server: Reintroduce TRYCREATE response for APPEND (and now COPY)

Was accidentally removed when moving CreateMessage.
Also it was never present for COPY so it was added there
along the way.

memory backend is also updated to conform with that and
return backend.ErrNoSuchMailbox.

backend/memory/user.go

@@ -121,7 +121,7 @@ func (u *User) CreateMessage(mboxName string, flags []string, date time.Time, bo
 
 func (u *User) CreateMailbox(name string) error {
  if _, ok := u.mailboxes[name]; ok {
- return errors.New("Mailbox already exists")
+ return backend.ErrMailboxAlreadyExists
  }
 
  u.mailboxes[name] = &Mailbox{name: name, user: u}
@@ -133,7 +133,7 @@ func (u *User) DeleteMailbox(name string) error {
  return errors.New("Cannot delete INBOX")
  }
  if _, ok := u.mailboxes[name]; !ok {
- return errors.New("No such mailbox")
+ return backend.ErrNoSuchMailbox
  }
 
  delete(u.mailboxes, name)
@@ -143,7 +143,7 @@ func (u *User) DeleteMailbox(name string) error {
 func (u *User) RenameMailbox(existingName, newName string) error {
  mbox, ok := u.mailboxes[existingName]
  if !ok {
- return errors.New("No such mailbox")
+ return backend.ErrNoSuchMailbox
  }
 
  u.mailboxes[newName] = &Mailbox{

server/cmd_auth.go

@@ -4,6 +4,7 @@ import (
  "errors"
 
  "github.com/emersion/go-imap"
+ "github.com/emersion/go-imap/backend"
  "github.com/emersion/go-imap/commands"
  "github.com/emersion/go-imap/responses"
 )
@@ -216,6 +217,13 @@ func (cmd *Append) Handle(conn Conn) error {
  }
 
  if err := ctx.User.CreateMessage(cmd.Mailbox, cmd.Flags, cmd.Date, cmd.Message); err != nil {
+ if err == backend.ErrNoSuchMailbox {
+ return ErrStatusResp(&imap.StatusResp{
+ Type: imap.StatusRespNo,
+ Code: imap.CodeTryCreate,
+ Info: "No such mailbox",
+ })
+ }
  return err
  }
 

server/cmd_selected.go

@@ -4,6 +4,7 @@ import (
  "errors"
 
  "github.com/emersion/go-imap"
+ "github.com/emersion/go-imap/backend"
  "github.com/emersion/go-imap/commands"
  "github.com/emersion/go-imap/responses"
 )
@@ -214,7 +215,18 @@ func (cmd *Copy) handle(uid bool, conn Conn) error {
  return ErrNoMailboxSelected
  }
 
- return ctx.Mailbox.CopyMessages(uid, cmd.SeqSet, cmd.Mailbox)
+ err := ctx.Mailbox.CopyMessages(uid, cmd.SeqSet, cmd.Mailbox)
+ if err != nil {
+ if err == backend.ErrNoSuchMailbox {
+ return ErrStatusResp(&imap.StatusResp{
+ Type: imap.StatusRespNo,
+ Code: imap.CodeTryCreate,
+ Info: "No such mailbox",
+ })
+ }
+ return err
+ }
+ return nil
 }
 
 func (cmd *Copy) Handle(conn Conn) error {