Add symbol option to insert_property_defaults

This allows default properties to be inserted using symbol keys.

I didn't think about this when adding symbol key support everywhere. I
don't love overloading `insert_property_defaults` like this, but it
seems slightly better than adding another option (or
`property_default_resolver: :symbol` or whatever).

Addresses: #166

README.md

@@ -212,7 +212,8 @@ JSONSchemer.schema(
   },
 
   # insert default property values during validation
-  # true/false
+  # string keys by default (use `:symbol` to insert symbol keys)
+  # true/false/:symbol
   # default: false
   insert_property_defaults: true,
 

lib/json_schemer/schema.rb

@@ -46,10 +46,13 @@ def original_instance(instance_location)
         false
       end
     end
+    SYMBOL_PROPERTY_DEFAULT_RESOLVER = proc do |instance, property, results_with_tree_validity|
+      DEFAULT_PROPERTY_DEFAULT_RESOLVER.call(instance, property.to_sym, results_with_tree_validity)
+    end
 
     attr_accessor :base_uri, :meta_schema, :keywords, :keyword_order
     attr_reader :value, :parent, :root, :parsed
-    attr_reader :vocabulary, :format, :formats, :content_encodings, :content_media_types, :custom_keywords, :before_property_validation, :after_property_validation, :insert_property_defaults, :property_default_resolver
+    attr_reader :vocabulary, :format, :formats, :content_encodings, :content_media_types, :custom_keywords, :before_property_validation, :after_property_validation, :insert_property_defaults
 
     def initialize(
       value,
@@ -67,7 +70,7 @@ def initialize(
       before_property_validation: DEFAULT_BEFORE_PROPERTY_VALIDATION,
       after_property_validation: DEFAULT_AFTER_PROPERTY_VALIDATION,
       insert_property_defaults: false,
-      property_default_resolver: DEFAULT_PROPERTY_DEFAULT_RESOLVER,
+      property_default_resolver: nil,
       ref_resolver: DEFAULT_REF_RESOLVER,
       regexp_resolver: 'ruby',
       output_format: 'classic',
@@ -401,6 +404,10 @@ def root_keyword_location
       @root_keyword_location ||= Location.root
     end
 
+    def property_default_resolver
+      @property_default_resolver ||= insert_property_defaults == :symbol ? SYMBOL_PROPERTY_DEFAULT_RESOLVER : DEFAULT_PROPERTY_DEFAULT_RESOLVER
+    end
+
     def ref_resolver
       @ref_resolver ||= @original_ref_resolver == 'net/http' ? CachedResolver.new(&NET_HTTP_REF_RESOLVER) : @original_ref_resolver
     end

test/hooks_test.rb

@@ -100,6 +100,28 @@ def test_it_inserts_defaults_in_symbol_keys
     assert_equal('x', instance.dig(:a, :b, 'c'))
   end
 
+  def test_it_can_insert_symbol_keys
+    schema = {
+      'properties' => {
+        'a' => {
+          'default' => 'x'
+        }
+      }
+    }
+
+    schemer = JSONSchemer.schema(schema, insert_property_defaults: true)
+    instance = {}
+    schemer.validate(instance)
+    refute(instance.key?(:a))
+    assert_equal('x', instance.fetch('a'))
+
+    schemer = JSONSchemer.schema(schema, insert_property_defaults: :symbol)
+    instance = {}
+    schemer.validate(instance)
+    refute(instance.key?('a'))
+    assert_equal('x', instance.fetch(:a))
+  end
+
   def test_it_does_not_fail_using_insert_defaults_when_no_properties_are_defined_by_schema
     schema = {
       '$comment' => 'Mostly empty schema'