Validate behavior during execution

lib/graphql/static_validation/literal_validator.rb

@@ -108,6 +108,10 @@ def required_input_fields_are_present(type, ast_node)
             arg_type = @warden.get_argument(type, name).type
             recursively_validate(GraphQL::Language::Nodes::NullValue.new(name: name), arg_type)
           end
+
+          if type.one_of? && ast_node.arguments.size != 1
+            results << Query::InputValidationResult.from_problem("`#{type.graphql_name}` is a OneOf type, so only one argument may be given (instead of #{ast_node.arguments.size})")
+          end
           merge_results(results)
         end
       end

lib/graphql/static_validation/rules/variable_default_values_are_correctly_typed.rb

@@ -23,7 +23,7 @@ def on_variable_definition(node, parent)
                 problems = validation_result.problems
                 first_problem = problems && problems.first
                 if first_problem
-                  error_message = first_problem["message"]
+                  error_message = first_problem["explanation"]
                 end
 
                 error_message ||= "Default value for $#{node.name} doesn't match type #{type.to_type_signature}"

spec/graphql/schema/directive/one_of_spec.rb

@@ -33,8 +33,8 @@ def one_of_field(one_of_arg:)
       graphql_name "OneOfInputObject"
       directive GraphQL::Schema::Directive::OneOf
 
-      argument :int, GraphQL::Types::Int
-      argument :string, GraphQL::Types::String
+      argument :int, GraphQL::Types::Int, required: false
+      argument :string, GraphQL::Types::String, required: false
     end
   end
 
@@ -75,4 +75,86 @@ def one_of_field(one_of_arg:)
       end
     end
   end
+
+  describe "execution" do
+    let(:query) do
+      <<~GRAPHQL
+        query TestQuery($oneOfInputObject: OneOfInputObject!) {
+          oneOfField(oneOfArg: $oneOfInputObject) {
+            string
+            int
+          }
+        }
+      GRAPHQL
+    end
+
+    it "accepts a default value with exactly one non-null key" do
+      query = <<~GRAPHQL
+        query TestQuery($oneOfInputObject: OneOfInputObject = { string: "default" }) {
+          oneOfField(oneOfArg: $oneOfInputObject) {
+            string
+            int
+          }
+        }
+      GRAPHQL
+
+      result = schema.execute(query)
+
+      assert_equal({ "string" => "default", "int" => nil }, result["data"]["oneOfField"])
+    end
+
+    it "rejects a default value with multiple non-null keys" do
+      query = <<~GRAPHQL
+        query TestQuery($oneOfInputObject: OneOfInputObject = { string: "default", int: 2 }) {
+          oneOfField(oneOfArg: $oneOfInputObject) {
+            string
+            int
+          }
+        }
+      GRAPHQL
+
+      result = schema.execute(query)
+
+      expected_errors = ["`OneOfInputObject` is a OneOf type, so only one argument may be given (instead of 2)"]
+      assert_equal(expected_errors, result["errors"].map { |e| e["message"] })
+    end
+
+    it "rejects a default value with multiple nullable keys" do
+      query = <<~GRAPHQL
+        query TestQuery($oneOfInputObject: OneOfInputObject = { string: "default", int: null }) {
+          oneOfField(oneOfArg: $oneOfInputObject) {
+            string
+            int
+          }
+        }
+      GRAPHQL
+
+      result = schema.execute(query)
+
+      expected_errors = ["`OneOfInputObject` is a OneOf type, so only one argument may be given (instead of 2)"]
+      assert_equal(expected_errors, result["errors"].map { |e| e["message"] })
+    end
+
+    it "accepts a variable with exactly one non-null key" do
+      string_result = schema.execute(query, variables: { oneOfInputObject: { string: "abc" } })
+      int_result = schema.execute(query, variables: { oneOfInputObject: { int: 2 } })
+
+      assert_equal({ "string" => "abc", "int" => nil }, string_result["data"]["oneOfField"])
+      assert_equal({ "string" => nil, "int" => 2 }, int_result["data"]["oneOfField"])
+    end
+
+    it "rejects a variable with exactly one null key" do
+      result = schema.execute(query, variables: { oneOfInputObject: { string: nil } })
+
+      expected_errors = ["'OneOfInputObject' requires exactly one argument, but 'string' was `null`."]
+      assert_equal(expected_errors, result["errors"].map { |e| e["extensions"]["problems"].map { |pr| pr["explanation"] } }.flatten)
+    end
+
+    it "rejects a variable with multiple non-null keys" do
+      result = schema.execute(query, variables: { oneOfInputObject: { string: "abc", int: 2 } })
+
+      expected_errors = ["'OneOfInputObject' requires exactly one argument, but 2 were provided."]
+      assert_equal(expected_errors, result["errors"].map { |e| e["extensions"]["problems"].map { |pr| pr["explanation"] } }.flatten)
+    end
+  end
 end

spec/graphql/schema/warden_spec.rb

@@ -825,7 +825,7 @@ class Query < GraphQL::Schema::Object
       query getPhonemes($manners: [Manner!] = [STOP, TRILL]){ phonemes(manners: $manners) { symbol } }
       |
       res = MaskHelpers.query_with_mask(query_string, mask)
-      expected_errors = ["Default value for $manners doesn't match type [Manner!]"]
+      expected_errors = ["Expected \"TRILL\" to be one of: STOP, AFFRICATE, FRICATIVE, APPROXIMANT, VOWEL"]
       assert_equal expected_errors, error_messages(res)
     end
 

spec/graphql/static_validation/rules/variable_default_values_are_correctly_typed_spec.rb

@@ -25,13 +25,13 @@
   it "finds default values that don't match their types" do
     expected = [
       {
-        "message"=>"Default value for $badInt doesn't match type Int",
+        "message"=>"Could not coerce value \"abc\" to Int",
         "locations"=>[{"line"=>5, "column"=>7}],
         "path"=>["query getCheese"],
         "extensions"=>{"code"=>"defaultValueInvalidType", "variableName"=>"badInt", "typeName"=>"Int"}
       },
       {
-        "message"=>"Default value for $badInput doesn't match type DairyProductInput",
+        "message"=>"Could not coerce value true to Float",
         "locations"=>[{"line"=>7, "column"=>7}],
         "path"=>["query getCheese"],
         "extensions"=>{"code"=>"defaultValueInvalidType", "variableName"=>"badInput", "typeName"=>"DairyProductInput"}