[ENSCORESW-577]. Additional lookup would not work if it was the first call.

The code did not attempt to build the additional lookup before fetching from
it. Our solution is to switch to requesting the cache in get_????_additional_lookup()
which will trigger the building of the additional lookup.

modules/Bio/EnsEMBL/DBSQL/Support/FullIdCache.pm

@@ -125,6 +125,7 @@ sub clear_cache {
 
 sub get_by_additional_lookup {
   my ($self, $key, $value) = @_;
+  $self->cache(); # trigger cache building
   my $additional_lookup = $self->_additional_lookup();
   if(exists $additional_lookup->{$key}) {
     if(exists $additional_lookup->{$key}->{$value}) {
@@ -158,6 +159,7 @@ sub get_by_additional_lookup {
 
 sub get_all_by_additional_lookup {
   my ($self, $key, $value) = @_;
+  $self->cache(); # trigger cache building
   my $additional_lookup = $self->_additional_lookup();
   if(exists $additional_lookup->{$key}) {
     if(exists $additional_lookup->{$key}->{$value}) {

modules/t/fullIdCaching.t

@@ -105,6 +105,16 @@ sub BEGIN {
 
     dies_ok { $cache->get_by_additional_lookup('biotype', 'protein_coding') } 'Expect to die as the query will return more than one value';
 
+    #Clear the cache and make sure that we can still retrieve by additional values
+    {
+      $cache->clear_cache();
+      my $db_id = $protein_coding_genes->[0]->dbID();
+      my $fetched_gene = $cache->get_by_additional_lookup('dbID', $db_id);
+      ok(defined $fetched_gene, 'Checking we got a gene back if we fetched using additional lookups alone');
+      cmp_ok($fetched_gene->dbID(), '==', $db_id, 'Checking we got a gene back if we fetched using additional lookups alone');
+    }
+
+
     $cache->remove($individual_gene->dbID());
     my $new_protein_coding_genes = $cache->get_all_by_additional_lookup('biotype', 'protein_coding');