msgstore: post MessageInfo on erroneous fetch

When errors occur during a fetch header request, the requested headers
are deleted from pending and no information is given to the UI. Spinners
keep spinning, and ultimately as the view is refreshed, the headers are
fetched again. This can lead to infinite loops, and extremely long logs.

Update the store with a MessageInfo message when an error is received.
Have the UI display that the header couldn't be fetched in the message
list.

Signed-off-by: Tim Culverhouse <tim@timculverhouse.com>
Acked-by: Robin Jarry <robin@jarry.cc>

lib/format/format.go

@@ -83,6 +83,10 @@ func ParseMessageFormat(format string, timeFmt string, thisDayTimeFmt string,
 	thisWeekTimeFmt string, thisYearTimeFmt string, ctx Ctx) (
 	string, []interface{}, error,
 ) {
+	if ctx.MsgInfo.Error != nil {
+		return "", nil,
+			errors.New("(unable to fetch header)")
+	}
 	retval := make([]byte, 0, len(format))
 	var args []interface{}
 

lib/msgstore.go

@@ -112,8 +112,9 @@ func (store *MessageStore) FetchHeaders(uids []uint32,
 	}
 	if len(toFetch) > 0 {
 		store.worker.PostAction(&types.FetchMessageHeaders{Uids: toFetch}, func(msg types.WorkerMessage) {
-			if _, ok := msg.(*types.Error); ok {
+			if msg, ok := msg.(*types.Error); ok {
 				for _, uid := range toFetch {
+					store.postInvalidMessageInfo(uid, msg.Error)
 					delete(store.pendingHeaders, uid)
 				}
 			}
@@ -124,6 +125,17 @@ func (store *MessageStore) FetchHeaders(uids []uint32,
 	}
 }
 
+func (store *MessageStore) postInvalidMessageInfo(uid uint32, err error) {
+	logging.Errorf("Unable to fetch header %d: %w", uid, err)
+	info := &models.MessageInfo{
+		Envelope: &models.Envelope{},
+		Flags:    []models.Flag{models.SeenFlag},
+		Uid:      uid,
+		Error:    err,
+	}
+	store.Update(&types.MessageInfo{Info: info})
+}
+
 func (store *MessageStore) FetchFull(uids []uint32, cb func(*types.FullMessage)) {
 	// TODO: this could be optimized by pre-allocating toFetch and trimming it
 	// at the end. In practice we expect to get most messages back in one frame.