Improve descriptions support

Fix using kind with object injections. Support descriptions in
InputObject fields. Include descriptions in args introspection.

Based on PR #22 by @no1seman

Author: no1seman

graphql/execute.lua

@@ -260,6 +260,7 @@ local function getFieldEntry(objectType, object, fields, context)
 
   local arguments = util.map(fieldType.arguments or {}, function(argument, name)
     local supplied = argumentMap[name] and argumentMap[name].value
+    if argument.kind then argument = argument.kind end
     return util.coerceValue(supplied, argument, context.variables, {
       strict_non_null = true,
       defaultValues = defaultValues,

graphql/introspection.lua

@@ -7,7 +7,7 @@ local __Schema, __Directive, __DirectiveLocation, __Type, __Field, __InputValue,
 local function resolveArgs(field)
     local function transformArg(arg, name)
         if arg.__type then
-            return { kind = arg, name = name }
+            return { kind = arg, name = name, description = arg.description }
         elseif arg.name then
             return arg
         else

graphql/rules.lua

@@ -516,6 +516,7 @@ local function isVariableTypesValid(argument, argumentType, context,
     if hasDefault and variableType.__type ~= 'NonNull' then
       variableType = types.nonNull(variableType)
     end
+    if argumentType.kind then argumentType = argumentType.kind end
 
     if not isTypeSubTypeOf(variableType, argumentType, context) then
       return false, ('Variable "%s" type mismatch: the variable type "%s" ' ..

graphql/types.lua

@@ -224,6 +224,7 @@ function types.inputObject(config)
     fields[fieldName] = {
       name = fieldName,
       kind = field.kind,
+      description = field.description,
     }
   end
 

test/integration/graphql_test.lua

@@ -1509,3 +1509,82 @@ function g.test_specifiedBy_directive()
     t.assert_equals(data, { test_A = { url = "http://localhost", value = "1" } })
     t.assert_equals(errors, nil)
 end
+
+function g.test_descriptions()
+    local function callback(_, _)
+        return nil
+    end
+
+    local query_schema = {
+        ['test_query'] = {
+            kind = types.string.nonNull,
+            arguments = {
+                arg = types.string,
+                arg_described = {
+                    kind = types.object({
+                        name = 'test_object',
+                        fields = {
+                            object_arg_described = {
+                                kind = types.string,
+                                description = 'object argument'
+                            },
+                            object_arg = types.string,
+                        },
+                        kind = types.string,
+                    }),
+                    description = 'described query argument',
+                }
+            },
+            resolve = callback,
+            description = 'test query',
+        }
+    }
+
+    local mutation_schema = {
+        ['test_mutation'] = {
+            kind = types.string.nonNull,
+            arguments = {
+                mutation_arg = types.string,
+                mutation_arg_described = {
+                    kind = types.inputObject({
+                        name = 'test_input_object',
+                        fields = {
+                            input_object_arg_described = {
+                                kind = types.string,
+                                description = 'input object argument'
+                            },
+                            input_object_arg = types.string,
+                        },
+                        kind = types.string,
+                    }),
+                    description = 'described mutation argument',
+                },
+            },
+            resolve = callback,
+            description = 'test mutation',
+        }
+    }
+
+    local data, errors = check_request(introspection.query, query_schema, mutation_schema)
+    t.assert_equals(errors, nil)
+
+    local test_query = util.find_by_name(data.__schema.types, 'Query')
+    t.assert_equals(test_query.fields[1].description, 'test query')
+
+    local arg_described = util.find_by_name(test_query.fields[1].args, 'arg_described')
+    t.assert_equals(arg_described.description, 'described query argument')
+
+    local test_object = util.find_by_name(data.__schema.types, 'test_object')
+    local object_arg_described = util.find_by_name(test_object.fields, 'object_arg_described')
+    t.assert_equals(object_arg_described.description, 'object argument')
+
+    local test_mutation = util.find_by_name(data.__schema.types, 'Mutation')
+    t.assert_equals(test_mutation.fields[1].description, 'test mutation')
+
+    local mutation_arg_described = util.find_by_name(test_mutation.fields[1].args, 'mutation_arg_described')
+    t.assert_equals(mutation_arg_described.description, 'described mutation argument')
+
+    local test_input_object = util.find_by_name(data.__schema.types, 'test_input_object')
+    local input_object_arg_described = util.find_by_name(test_input_object.inputFields, 'input_object_arg_described')
+    t.assert_equals(input_object_arg_described.description, 'input object argument')
+end