Notmuch: be resilient to config errors

Right now notmuch panics if something goes wrong in the configure event.
This patch checks for that and returns an error instead, so that we can at least
get the UI up and running (and all the other accounts)

The experience will be completely degraded until another configure event occurs.

worker/notmuch/worker.go

@@ -32,6 +32,7 @@ type worker struct {
 	uidStore            *uidstore.Store
 	nameQueryMap        map[string]string
 	db                  *notmuch.DB
+	setupErr            error
 	currentSortCriteria []*types.SortCriterion
 }
 
@@ -69,6 +70,14 @@ func (w *worker) err(msg types.WorkerMessage, err error) {
 	}, nil)
 }
 func (w *worker) handleMessage(msg types.WorkerMessage) error {
+	if w.setupErr != nil {
+		// only configure can recover from a config error, bail for everything else
+		_, isConfigure := msg.(*types.Configure)
+		if !isConfigure {
+			return w.setupErr
+		}
+	}
+
 	switch msg := msg.(type) {
 	case *types.Unsupported:
 		// No-op
@@ -109,6 +118,15 @@ func (w *worker) handleMessage(msg types.WorkerMessage) error {
 }
 
 func (w *worker) handleConfigure(msg *types.Configure) error {
+	var err error
+	defer func() {
+		if err == nil {
+			w.setupErr = nil
+			return
+		}
+		w.setupErr = fmt.Errorf("notmuch: %v", err)
+	}()
+
 	u, err := url.Parse(msg.Config.Source)
 	if err != nil {
 		w.w.Logger.Printf("error configuring notmuch worker: %v", err)
@@ -120,8 +138,9 @@ func (w *worker) handleConfigure(msg *types.Configure) error {
 	}
 	pathToDB := filepath.Join(home, u.Path)
 	w.uidStore = uidstore.NewStore()
-	if err = w.loadQueryMap(msg.Config); err != nil {
+	err = w.loadQueryMap(msg.Config)
-		return fmt.Errorf("could not load query map: %v", err)
+	if err != nil {
+		return fmt.Errorf("could not load query map configuration: %v", err)
 	}
 	excludedTags := w.loadExcludeTags(msg.Config)
 	w.db = notmuch.NewDB(pathToDB, excludedTags, w.w.Logger)
@@ -393,7 +412,7 @@ func (w *worker) loadQueryMap(acctConfig *config.AccountConfig) error {
 
 		split := strings.SplitN(line, "=", 2)
 		if len(split) != 2 {
-			return fmt.Errorf("invalid line %q, want name=query", line)
+			return fmt.Errorf("%v: invalid line %q, want name=query", file, line)
 		}
 		w.nameQueryMap[split[0]] = split[1]
 	}