pgp: fail gracefully from email decryption

Aerc panics when there's an error on email decryption.
Instead, an error message should be shown.

commands/account/view.go

@@ -39,7 +39,11 @@ func (ViewMessage) Execute(aerc *widgets.Aerc, args []string) error {
 		return nil
 	}
 	lib.NewMessageStoreView(msg, store, aerc.DecryptKeys,
-		func(view lib.MessageView) {
+		func(view lib.MessageView, err error) {
+			if err != nil {
+				aerc.PushError(err.Error())
+				return
+			}
 			viewer := widgets.NewMessageViewer(acct, aerc.Config(), view)
 			aerc.NewTab(viewer, msg.Envelope.Subject)
 		})

commands/msg/delete.go

@@ -66,7 +66,11 @@ func (Delete) Execute(aerc *widgets.Aerc, args []string) error {
 				return nil
 			}
 			lib.NewMessageStoreView(next, store, aerc.DecryptKeys,
-				func(view lib.MessageView) {
+				func(view lib.MessageView, err error) {
+					if err != nil {
+						aerc.PushError(err.Error())
+						return
+					}
 					nextMv := widgets.NewMessageViewer(acct, aerc.Config(), view)
 					aerc.ReplaceTab(mv, nextMv, next.Envelope.Subject)
 				})

commands/msgview/next.go

@@ -38,7 +38,11 @@ func (NextPrevMsg) Execute(aerc *widgets.Aerc, args []string) error {
 		return nil
 	}
 	lib.NewMessageStoreView(nextMsg, store, aerc.DecryptKeys,
-		func(view lib.MessageView) {
+		func(view lib.MessageView, err error) {
+			if err != nil {
+				aerc.PushError(err.Error())
+				return
+			}
 			nextMv := widgets.NewMessageViewer(acct, aerc.Config(), view)
 			aerc.ReplaceTab(mv, nextMv, nextMsg.Envelope.Subject)
 		})

lib/messageview.go

@@ -59,7 +59,7 @@ type MessageStoreView struct {
 
 func NewMessageStoreView(messageInfo *models.MessageInfo,
 	store *MessageStore, decryptKeys openpgp.PromptFunction,
-	cb func(MessageView)) {
+	cb func(MessageView, error)) {
 
 	msv := &MessageStoreView{messageInfo, store,
 		nil, nil, messageInfo.BodyStructure}
@@ -69,26 +69,30 @@ func NewMessageStoreView(messageInfo *models.MessageInfo,
 			reader := fm.Content.Reader
 			pgpReader, err := pgpmail.Read(reader, Keyring, decryptKeys, nil)
 			if err != nil {
-				panic(err)
+				cb(nil, err)
+				return
 			}
 			msv.message, err = ioutil.ReadAll(pgpReader.MessageDetails.UnverifiedBody)
 			if err != nil {
-				panic(err)
+				cb(nil, err)
+				return
 			}
 			decrypted, err := message.Read(bytes.NewBuffer(msv.message))
 			if err != nil {
-				panic(err)
+				cb(nil, err)
+				return
 			}
 			bs, err := lib.ParseEntityStructure(decrypted)
 			if err != nil {
-				panic(err)
+				cb(nil, err)
+				return
 			}
 			msv.bodyStructure = bs
 			msv.details = pgpReader.MessageDetails
-			cb(msv)
+			cb(msv, nil)
 		})
 	} else {
-		cb(msv)
+		cb(msv, nil)
 	}
 	store.Read([]uint32{messageInfo.Uid}, true, nil)
 }

widgets/msglist.go

@@ -166,7 +166,11 @@ func (ml *MessageList) MouseEvent(localX int, localY int, event tcell.Event) {
 					return
 				}
 				lib.NewMessageStoreView(msg, store, ml.aerc.DecryptKeys,
-					func(view lib.MessageView) {
+					func(view lib.MessageView, err error) {
+						if err != nil {
+							ml.aerc.PushError(err.Error())
+							return
+						}
 						viewer := NewMessageViewer(acct, ml.aerc.Config(), view)
 						ml.aerc.NewTab(viewer, msg.Envelope.Subject)
 					})