Expand references of DocuemntStore schemas

This is a fix for #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

@@ -34,7 +34,8 @@ def build_and_populate_document_store
       Dir.glob("#{JsonMatchers.schema_root}/**/*.json").
         map { |path| Pathname.new(path) }.
         map { |schema_path| Parser.new(schema_path).parse }.
-        each { |schema| document_store.add_schema(schema) }
+        map { |schema| document_store.add_schema(schema) }.
+        each { |schema| schema.expand_references!(store: document_store) }
 
       document_store
     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 +202,26 @@
     expect(json_as_array).not_to match_json_schema(schema)
   end
 
+  it "validates against a schema that uses nested $refs" do
+    items = create(:schema, :referencing_locations)
+    schema = create(:schema, :referencing_locations, items: items)
+
+    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
+    items = create(:schema, :referencing_locations)
+    schema = create(:schema, :referencing_locations, items: items)
+
+    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)
 

test/json_matchers/minitest/assertions_test.rb

@@ -171,6 +171,27 @@ class AssertResponseMatchesSchemaTest < JsonMatchers::TestCase
     refute_matches_json_schema(json_as_array, schema)
   end
 
+  test "validates against a schema that uses nested $refs" do
+    items = create(:schema, :referencing_locations)
+    schema = create(:schema, :referencing_locations, items: items)
+
+    json = build(:response, :location)
+    json_as_array = [[json.to_h]]
+
+    assert_matches_json_schema(json_as_array, schema)
+  end
+
+  test "fails against a schema that uses nested $refs" do
+    items = create(:schema, :referencing_locations)
+    schema = create(:schema, :referencing_locations, items: items)
+
+    json = build(:response, :invalid_location)
+    json_as_array = [[json.to_h]]
+
+    refute_matches_json_schema(json_as_array, schema)
+  end
+
+
   test "validates against a schema referencing with 'definitions'" do
     schema = create(:schema, :referencing_definitions)