From dce7d6e69034a1338a7ee61c980ad74218be1f22 Mon Sep 17 00:00:00 2001
From: Ivan Goncharov <ivan.goncharov.ua@gmail.com>
Date: Fri, 27 Sep 2019 14:36:00 +0300
Subject: [PATCH] findBreakingChanges: better message for removing standard
 scalar

Fixes #2197
---
 .../__tests__/findBreakingChanges-test.js     | 33 +++++++++++++++++--
 src/utilities/findBreakingChanges.js          |  5 ++-
 2 files changed, 34 insertions(+), 4 deletions(-)

diff --git a/src/utilities/__tests__/findBreakingChanges-test.js b/src/utilities/__tests__/findBreakingChanges-test.js
index ddb0cf9c1a..420ee42b68 100644
--- a/src/utilities/__tests__/findBreakingChanges-test.js
+++ b/src/utilities/__tests__/findBreakingChanges-test.js
@@ -37,6 +37,32 @@ describe('findBreakingChanges', () => {
     expect(findBreakingChanges(oldSchema, oldSchema)).to.deep.equal([]);
   });
 
+  it('should detect if a standard scalar was removed', () => {
+    const oldSchema = buildSchema(`
+      type Query {
+        foo: Float
+      }
+    `);
+
+    const newSchema = buildSchema(`
+      type Query {
+        foo: String
+      }
+    `);
+    expect(findBreakingChanges(oldSchema, newSchema)).to.deep.equal([
+      {
+        type: BreakingChangeType.TYPE_REMOVED,
+        description:
+          'Standard scalar Float was removed because it is not referenced anymore.',
+      },
+      {
+        type: BreakingChangeType.FIELD_CHANGED_KIND,
+        description: 'Query.foo changed type from Float to String.',
+      },
+    ]);
+    expect(findBreakingChanges(oldSchema, oldSchema)).to.deep.equal([]);
+  });
+
   it('should detect if a type changed its type', () => {
     const oldSchema = buildSchema(`
       scalar TypeWasScalarBecomesEnum
@@ -601,7 +627,7 @@ describe('findBreakingChanges', () => {
       directive @DirectiveName on FIELD_DEFINITION | QUERY
 
       type ArgThatChanges {
-        field1(id: Int): String
+        field1(id: Float): String
       }
 
       enum EnumTypeThatLosesAValue {
@@ -660,7 +686,8 @@ describe('findBreakingChanges', () => {
     expect(findBreakingChanges(oldSchema, newSchema)).to.deep.equal([
       {
         type: BreakingChangeType.TYPE_REMOVED,
-        description: 'Int was removed.',
+        description:
+          'Standard scalar Float was removed because it is not referenced anymore.',
       },
       {
         type: BreakingChangeType.TYPE_REMOVED,
@@ -669,7 +696,7 @@ describe('findBreakingChanges', () => {
       {
         type: BreakingChangeType.ARG_CHANGED_KIND,
         description:
-          'ArgThatChanges.field1 arg id has changed type from Int to String.',
+          'ArgThatChanges.field1 arg id has changed type from Float to String.',
       },
       {
         type: BreakingChangeType.VALUE_REMOVED_FROM_ENUM,
diff --git a/src/utilities/findBreakingChanges.js b/src/utilities/findBreakingChanges.js
index d53b107dd7..98863f8402 100644
--- a/src/utilities/findBreakingChanges.js
+++ b/src/utilities/findBreakingChanges.js
@@ -10,6 +10,7 @@ import { print } from '../language/printer';
 import { visit } from '../language/visitor';
 
 import { type GraphQLSchema } from '../type/schema';
+import { isSpecifiedScalarType } from '../type/scalars';
 import {
   type GraphQLField,
   type GraphQLType,
@@ -176,7 +177,9 @@ function findTypeChanges(
   for (const oldType of typesDiff.removed) {
     schemaChanges.push({
       type: BreakingChangeType.TYPE_REMOVED,
-      description: `${oldType.name} was removed.`,
+      description: isSpecifiedScalarType(oldType)
+        ? `Standard scalar ${oldType.name} was removed because it is not referenced anymore.`
+        : `${oldType.name} was removed.`,
     });
   }