Don't query stable_id_version for older Ensembl releases

- Avoid retrieving stable_id_version for older Ensembl releases (issue #139).

DESCRIPTION

@@ -1,7 +1,7 @@
 Package: ensembldb
 Type: Package
 Title: Utilities to create and use Ensembl-based annotation databases
-Version: 2.21.2
+Version: 2.21.3
 Authors@R: c(person(given = "Johannes", family = "Rainer",
 	   email = "[email protected]",
 	   role = c("aut", "cre"),

inst/NEWS

@@ -1,3 +1,8 @@
+Changes in version 2.21.3
+
+- Add minimal required Ensembl API version for certain data fields
+  (stable_id_version). Issue https://github.com/jorainer/ensembldb/issues/139
+
 Changes in version 2.21.1
 
 - Since *is circular* flag for chromosomes extracted using the Ensembl Perl API

inst/perl/get_gene_transcript_exon_tables.pl

@@ -1,5 +1,6 @@
 #!/usr/bin/perl
 #####################################
+## version 0.3.9: * Don't query stable_id_version for Ensembl release < 75.
 ## version 0.3.8: * Add column tx_is_canonical to transcript table.
 ## version 0.3.7: * Add column tx_external_name to transcript table.
 ## version 0.3.6: * Add column canonical_transcript to gene table.
@@ -38,6 +39,7 @@
 use List::MoreUtils qw/ uniq /;
 my $script_version = "0.3.7";
 my $min_tsl_version = 87;   ## The minimal required Ensembl version providing support for the tsl method.
+my $min_stable_id_version_version = 87; # minimal Ensembl version for ->stable_id_version
 
 ## connecting to the ENSEMBL data base
 use Bio::EnsEMBL::Registry;
@@ -227,7 +229,10 @@
     if(!defined($gene_external_name)){
       $gene_external_name="";
     }
-    my $gene_id_version = $gene->stable_id_version;
+    my $gene_id_version = "NULL";
+    if ($ensembl_version_num >= $min_stable_id_version_version) {
+	$gene_id_version = $gene->stable_id_version;
+    }
     my $gene_biotype = $gene->biotype;
     my $gene_seq_start = $gene->start;
     my $gene_seq_end = $gene->end;
@@ -270,7 +275,10 @@
 	$tx_cds_end = "NULL";
       }
       my $tx_id = $transcript->stable_id;
-      my $tx_id_version = $transcript->stable_id_version;
+      my $tx_id_version = "NULL";
+      if ($ensembl_version_num >= $min_stable_id_version_version) {
+	  $tx_id_version = $transcript->stable_id_version;
+      }
       my $tx_biotype = $transcript->biotype;
       my $tx_seq_start = $transcript->start;
       my $tx_seq_end = $transcript->end;