Support Schema#ref in subschemas

`resolve_ref` needs to be called on the root schema because that's where
all the `resources` are stored.

The behavior here is kind of confusing because the ref is resolved just
like the `$ref` keyword would be in the schema, so it's dependent on the
schema's base URI. That means for a subschema `ref('#')` doesn't
necessarily resolve to itself (ie, if the subschema doesn't have `$id`).

CHANGELOG.md

@@ -5,6 +5,7 @@
 ### Bug Fixes
 
 - Require discriminator `propertyName` property
+- Support `Schema#ref` in subschemas
 
 [2.1.0]: https://github.com/davishmcclurg/json_schemer/releases/tag/v2.1.0
 

lib/json_schemer/schema.rb

@@ -113,7 +113,7 @@ def validate_schema
     end
 
     def ref(value)
-      resolve_ref(URI.join(base_uri, value))
+      root.resolve_ref(URI.join(base_uri, value))
     end
 
     def validate_instance(instance, instance_location, keyword_location, context)

test/json_schemer_test.rb

@@ -380,6 +380,12 @@ def test_schema_ref
       'type' => 'integer',
       '$defs' => {
         'foo' => {
+          '$id' => 'subschemer',
+          '$defs' => {
+            'bar' => {
+              'required' => ['z']
+            }
+          },
           'type' => 'object',
           'required' => ['x', 'y'],
           'properties' => {
@@ -401,10 +407,20 @@ def test_schema_ref
 
     refute(subschemer.valid?(1))
     assert_equal(
-      [["/x", "/$defs/foo/properties/x", "string"], ["", "/$defs/foo", "required"]],
+      [['/x', '/$defs/foo/properties/x', 'string'], ['', '/$defs/foo', 'required']],
       subschemer.validate({ 'x' => 1 }).map { |error| error.values_at('data_pointer', 'schema_pointer', 'type') }
     )
     assert(subschemer.valid?({ 'x' => '1', 'y' => 1 }))
+
+    subsubschemer = subschemer.ref('#/$defs/bar')
+    refute(subsubschemer.valid?({ 'x' => 1 }))
+    assert_equal(
+      [['', '/$defs/foo/$defs/bar', 'required']],
+      subsubschemer.validate({ 'x' => 1 }).map { |error| error.values_at('data_pointer', 'schema_pointer', 'type') }
+    )
+
+    assert_equal(subschemer, subschemer.ref('#'))
+    assert_equal(subschemer, subsubschemer.ref('#'))
   end
 
   def test_published_meta_schemas