Add Context#add_error

Allows errors to be added while returning value from resolver.

Author: josh

lib/graphql/query/context.rb

@@ -45,6 +45,21 @@ def [](key)
       def []=(key, value)
         @values[key] = value
       end
+
+      # Add error to current field resolution.
+      # @param error [GraphQL::ExecutionError] an execution error
+      # @return [void]
+      def add_error(error)
+        unless error.is_a?(ExecutionError)
+          raise TypeError, "expected error to be a ExecutionError, but was #{error.class}"
+        end
+
+        error.ast_node = irep_node.ast_node
+        error.path = irep_node.path
+        errors << error
+
+        nil
+      end
     end
   end
 end

spec/graphql/execution_error_spec.rb

@@ -44,6 +44,7 @@
         }
       }
       executionError
+      valueWithExecutionError
     }
 
     fragment similarCheeseFields on Cheese {
@@ -90,6 +91,7 @@
               ]
             },
             "executionError" => nil,
+            "valueWithExecutionError" => 0
           },
           "errors"=>[
             {
@@ -127,6 +129,11 @@
               "locations"=>[{"line"=>41, "column"=>7}],
               "path"=>["executionError"]
             },
+            {
+              "message"=>"Could not fetch latest value",
+              "locations"=>[{"line"=>42, "column"=>7}],
+              "path"=>["valueWithExecutionError"]
+            },
           ]
         }
       assert_equal(expected_result, result)

spec/graphql/introspection/schema_type_spec.rb

@@ -32,6 +32,7 @@
             {"name"=>"milk"},
             {"name"=>"root"},
             {"name"=>"searchDairy"},
+            {"name"=>"valueWithExecutionError"},
           ]
         },
         "mutationType"=> {

spec/support/dairy_app.rb

@@ -297,6 +297,14 @@ def self.create(type:, data:)
     resolve ->(t, a, c) { raise(GraphQL::ExecutionError, "There was an execution error") }
   end
 
+  field :valueWithExecutionError do
+    type !GraphQL::INT_TYPE
+    resolve ->(t, a, c) {
+      c.add_error(GraphQL::ExecutionError.new("Could not fetch latest value"))
+      return 0
+    }
+  end
+
   # To test possibly-null fields
   field :maybeNull, MaybeNullType do
     resolve ->(t, a, c) { OpenStruct.new(cheese: nil) }