Normalize language tags to lower case when creating an i18n datatype or compound literal.

Author: gkellogg

lib/json/ld/to_rdf.rb

@@ -50,11 +50,11 @@ def item_to_rdf(item, graph_name: nil, &block)
             # Either serialize using a datatype, or a compound-literal
             case @options[:rdfDirection]
             when 'i18n-datatype'
-              datatype = RDF::URI("https://www.w3.org/ns/i18n##{item.fetch('@language', '')}_#{item['@direction']}")
+              datatype = RDF::URI("https://www.w3.org/ns/i18n##{item.fetch('@language', '').downcase}_#{item['@direction']}")
             when 'compound-literal'
               cl = RDF::Node.new
               yield RDF::Statement(cl, RDF.value, item['@value'].to_s)
-              yield RDF::Statement(cl, RDF.to_uri + 'language', item['@language']) if item['@language']
+              yield RDF::Statement(cl, RDF.to_uri + 'language', item['@language'].downcase) if item['@language']
               yield RDF::Statement(cl, RDF.to_uri + 'direction', item['@direction'])
               return cl
             end

spec/to_rdf_spec.rb

@@ -1133,7 +1133,7 @@
           ],
           "en-US rtl": [
             %q({"http://example.org/label": {"@value": "en-US", "@language": "en-US", "@direction": "rtl"}}),
-            %q(_:a <http://example.org/label> "en-US"^^<https://www.w3.org/ns/i18n#en-US_rtl> .)
+            %q(_:a <http://example.org/label> "en-US"^^<https://www.w3.org/ns/i18n#en-us_rtl> .)
           ]
         }.each do |title, (js, ttl)|
           it title do
@@ -1161,7 +1161,7 @@
               @prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
               _:a <http://example.org/label> [
                 rdf:value "en-US";
-                rdf:language "en-US";
+                rdf:language "en-us";
                 rdf:direction "rtl"
               ] .
             )