Expand references of DocuemntStore schemas

This is a fix for thoughtbot#92.

Calls `expand_references!` on loaded schemas before adding them to the
`DocumentStore`.  This is intended to fix a bug where complex schemas
that include more than one level of cross-file use of `$ref`s are not
being validated correctly.

This commit includes new test cases that reproduce this issue and show
the effectiveness of the proposed fix.

The inspiration for this fix comes from a command included in the
`json_schema` gem.  In that gem, the stand-alone validator command
expands references within schemas before adding them to the store.
It seems reasonable to do the same here.

See https://github.com/brandur/json_schema/blob/20ccb82d7e18140d88ded508edd6c003865c98a0/lib/commands/validate_schema.rb#L92.

lib/json_matchers/matcher.rb

@@ -36,6 +36,10 @@ def build_and_populate_document_store
  map { |schema_path| Parser.new(schema_path).parse }.
  each { |schema| document_store.add_schema(schema) }
 
+ document_store.to_a.each do |_k, schema|
+ schema.expand_references!(store: document_store)
+ end
+
  document_store
  end
  end

spec/factories.rb

@@ -68,6 +68,7 @@
 
  initialize_with do
  FakeSchema.new(name, {
+ "id": "file:/#{name}.json#",
  "$schema": "https://json-schema.org/draft-04/schema#",
  "type": "array",
  "items": { "$ref": "file:/#{items.name}.json#" },

spec/json_matchers/match_json_schema_spec.rb

@@ -202,6 +202,24 @@
  expect(json_as_array).not_to match_json_schema(schema)
  end
 
+ it "validates against a schema that uses nested $refs" do
+ schema = create(:schema, :referencing_locations,
+ items: create(:schema, :referencing_locations))
+ json = build(:response, :location)
+ json_as_array = [[json.to_h]]
+
+ expect(json_as_array).to match_json_schema(schema)
+ end
+
+ it "fails against a schema that uses nested $refs" do
+ schema = create(:schema, :referencing_locations,
+ items: create(:schema, :referencing_locations))
+ json = build(:response, :invalid_location)
+ json_as_array = [[json.to_h]]
+
+ expect(json_as_array).not_to match_json_schema(schema)
+ end
+
  it "validates against a schema referencing with 'definitions'" do
  schema = create(:schema, :referencing_definitions)