   - `true` -> `transition.next()`

docs/en/pipeline/can-reuse.md

@@ -10,7 +10,7 @@ This route options can either be a plain Boolean value, or a function that synch
 
   You can only access `transition.to` and `transition.from` in a `canReuse` hook.
 
-### Return Value
+### Expected Return Value
 
 - Must return a Boolean. Falsy values are treated as `false`.
 

docs/en/pipeline/data.md

@@ -8,13 +8,14 @@ Called on an incoming component during the activation phase, after the `activate
 
   Calling `transition.next(data)` will set each property in `data` on the component. For example, with `{ a: 1, b: 2 }`, the router will call `component.$set('a', 1)` and `component.$set('b', 2)`.
 
-### Return Value
+### Expected Return Value
 
 - optionally return a Promise.
   - `resolve(data)` -> `transition.next(data)`
   - `reject(reason)` -> `transition.abort(reason)`
 
-- or, return an Object containing Promises. See [Promise sugar](#promise-sugar) below.
+
+- **OR:** return an Object containing Promises. See [Promise sugar](#promise-sugar) below.
 
 ### Details
 

docs/en/pipeline/deactivate.md

@@ -8,7 +8,7 @@ Called on a leaving component the activation phase when it is about to be deacti
 
   Call `transition.next()` to resolve the hook. Note calling `transition.abort()` here will not take the app back to the previous route because the transition has already been validated.
 
-### Return Value
+### Expected Return Value
 
 - Optionally return a Promise.
   - `resolve` -> `transition.next()`

docs/en/pipeline/hooks.md

@@ -127,4 +127,16 @@ route: {
 }
 ```
 
-Check out the [advanced example](https://github.com/vuejs/vue-router/tree/dev/example/advanced) in the vue-router repo.
+For a full example of transition hooks in action, check out the [advanced example](https://github.com/vuejs/vue-router/tree/dev/example/advanced) in the vue-router repo.
+
+### Hook Merging
+
+Similar to component lifecycle hooks, the following route lifecycle hooks:
+
+- `data`
+- `activate`
+- `deactivate`
+
+...are merged during class extension or mixins. For example, if your component defines a route `data` hook, and uses a mixin that also provides a route `data` hook, both hooks will get called (mixin hooks called first) and the resolved data from all hooks will be merged together.
+
+Note that validation hooks like `canActivate`, `canDeactivate` and `canReuse` are always overwritten by the newer value.