jmap: invalidate cache if mailbox state is not consistent

We weren't checking if the cached state was the same as the remote state
before reading it. This led to aerc not knowing about new mailboxes on
the remote.

Signed-off-by: Tristan Partin <tristan@partin.io>
Acked-by: Robin Jarry <robin@jarry.cc>

worker/jmap/directories.go

@@ -21,21 +21,38 @@ func (w *JMAPWorker) handleListDirectories(msg *types.ListDirectories) error {
 
 	mboxes = make(map[jmap.ID]*mailbox.Mailbox)
 
-	mboxIds, err := w.cache.GetMailboxList()
-	if err == nil {
-		for _, id := range mboxIds {
-			mbox, err := w.cache.GetMailbox(id)
-			if err != nil {
-				w.w.Warnf("GetMailbox: %s", err)
-				missing = append(missing, id)
-				continue
+	currentMailboxState, err := w.getMailboxState()
+	if err != nil {
+		return err
+	}
+
+	// If we can't get the cached mailbox state, at worst, we will just
+	// query information we might already know
+	cachedMailboxState, err := w.cache.GetMailboxState()
+	if err != nil {
+		w.w.Warnf("PutMailboxState: %s", err)
+	}
+
+	consistentMailboxState := currentMailboxState == cachedMailboxState
+
+	// If we have a consistent state, check the cache
+	if consistentMailboxState {
+		mboxIds, err := w.cache.GetMailboxList()
+		if err == nil {
+			for _, id := range mboxIds {
+				mbox, err := w.cache.GetMailbox(id)
+				if err != nil {
+					w.w.Warnf("GetMailbox: %s", err)
+					missing = append(missing, id)
+					continue
+				}
+				mboxes[id] = mbox
+				ids = append(ids, id)
 			}
-			mboxes[id] = mbox
-			ids = append(ids, id)
 		}
 	}
 
-	if err != nil || len(missing) > 0 {
+	if !consistentMailboxState || len(missing) > 0 {
 		var req jmap.Request
 
 		req.Invoke(&mailbox.Get{Account: w.accountId})

worker/jmap/state.go

@@ -0,0 +1,29 @@
+package jmap
+
+import (
+	"git.sr.ht/~rockorager/go-jmap"
+	"git.sr.ht/~rockorager/go-jmap/mail/mailbox"
+)
+
+func (w *JMAPWorker) getMailboxState() (string, error) {
+	var req jmap.Request
+
+	req.Invoke(&mailbox.Get{Account: w.accountId, IDs: make([]jmap.ID, 0)})
+	resp, err := w.Do(&req)
+	if err != nil {
+		return "", err
+	}
+
+	for _, inv := range resp.Responses {
+		switch r := inv.Args.(type) {
+		case *mailbox.GetResponse:
+			return r.State, nil
+		case *jmap.MethodError:
+			return "", wrapMethodError(r)
+
+		}
+	}
+
+	// This should be an impossibility
+	return "", nil
+}