Handle raised ExecutionErrors from prepare when calculating complexity

lib/graphql/schema/field.rb

@@ -496,7 +496,13 @@ def calculate_complexity(query:, nodes:, child_complexity:)
           case defined_complexity
           when Proc
             arguments = query.arguments_for(nodes.first, self)
-            defined_complexity.call(query.context, arguments.keyword_arguments, child_complexity)
+            if arguments.is_a?(GraphQL::ExecutionError)
+              return child_complexity
+            elsif arguments.respond_to?(:keyword_arguments)
+              arguments = arguments.keyword_arguments
+            end
+
+            defined_complexity.call(query.context, arguments, child_complexity)
           when Numeric
             defined_complexity + child_complexity
           else

spec/graphql/analysis/ast/query_complexity_spec.rb

@@ -8,7 +8,8 @@
     GraphQL::Analysis::AST.analyze_multiplex(multiplex, [GraphQL::Analysis::AST::QueryComplexity])
   }
   let(:variables) { {} }
-  let(:query) { GraphQL::Query.new(schema, query_string, variables: variables) }
+  let(:query_context) { {} }
+  let(:query) { GraphQL::Query.new(schema, query_string, context: query_context, variables: variables) }
   let(:multiplex) {
     GraphQL::Execution::Multiplex.new(
       schema: schema,
@@ -377,10 +378,20 @@ class DoubleComplexity < GraphQL::Schema::Object
 
       class Query < GraphQL::Schema::Object
         field :complexity, SingleComplexity do
-          argument :int_value, Int, required: false
+          argument :int_value, Int, required: false, prepare: ->(val, ctx) {
+            if ctx[:raise_prepare_error]
+              raise GraphQL::ExecutionError, "Boom"
+            else
+              val
+            end
+          }
           complexity ->(ctx, args, child_complexity) { args[:int_value] + child_complexity }
         end
 
+        def complexity(int_value:)
+          { value: int_value }
+        end
+
         field :inner_complexity, ComplexityInterface do
           argument :value, Int, required: false
         end
@@ -390,7 +401,7 @@ class Query < GraphQL::Schema::Object
       orphan_types(DoubleComplexity)
     end
 
-    let(:query) { GraphQL::Query.new(complexity_schema, query_string) }
+    let(:query) { GraphQL::Query.new(complexity_schema, query_string, context: query_context) }
     let(:complexity_schema) { CustomComplexitySchema }
     let(:query_string) {%|
       {
@@ -426,6 +437,18 @@ class Query < GraphQL::Schema::Object
         assert_equal 5, complexity
       end
     end
+
+    describe "when prepare raises an error" do
+      let(:query_string) { "{ complexity(intValue: 3) { value } }"}
+      let(:query_context) { { raise_prepare_error: true } }
+
+      it "handles it nicely" do
+        result = query.result
+        assert_equal ["Boom"], result["errors"].map { |e| e["message"] }
+        complexity = reduce_result.first
+        assert_equal 0.1, complexity
+      end
+    end
   end
 
   describe "custom complexities by complexity_for(...)" do