When expanding value that might return an array, make sure to concat rather than append.

Author: gkellogg

lib/json/ld/expand.rb

@@ -32,7 +32,11 @@ def expand(input, active_property, context, ordered: true)
           raise JsonLdError::ListOfLists,
                 "A list may not contain another list" if
                 is_list && (v.is_a?(Array) || list?(v))
-          memo << v unless v.nil?
+          case v
+          when nil then nil
+          when Array then memo.concat(v)
+          else            memo << v
+          end
         end
 
         value

spec/expand_spec.rb

@@ -637,6 +637,29 @@
             "http://example.com/foo" => []
           }]
         },
+        "Free-floating values in sets" => {
+          input: %({
+            "@context": {"property": "http://example.com/property"},
+            "@graph": [{
+                "@set": [
+                    "free-floating strings in set objects are removed",
+                    {"@id": "http://example.com/free-floating-node"},
+                    {
+                        "@id": "http://example.com/node",
+                        "property": "nodes with properties are not removed"
+                    }
+                ]
+            }]
+          }),
+          output: %([{
+            "@id": "http://example.com/node",
+            "http://example.com/property": [
+              {
+                "@value": "nodes with properties are not removed"
+              }
+            ]
+          }])
+        }
       }.each do |title, params|
         it(title) {run_expand params}
       end