Fetch lesson sizes before commiting new lessons

so that they can be commited together with their sizes.

Fixes learningequality#10797

kolibri/plugins/coach/assets/src/modules/lessonsRoot/actions.js

@@ -16,24 +16,37 @@ export function refreshClassLessons(store, classId) {
     force: true,
   })
     .then(lessons => {
+      // Fetch lesson sizes before commiting new lessons
+      // so that they can be commited together with their sizes.
+      // Fixes https://github.com/learningequality/kolibri/issues/10797
+      if (Object.keys(lessons).length > 0) {
+        return store.dispatch('fetchLessonsSizes', classId, false).then(sizes => {
+          return { lessons, sizes };
+        });
+      } else {
+        return { lessons, sizes: null };
+      }
+    })
+    .then(({ lessons, sizes }) => {
       store.commit('SET_CLASS_LESSONS', lessons);
+      if (sizes) {
+        store.commit('SET_CLASS_LESSONS_SIZES', sizes);
+      }
       // resolve lessons in case it's needed
       return lessons;
     })
-    .then(lessons => {
-      if (Object.keys(lessons).length > 0) {
-        return store.dispatch('fetchLessonsSizes', classId);
-      }
-    })
     .catch(error => {
       return store.dispatch('handleApiError', { error }, { root: true });
     });
 }
 
-export function fetchLessonsSizes(store, classId) {
+export function fetchLessonsSizes(store, classId, shouldCommit = true) {
   return LessonResource.fetchLessonsSizes({ collection: classId })
     .then(sizes => {
-      store.commit('SET_CLASS_LESSONS_SIZES', sizes);
+      if (shouldCommit) {
+        store.commit('SET_CLASS_LESSONS_SIZES', sizes);
+      }
+      return sizes;
     })
     .catch(error => {
       return store.dispatch('handleApiError', { error }, { root: true });