Bug 33277: Add comments and missing thesauri

Signed-off-by: Frank Hansen <frank.hansen@ub.lu.se>

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>

C4/Heading.pm

@@ -202,6 +202,8 @@ sub _search {
     my @operator;
     my @value;
 
+    # FIXME: We specify values for @and_or and @excluding
+    # but these fields are not used anywhere and should be removed
     if ($index) {
         push @marclist, $index;
         push @and_or,   'AND';

C4/Heading/MARC21.pm

@@ -359,6 +359,11 @@ sub _get_subject_thesaurus {
     my $field = shift;
     my $ind2  = $field->indicator(2);
 
+    # NOTE: sears and aat do not appear
+    # here as they do not have indicator values
+    # though the 008 in the authority records
+    # do have values for them
+
     my $thesaurus = "notdefined";
     if ( $ind2 eq '0' ) {
         $thesaurus = "lcsh";

Koha/SearchEngine/Elasticsearch/QueryBuilder.pm

@@ -564,14 +564,20 @@ our $koha_to_index_name = {
     all             => ''
 };
 
+# Note that sears and aat map to 008/11 values here
+# but don't appear in C4/Headin/MARC21 thesaurus
+# because they don't have values in controlled field indicators
+# https://www.loc.gov/marc/authority/ad008.html
 our $thesaurus_to_value = {
-   lcsh => 'a',
-   lcac => 'b',
-   mesh => 'c',
-   nal  => 'd',
+   lcsh  => 'a',
+   lcac  => 'b',
+   mesh  => 'c',
+   nal   => 'd',
    notspecified => 'n',
-   cash => 'k',
-   rvm => 'v',
+   cash  => 'k',
+   rvm   => 'v',
+   aat   => 'r',
+   sears => 's'
 };
 
 sub build_authorities_query_compat {

t/db_dependent/Heading.t

@@ -69,6 +69,9 @@ subtest "_search tests" => sub {
 
     t::lib::Mocks::mock_preference('marcflavour', 'MARC21');
     t::lib::Mocks::mock_preference('SearchEngine', 'Elasticsearch');
+    # NOTE: We are testing solely against ES here to make the assumptions simpler while testing
+    # C4/Headings code specifically. The actual query building and searching code should
+    # be covered in other test files
     my $search = Test::MockModule->new('Koha::SearchEngine::Elasticsearch::Search');
 
     $search->mock('search_auth_compat', sub {