From aa7208909971ced421250df966c8a3d69e98d35a Mon Sep 17 00:00:00 2001
From: Robert Zhu <robzhu@fb.com>
Date: Thu, 21 Apr 2016 16:15:45 -0400
Subject: [PATCH 1/2] Improve validation error message when field names
 conflict

---
 src/validation/rules/OverlappingFieldsCanBeMerged.js | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/src/validation/rules/OverlappingFieldsCanBeMerged.js b/src/validation/rules/OverlappingFieldsCanBeMerged.js
index 2c2c8edcab..a773229b4d 100644
--- a/src/validation/rules/OverlappingFieldsCanBeMerged.js
+++ b/src/validation/rules/OverlappingFieldsCanBeMerged.js
@@ -39,14 +39,16 @@ export function fieldsConflictMessage(
   responseName: string,
   reason: ConflictReasonMessage
 ): string {
-  return `Fields "${responseName}" conflict because ${reasonMessage(reason)}.`;
+  return `Fields "${responseName}" conflict because ${reasonMessage(reason)}` +
+    '. Use aliases on the fields to fetch both if this was intentional.';
 }
 
 function reasonMessage(reason: ConflictReasonMessage): string {
   if (Array.isArray(reason)) {
     return reason.map(([ responseName, subreason ]) =>
       `subfields "${responseName}" conflict because ${reasonMessage(subreason)}`
-    ).join(' and ');
+    ).join(' and ') +
+      '. Use aliases on the fields to fetch both if this was intentional.';
   }
   return reason;
 }

From 7d2f1916f110d985a8b4ae6ae8c6389f0cd09963 Mon Sep 17 00:00:00 2001
From: Robert Zhu <robzhu@fb.com>
Date: Mon, 25 Apr 2016 17:05:57 -0400
Subject: [PATCH 2/2] Remove extra hint and add unit test

---
 package.json                                        |  1 +
 .../__tests__/OverlappingFieldsCanBeMerged-test.js  | 13 +++++++++++++
 .../rules/OverlappingFieldsCanBeMerged.js           |  6 +++---
 3 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/package.json b/package.json
index c8d24cee72..b8f5c03e4b 100644
--- a/package.json
+++ b/package.json
@@ -61,6 +61,7 @@
     "babel-plugin-transform-runtime": "6.6.0",
     "babel-preset-es2015": "6.6.0",
     "chai": "3.5.0",
+    "chai-string": "1.2.0",
     "chai-subset": "1.2.2",
     "coveralls": "2.11.9",
     "eslint": "2.7.0",
diff --git a/src/validation/__tests__/OverlappingFieldsCanBeMerged-test.js b/src/validation/__tests__/OverlappingFieldsCanBeMerged-test.js
index 457a0dad05..65e329601e 100644
--- a/src/validation/__tests__/OverlappingFieldsCanBeMerged-test.js
+++ b/src/validation/__tests__/OverlappingFieldsCanBeMerged-test.js
@@ -7,6 +7,7 @@
  *  of patent rights can be found in the PATENTS file in the same directory.
  */
 
+import { expect } from 'chai';
 import { describe, it } from 'mocha';
 import {
   expectPassesRule,
@@ -28,7 +29,10 @@ import {
   GraphQLString,
   GraphQLID,
 } from '../../type';
+import chai from 'chai';
+import chaiString from 'chai-string';
 
+chai.use(chaiString);
 
 describe('Validate: Overlapping fields can be merged', () => {
 
@@ -753,6 +757,15 @@ describe('Validate: Overlapping fields can be merged', () => {
       `);
     });
 
+    it('error message contains hint for alias conflict', () => {
+      // The error template should end with a hint for the user to try using
+      // different aliases.
+      const error = fieldsConflictMessage('x', 'a and b are different fields');
+      const hint = 'Use different aliases on the fields to fetch both ' +
+                   'if this was intentional.';
+      expect(error).to.endsWith(hint);
+    });
+
   });
 
 });
diff --git a/src/validation/rules/OverlappingFieldsCanBeMerged.js b/src/validation/rules/OverlappingFieldsCanBeMerged.js
index a773229b4d..38c506ddca 100644
--- a/src/validation/rules/OverlappingFieldsCanBeMerged.js
+++ b/src/validation/rules/OverlappingFieldsCanBeMerged.js
@@ -40,15 +40,15 @@ export function fieldsConflictMessage(
   reason: ConflictReasonMessage
 ): string {
   return `Fields "${responseName}" conflict because ${reasonMessage(reason)}` +
-    '. Use aliases on the fields to fetch both if this was intentional.';
+    '. Use different aliases on the fields to fetch both if this was ' +
+    'intentional.';
 }
 
 function reasonMessage(reason: ConflictReasonMessage): string {
   if (Array.isArray(reason)) {
     return reason.map(([ responseName, subreason ]) =>
       `subfields "${responseName}" conflict because ${reasonMessage(subreason)}`
-    ).join(' and ') +
-      '. Use aliases on the fields to fetch both if this was intentional.';
+    ).join(' and ');
   }
   return reason;
 }