[IMP[ component/hooks: add onWillStart and onWillUpdateProps

src/hooks.ts

@@ -64,11 +64,28 @@ function makeLifecycleHook(method: string, reverse: boolean = false) {
   }
 }
 
+function makeAsyncHook(method: string) {
+  return function(cb) {
+    const component: Component<any, any> = Component._current;
+    if (component.__owl__[method]) {
+      const current = component.__owl__[method];
+      component.__owl__[method] = function(...args) {
+        return Promise.all[(current.call(component, ...args), cb.call(component, ...args))];
+      };
+    } else {
+      component.__owl__[method] = cb;
+    }
+  };
+}
+
 export const onMounted = makeLifecycleHook("mountedCB", true);
 export const onWillUnmount = makeLifecycleHook("willUnmountCB");
 export const onWillPatch = makeLifecycleHook("willPatchCB");
 export const onPatched = makeLifecycleHook("patchedCB", true);
 
+export const onWillStart = makeAsyncHook("willStartCB");
+export const onWillUpdateProps = makeAsyncHook("willUpdatePropsCB");
+
 // -----------------------------------------------------------------------------
 // useRef
 // -----------------------------------------------------------------------------
@@ -100,7 +117,6 @@ export function useRef(name: string): Ref {
 // useSubEnv
 // -----------------------------------------------------------------------------
 
-
 /**
  * This hook is a simple way to let components use a sub environment.  Note that
  * like for all hooks, it is important that this is only called in the
@@ -109,4 +125,4 @@ export function useRef(name: string): Ref {
 export function useSubEnv(nextEnv) {
   const component = Component._current;
   component.env = Object.assign(Object.create(component.env), nextEnv);
-}
+}