Dereference child schemas for schemas without ref

If you have a subschema that says that it is expanded, it
might actually have children that have not yet been expanded.
If the subschema did not have a reference, we were not recursing
any further.

lib/json_schema/reference_expander.rb

@@ -87,6 +87,18 @@ def build_schema_paths(uri, schema)
     def dereference(ref_schema, ref_stack)
       ref = ref_schema.reference
 
+      # Some schemas don't have a reference, but do
+      # have children. If that's the case, we need to
+      # dereference the subschemas.
+      if !ref
+        schema_children(ref_schema) do |subschema|
+          next unless subschema.reference
+
+          dereference(subschema, ref_stack)
+        end
+        return true
+      end
+
       # detects a reference cycle
       if ref_stack.include?(ref)
         message = %{Reference loop detected: #{ref_stack.sort.join(", ")}.}
@@ -114,9 +126,12 @@ def dereference(ref_schema, ref_stack)
           # schema as the reference schema.
           next if ref_schema == subschema
 
-          next if subschema.expanded?
-
           if subschema.reference
+            # If the subschema has a reference, then
+            # we don't need to recurse if the schema is
+            # already expanded.
+            next if subschema.expanded?
+
             if !subschema.reference.uri
               # the subschema's ref is local to the file that the
               # subschema is in; however since there's no URI

test/json_schema/reference_expander_test.rb

@@ -320,6 +320,59 @@
     assert_equal 3, schema1.properties["foo"].properties["omg"].max_length
   end
 
+  it "it handles oneOf with nested references to an external schema" do
+    sample1 = {
+      "$schema" => "http://json-schema.org/draft-04/hyper-schema",
+      "type" => "object",
+      "properties" => {
+        "foo" => {
+          "$ref" => "http://json-schema.org/b.json#"
+        }
+      }
+    }
+    schema1 = JsonSchema::Parser.new.parse!(sample1)
+    schema1.uri = "http://json-schema.org/a.json"
+
+    sample2 = {
+      "$schema" => "http://json-schema.org/draft-04/hyper-schema",
+      "type" => "object",
+      "properties" => {
+        "bar" => {
+          "oneOf" => [
+            {"type" => "null"},
+            {"$ref" => "http://json-schema.org/c.json#"}
+          ]
+        }
+      },
+    }
+    schema2 = JsonSchema::Parser.new.parse!(sample2)
+    schema2.uri = "http://json-schema.org/b.json"
+
+    sample3 = {
+      "$schema" => "http://json-schema.org/draft-04/hyper-schema",
+      "type" => "object",
+      "properties" => {
+        "baz" => {
+          "type" => "string",
+          "maxLength" => 3
+        }
+      }
+    }
+    schema3 = JsonSchema::Parser.new.parse!(sample3)
+    schema3.uri = "http://json-schema.org/c.json"
+
+    # Initialize a store and add our schema to it.
+    store = JsonSchema::DocumentStore.new
+    store.add_schema(schema1)
+    store.add_schema(schema2)
+    store.add_schema(schema3)
+
+    expander = JsonSchema::ReferenceExpander.new
+    expander.expand(schema1, store: store)
+
+    assert_equal 3, schema1.properties["foo"].properties["bar"].one_of[1].properties["baz"].max_length
+  end
+
   it "expands a schema with a reference to an external schema with a nested local property reference" do
     sample1 = {
       "$schema" => "http://json-schema.org/draft-04/hyper-schema",