Update eslintrc to allow smart '== null'

Author: Robert Zhu

.eslintrc

@@ -69,7 +69,7 @@
     "dot-location": [2, "property"],
     "dot-notation": 0,
     "eol-last": 2,
-    "eqeqeq": 2,
+    "eqeqeq": ["error", "smart"],
     "func-names": 0,
     "func-style": 0,
     "generator-star-spacing": [2, {"before": true, "after": false}],

src/type/__tests__/validation-test.js

@@ -1148,15 +1148,15 @@ describe('Type System: Object fields must have valid resolve values', () => {
 
   it('rejects an empty Object field resolver', () => {
     expect(() => schemaWithObjectWithFieldResolver({})).to.throw(
-      'BadResolver.badField field resolver must be function or null/undefined' +
-      ', but got: [object Object].'
+      'BadResolver.badField field resolver must be a function if provided, ' +
+      'but got: [object Object].'
     );
   });
 
   it('rejects a constant scalar value resolver', () => {
     expect(() => schemaWithObjectWithFieldResolver(0)).to.throw(
-      'BadResolver.badField field resolver must be function or null/undefined' +
-      ', but got: 0.'
+      'BadResolver.badField field resolver must be a function if provided, ' +
+      'but got: 0.'
     );
   });
 });

src/type/definition.js

@@ -508,8 +508,8 @@ function defineFieldMap<TSource, TContext>(
     );
     invariant(
       isValidResolver(field.resolve),
-      `${type.name}.${fieldName} field resolver must be function or null/` +
-      `undefined, but got: ${String(field.resolve)}.`
+      `${type.name}.${fieldName} field resolver must be a function if ` +
+      `provided, but got: ${String(field.resolve)}.`
     );
     const argsConfig = fieldConfig.args;
     if (!argsConfig) {
@@ -547,10 +547,7 @@ function isPlainObj(obj) {
 
 // If a resolver is defined, it must be a function.
 function isValidResolver(resolver: any): boolean {
-  if (resolver === null || resolver === undefined) {
-    return true;
-  }
-  return typeof resolver === 'function';
+  return (resolver == null || typeof resolver === 'function');
 }
 
 export type GraphQLObjectTypeConfig<TSource, TContext> = {