return data and errors acc. to GraphQL spec #7.1.2

Author: no1seman

.gitignore

@@ -26,3 +26,5 @@ luacov.*.out*
 /node_modules
 /package-lock.json
 *.mo
+.history
+.vscode

graphql/execute.lua

@@ -301,30 +301,35 @@ local function getFieldEntry(objectType, object, fields, context)
   }
 
   local resolvedObject, err = (fieldType.resolve or defaultResolver)(object, arguments, info)
-  if err ~= nil then
+  if resolvedObject == nil and err ~= nil then
     error(err)
   end
 
   local subSelections = mergeSelectionSets(fields)
   return completeValue(fieldType.kind, resolvedObject, subSelections, context,
     {fieldName = fieldName}
-  )
+  ), err
 end
 
 evaluateSelections = function(objectType, object, selections, context)
   local result = {}
+  local errors
+  local err
   local fields = collectFields(objectType, selections, {}, {}, context)
   for _, field in ipairs(fields) do
     assert(result[field.name] == nil,
       'two selections into the one field: ' .. field.name)
-    result[field.name] = getFieldEntry(objectType, object, {field.selection},
+    result[field.name], err = getFieldEntry(objectType, object, {field.selection},
                                        context)
-
+    if err ~= nil then
+        errors = errors or {}
+        table.insert(errors, err)
+    end
     if result[field.name] == nil then
         result[field.name] = box.NULL
     end
   end
-  return result
+  return result, errors
 end
 
 local function execute(schema, tree, rootValue, variables, operationName)

test/integration/graphql_test.lua

@@ -1129,3 +1129,29 @@ function g.test_validation_non_null_argument_error()
             end
     )
 end
+
+function g.test_both_data_and_error_result()
+    local query = [[
+        { test(arg: "A") }
+    ]]
+
+    local function callback(_, args)
+        return args[1].value, {message = 'Simple error'}
+    end
+
+    local query_schema = {
+        ['test'] = {
+            kind = types.string.nonNull,
+            arguments = {
+                arg = types.string.nonNull,
+                arg2 = types.string,
+                arg3 = types.int,
+                arg4 = types.long,
+            },
+            resolve = callback,
+        }
+    }
+    local data, errors = check_request(query, query_schema)
+    t.assert_equals(data, {test = 'A'})
+    t.assert_equals(errors,  {{message = 'Simple error'}})
+end