fix UID assignment with some non-UIDPLUS servers

the seznam.cz IMAP server seems very eager to send UIDNEXT responses
despite not supporting UIDPLUS. this doesn't appear to be a particularly
sensible combination, but it's valid nonetheless.

however, that means that we need to save the UIDNEXT value before we
start storing messages, lest imap_find_new_msgs() will simply overlook
them. we do that outside the driver, in an already present field - this
actually makes the main path more consistent with the journal recovery
path.

analysis by Tomas Tintera <trosos@seznam.cz>.

REFMAIL: 20141220215032.GA10115@kyvadlo.trosos.seznam.cz

src/driver.h

@@ -192,7 +192,7 @@ struct driver {
 	/* Index the messages which have newly appeared in the mailbox, including their
 	 * temporary UID headers. This is needed if store_msg() does not guarantee returning
 	 * a UID; otherwise the driver needs to implement only the OPEN_FIND flag. */
-	void (*find_new_msgs)( store_t *ctx,
+	void (*find_new_msgs)( store_t *ctx, int newuid,
 	                       void (*cb)( int sts, void *aux ), void *aux );
 
 	/* Add/remove the named flags to/from the given message. The message may be either

src/drv_imap.c

@@ -153,6 +153,11 @@ struct imap_cmd_out_uid {
 	int out_uid;
 };
 
+struct imap_cmd_find_new {
+	struct imap_cmd_simple gen;
+	int uid;
+};
+
 struct imap_cmd_refcounted_state {
 	void (*callback)( int sts, void *aux );
 	void *callback_aux;
@@ -2158,28 +2163,30 @@ imap_store_msg_p2( imap_store_t *ctx ATTR_UNUSED, struct imap_cmd *cmd, int resp
 static void imap_find_new_msgs_p2( imap_store_t *, struct imap_cmd *, int );
 
 static void
-imap_find_new_msgs( store_t *gctx,
+imap_find_new_msgs( store_t *gctx, int newuid,
                     void (*cb)( int sts, void *aux ), void *aux )
 {
 	imap_store_t *ctx = (imap_store_t *)gctx;
-	struct imap_cmd_simple *cmd;
+	struct imap_cmd_find_new *cmd;
 
-	INIT_IMAP_CMD(imap_cmd_simple, cmd, cb, aux)
-	imap_exec( (imap_store_t *)ctx, &cmd->gen, imap_find_new_msgs_p2, "CHECK" );
+	INIT_IMAP_CMD_X(imap_cmd_find_new, cmd, cb, aux)
+	cmd->uid = newuid;
+	imap_exec( (imap_store_t *)ctx, &cmd->gen.gen, imap_find_new_msgs_p2, "CHECK" );
 }
 
 static void
 imap_find_new_msgs_p2( imap_store_t *ctx, struct imap_cmd *gcmd, int response )
 {
-	struct imap_cmd_simple *cmdp = (struct imap_cmd_simple *)gcmd, *cmd;
+	struct imap_cmd_find_new *cmdp = (struct imap_cmd_find_new *)gcmd;
+	struct imap_cmd_simple *cmd;
 
 	if (response != RESP_OK) {
 		imap_done_simple_box( ctx, gcmd, response );
 		return;
 	}
-	INIT_IMAP_CMD(imap_cmd_simple, cmd, cmdp->callback, cmdp->callback_aux)
+	INIT_IMAP_CMD(imap_cmd_simple, cmd, cmdp->gen.callback, cmdp->gen.callback_aux)
 	imap_exec( (imap_store_t *)ctx, &cmd->gen, imap_done_simple_box,
-	           "UID FETCH %d:1000000000 (UID BODY.PEEK[HEADER.FIELDS (X-TUID)])", ctx->gen.uidnext );
+	           "UID FETCH %d:1000000000 (UID BODY.PEEK[HEADER.FIELDS (X-TUID)])", cmdp->uid );
 }
 
 /******************* imap_list *******************/

src/drv_maildir.c

@@ -1292,7 +1292,7 @@ maildir_store_msg( store_t *gctx, msg_data_t *data, int to_trash,
 }
 
 static void
-maildir_find_new_msgs( store_t *gctx ATTR_UNUSED,
+maildir_find_new_msgs( store_t *gctx ATTR_UNUSED, int newuid ATTR_UNUSED,
                        void (*cb)( int sts, void *aux ) ATTR_UNUSED, void *aux ATTR_UNUSED )
 {
 	assert( !"maildir_find_new_msgs is not supposed to be called" );

src/sync.c

@@ -1506,7 +1506,8 @@ box_loaded( int sts, void *aux )
 	if (UseFSync)
 		fdatasync( fileno( svars->jfp ) );
 	for (t = 0; t < 2; t++) {
-		Fprintf( svars->jfp, "%c %d\n", "{}"[t], svars->ctx[t]->uidnext );
+		svars->newuid[t] = svars->ctx[t]->uidnext;
+		Fprintf( svars->jfp, "%c %d\n", "{}"[t], svars->newuid[t] );
 		for (tmsg = svars->ctx[1-t]->msgs; tmsg; tmsg = tmsg->next) {
 			if ((srec = tmsg->srec) && srec->tuid[0]) {
 				svars->new_total[t]++;
@@ -1604,7 +1605,7 @@ msgs_copied( sync_vars_t *svars, int t )
 
 	if (svars->state[t] & ST_FIND_NEW) {
 		debug( "finding just copied messages on %s\n", str_ms[t] );
-		svars->drv[t]->find_new_msgs( svars->ctx[t], msgs_found_new, AUX );
+		svars->drv[t]->find_new_msgs( svars->ctx[t], svars->newuid[t], msgs_found_new, AUX );
 	} else {
 		msgs_new_done( svars, t );
 	}