melib/backends: MailBackend::refresh() returns Result

Handle cases were refresh() would fail properly. Fixes a crash reported in #13

melib/src/backends.rs

@@ -252,8 +252,8 @@ pub trait MailBackend: ::std::fmt::Debug + Send + Sync {
         &mut self,
         folder_hash: FolderHash,
         sender: RefreshEventConsumer,
-    ) -> Async<Result<Vec<RefreshEvent>>> {
+    ) -> Result<Async<Result<Vec<RefreshEvent>>>> {
-        unimplemented!()
+        Err(MeliError::new("Unimplemented."))
     }
     fn watch(
         &self,

melib/src/backends/maildir/backend.rs

@@ -203,7 +203,7 @@ impl MailBackend for MaildirType {
         &mut self,
         folder_hash: FolderHash,
         sender: RefreshEventConsumer,
-    ) -> Async<Result<Vec<RefreshEvent>>> {
+    ) -> Result<Async<Result<Vec<RefreshEvent>>>> {
         let w = AsyncBuilder::new();
         let cache_dir = xdg::BaseDirectories::with_profile("meli", &self.name).unwrap();
 
@@ -327,7 +327,7 @@ impl MailBackend for MaildirType {
                 }
             })
         };
-        w.build(handle)
+        Ok(w.build(handle))
     }
     fn watch(
         &self,

ui/src/components/mail/listing.rs

@@ -676,10 +676,16 @@ impl Component for Listing {
             UIEvent::Input(ref key)
                 if shortcut!(key == shortcuts[Listing::DESCRIPTION]["refresh"]) =>
             {
-                let folder_hash =
-                    context.accounts[self.cursor_pos.0].folders_order[self.cursor_pos.1];
                 let account = &mut context.accounts[self.cursor_pos.0];
-                account.refresh(folder_hash);
+                if let Some(&folder_hash) = account.folders_order.get(self.cursor_pos.1) {
+                    if let Err(err) = account.refresh(folder_hash) {
+                        context.replies.push_back(UIEvent::Notification(
+                            Some("Could not refresh.".to_string()),
+                            err.to_string(),
+                            Some(NotificationType::INFO),
+                        ));
+                    }
+                }
                 return true;
             }
             UIEvent::StartupCheck(_) => {

ui/src/conf/accounts.rs

@@ -699,13 +699,14 @@ impl Account {
         }
         None
     }
-    pub fn refresh(&mut self, folder_hash: FolderHash) {
+    pub fn refresh(&mut self, folder_hash: FolderHash) -> Result<()> {
         let sender_ = self.sender.clone();
         let r = RefreshEventConsumer::new(Box::new(move |r| {
             sender_.send(ThreadEvent::from(r)).unwrap();
         }));
-        let mut h = self.backend.write().unwrap().refresh(folder_hash, r);
+        let mut h = self.backend.write().unwrap().refresh(folder_hash, r)?;
         self.work_context.new_work.send(h.work().unwrap()).unwrap();
+        Ok(())
     }
     pub fn watch(&self) {
         if self.settings.account().manual_refresh {