Allow consistent permitting classes

bridgetown-core/lib/bridgetown-core/yaml_parser.rb

@@ -6,12 +6,23 @@ class YAMLParser
 
     class << self
       def load_file(filename, **kwargs)
-        kwargs = { permitted_classes: PERMITTED_CLASSES }.merge(kwargs)
-        YAML.safe_load_file(filename, **kwargs)
+        YAML.safe_load_file filename, **merge_permitted_classes(kwargs)
       end
 
-      def load(yaml)
-        YAML.safe_load yaml, permitted_classes: PERMITTED_CLASSES
+      def load(yaml, **kwargs)
+        YAML.safe_load yaml, **merge_permitted_classes(kwargs)
+      end
+
+      private
+
+      def merge_permitted_classes(kwargs)
+        if kwargs.key?(:permitted_classes)
+          kwargs[:permitted_classes] |= PERMITTED_CLASSES
+        else
+          kwargs[:permitted_classes] = PERMITTED_CLASSES
+        end
+
+        kwargs
       end
     end
   end

bridgetown-core/test/fixtures/extra_yaml.yml

@@ -0,0 +1,6 @@
+---
+date: 2020-05-14
+time: 2019-07-14 19:22:00 +0100
+rb: !ruby/string:Rb |
+  21 * 2
+symbol: :symbol

bridgetown-core/test/test_yaml_parser.rb

@@ -34,6 +34,21 @@ def initialize
       assert_equal Rb, parsed_yaml["rb"].class
     end
 
+    should "allows passing other permitted classes" do
+      parsed_yaml = Bridgetown::YAMLParser.load(<<~YAML, permitted_classes: [Symbol])
+        date: 2020-05-14
+        time: 2019-07-14 19:22:00 +0100
+        rb: !ruby/string:Rb |
+          21 * 2
+        symbol: :symbol
+      YAML
+
+      assert_equal Date, parsed_yaml["date"].class
+      assert_equal Time, parsed_yaml["time"].class
+      assert_equal Rb, parsed_yaml["rb"].class
+      assert_equal :symbol, parsed_yaml["symbol"]
+    end
+
     should "error when trying to parse types not on the allowlist" do
       assert_raises(Psych::DisallowedClass) do
         Bridgetown::YAMLParser.load(CustomYAMLSerializable.new.to_yaml)
@@ -51,6 +66,16 @@ def initialize
       assert_equal Rb, parsed_yaml["rb"].class
     end
 
+    should "allows passing other permitted classes" do
+      yaml_file = test_dir("fixtures", "extra_yaml.yml")
+      parsed_yaml = Bridgetown::YAMLParser.load_file(yaml_file, permitted_classes: [Symbol])
+
+      assert_equal Date, parsed_yaml["date"].class
+      assert_equal Time, parsed_yaml["time"].class
+      assert_equal Rb, parsed_yaml["rb"].class
+      assert_equal :symbol, parsed_yaml["symbol"]
+    end
+
     should "error when trying to parse types not on the allowlist" do
       yaml_file = test_dir("fixtures", "disallowed_yaml.yml")