GraphQLArgument: make 'description' undefined by default (#2132)

Author: IvanGoncharov

Diff for: src/type/__tests__/definition-test.js

@@ -243,7 +243,7 @@ describe('Type System: Objects', () => {
         args: [
           {
             name: 'arg',
-            description: null,
+            description: undefined,
             type: ScalarType,
             defaultValue: undefined,
             extensions: undefined,

Diff for: src/type/__tests__/directive-test.js

@@ -36,15 +36,15 @@ describe('Type System: Directive', () => {
       args: [
         {
           name: 'foo',
-          description: null,
+          description: undefined,
           type: GraphQLString,
           defaultValue: undefined,
           extensions: undefined,
           astNode: undefined,
         },
         {
           name: 'bar',
-          description: null,
+          description: undefined,
           type: GraphQLInt,
           defaultValue: undefined,
           extensions: undefined,

Diff for: src/type/definition.js

@@ -783,7 +783,7 @@ function defineFieldMap<TSource, TContext>(
 
     const args = objectEntries(argsConfig).map(([argName, arg]) => ({
       name: argName,
-      description: arg.description === undefined ? null : arg.description,
+      description: arg.description,
       type: arg.type,
       defaultValue: arg.defaultValue,
       extensions: arg.extensions && toObjMap(arg.extensions),

Diff for: src/type/directives.js

@@ -83,7 +83,7 @@ export class GraphQLDirective {
 
     this.args = objectEntries(args).map(([argName, arg]) => ({
       name: argName,
-      description: arg.description === undefined ? null : arg.description,
+      description: arg.description,
       type: arg.type,
       defaultValue: arg.defaultValue,
       extensions: arg.extensions,