[PATCH] unionmap error handling

[Roel van Meer]

Hi,

while investigation unexpected bounces, I noticed that the unionmap did not  
handle errors of submaps properly. If a submap generated an error, the  
unionmap would not.

I tested this with an LDAP map, where the LDAP server was *not* reachable.
Configuring virtual_alias_maps as:

 virtual_alias_maps = ldap:/etc/postfix/ldap-virtual.cf

would result in '451 Temporary lookup failure', while configuring it as

 virtual_alias_maps = unionmap:{ldap:/etc/postfix/ldap-virtual.cf}

would result in '550 Recipient address rejected: User unknown in virtual  
alias table'.

The attached patch fixes that, by making the unionmap return the first  
error it gets from one of the submaps.

Thanks,

Roel
diff -pruN a/src/util/dict_union.c b/src/util/dict_union.c
--- a/src/util/dict_union.c     2014-10-21 01:53:04.000000000 +0200
+++ b/src/util/dict_union.c     2016-09-15 11:35:47.669767063 +0200
@@ -81,8 +81,11 @@ static const char *dict_union_lookup(DIC
     for (cpp = dict_union->map_union->argv; (dict_type_name = *cpp) != 0; 
cpp++) {
        if ((map = dict_handle(dict_type_name)) == 0)
            msg_panic("%s: dictionary \"%s\" not found", myname, 
dict_type_name);
-       if ((result = dict_get(map, query)) == 0)
-           continue;
+       result = dict_get(map, query);
+       if (map->error < 0)
+           DICT_ERR_VAL_RETURN(dict, map->error, 0);
+       if (result == 0)
+           return;
        if (VSTRING_LEN(dict_union->re_buf) > 0)
            VSTRING_ADDCH(dict_union->re_buf, ',');
        vstring_strcat(dict_union->re_buf, result);