Gracefully handle empty mailboxes in mu_msgset_parse_imap

* libmailutils/msgset/parse.c (MU_MSGSET_EMPTY): New constant.
(parse_msgrange): Don't add any ranges if mode is set to
MU_MSGSET_EMPTY.
(mu_msgset_parse_imap): Force MU_MSGSET_EMPTY mode if the mailbox
is empty.
* libmailutils/msgset/print.c (mu_msgset_print): Handle empty message
sets.
* libmailutils/msgset/trans.c (_mu_msgset_translate_pair): Initialize
variable.
* libmailutils/tests/Makefile.am (msgset_LDADD): New variable.
* libmailutils/tests/msgset.c (parse_msgset): Take mailbox as first
argument.
(main): New option -mailbox

@@ -26,6 +26,9 @@
 #include <mailutils/msgset.h>
 #include <mailutils/sys/msgset.h>
 
+/* Special translation mode, indicating that the mailbox is empty */
+#define MU_MSGSET_EMPTY -1
+
 /* This structure keeps parser state while parsing message set. */
 struct parse_msgnum_env
 {
@@ -33,7 +36,7 @@ struct parse_msgnum_env
   size_t minval;         /* Min. sequence number or UID */
   size_t maxval;         /* Max. sequence number or UID */
   mu_msgset_t msgset;    /* Message set being built. */
-  int mode;              /* Operation mode (num/uid) */
+  int mode;              /* Operation mode (num/uid/dry_run) */
 };
 
 /* Get a single message number/UID from env->s and store it into *PN.
@@ -96,6 +99,8 @@ parse_msgrange (struct parse_msgnum_env *env)
       msgrange.msg_beg = tmp;
     }
 
+  if (env->mode == MU_MSGSET_EMPTY)
+    return 0;
   return mu_msgset_add_range (env->msgset, msgrange.msg_beg, msgrange.msg_end,
 			      env->mode);
 }
@@ -131,7 +136,11 @@ mu_msgset_parse_imap (mu_msgset_t mset, int mode, const char *s, char **end)
       rc = mu_mailbox_messages_count (mset->mbox, &lastmsgno);
       if (rc == 0)
 	{
-	  if (mode == MU_MSGSET_UID)
+	  if (lastmsgno == 0)
+	    {
+	      env.mode = MU_MSGSET_EMPTY;
+	    }
+	  else if (mode == MU_MSGSET_UID)
 	    {
 	      rc = mu_mailbox_translate (mset->mbox, MU_MAILBOX_MSGNO_TO_UID,
 					 lastmsgno, &env.maxval);

@@ -64,7 +64,7 @@ mu_msgset_print (mu_stream_t str, mu_msgset_t mset)
   int rc;
   
   if (mu_list_is_empty (mset->list))
-    return MU_ERR_NOENT;
+    return mu_stream_printf (str, "%s", "nil");
   rc = mu_msgset_aggregate (mset);
   if (rc)
     return rc;

@@ -30,7 +30,7 @@ _mu_msgset_translate_pair (mu_msgset_t mset, int mode,
   if (mode != _MU_MSGSET_MODE (mset->flags) && mset->mbox)
     {
       int cmd, rc;
-      size_t n;
+      size_t n = 1;
       size_t beg = *pbeg;
       size_t end = *pend;
       

@@ -69,6 +69,12 @@ noinst_PROGRAMS = \
 
 LDADD = ${MU_LIB_MAILUTILS}
 
+msgset_LDADD = \
+ ${MU_LIB_MBOX}\
+ ${MU_LIB_MH}\
+ ${MU_LIB_MAILDIR}\
+ ${MU_LIB_MAILUTILS}
+
 EXTRA_DIST += Encode Decode Wicketfile
 
 ## ------------ ##

@@ -53,16 +53,16 @@ parse_msgrange (char *arg, struct mu_msgrange *range)
 }
 
 mu_msgset_t
-parse_msgset (const char *arg)
+parse_msgset (mu_mailbox_t mbox, const char *arg)
 {
   int rc;
   mu_msgset_t msgset;
   char *end;
 
-  MU_ASSERT (mu_msgset_create (&msgset, NULL, MU_MSGSET_NUM));
+  MU_ASSERT (mu_msgset_create (&msgset, mbox, MU_MSGSET_NUM));
   if (arg)
     {
-      rc = mu_msgset_parse_imap (msgset, MU_MSGSET_NUM, arg, &end);
+      rc = mu_msgset_parse_imap (msgset, MU_MSGSET_UID, arg, &end);
       if (rc)
 	{
 	  mu_error ("mu_msgset_parse_imap: %s near %s",
@@ -79,26 +79,33 @@ main (int argc, char **argv)
   int i;
   char *msgset_string = NULL;
   mu_msgset_t msgset;
+  mu_mailbox_t mbox = NULL;
   
   mu_set_program_name (argv[0]);
+  mu_register_local_mbox_formats ();
   for (i = 1; i < argc; i++)
     {
       char *arg = argv[i];
 
       if (strcmp (arg, "-h") == 0 || strcmp (arg, "-help") == 0)
 	{
-	  mu_printf ("usage: %s [-msgset=SET] [-add=X[:Y]] [-del=X[:Y]] "
+	  mu_printf ("usage: %s [-mailbox=PATH] [-msgset=SET] [-add=X[:Y]] [-del=X[:Y]] "
 		     "[-addset=SET] [-delset=SET] ...\n",
 		     mu_program_name);
 	  return 0;
 	}
       else if (strncmp (arg, "-msgset=", 8) == 0)
 	msgset_string = arg + 8;
+      else if (strncmp (arg, "-mailbox=", 9) == 0)
+	{
+	  MU_ASSERT (mu_mailbox_create_default (&mbox, arg + 9));
+	  MU_ASSERT (mu_mailbox_open (mbox, MU_STREAM_READ));
+	}
       else
 	break;
     }
 
-  msgset = parse_msgset (msgset_string);
+  msgset = parse_msgset (mbox, msgset_string);
   
   for (; i < argc; i++)
     {
@@ -119,7 +126,7 @@ main (int argc, char **argv)
 	}
       else if (strncmp (arg, "-addset=", 8) == 0)
 	{
-	  mu_msgset_t tset = parse_msgset (arg + 8);
+	  mu_msgset_t tset = parse_msgset (mbox, arg + 8);
 	  if (!msgset)
 	    msgset = tset;
 	  else
@@ -130,7 +137,7 @@ main (int argc, char **argv)
 	}
       else if (strncmp (arg, "-subset=", 8) == 0)
 	{
-	  mu_msgset_t tset = parse_msgset (arg + 8);
+	  mu_msgset_t tset = parse_msgset (mbox, arg + 8);
 	  if (!msgset)
 	    {
 	      mu_error ("no initial message set");