use getDescription from graphql package

.travis.yml

@@ -20,5 +20,4 @@ script:
 sudo: false
 
 env:
-  - GRAPHQL_VERSION='^0.12'
   - GRAPHQL_VERSION='^0.13'

CHANGELOG.md

@@ -1,5 +1,7 @@
 # Change log
 
+* Use `getDescription` from `graphql-js` package [PR #672](https://github.com/apollographql/graphql-tools/pull/672)
+
 ### v3.0.5
 
 * Update apollo-link to 1.2.2 [#785](https://github.com/apollographql/graphql-tools/pull/785)
@@ -18,7 +20,6 @@
   [Issue #753](https://github.com/apollographql/graphql-tools/issues/753)
   [PR #806](https://github.com/apollographql/graphql-tools/pull/806)
 
-
 ### v3.0.2
 
 * Fixed duplicate fragments getting added during transform in `FilterToSchema` [#778](https://github.com/apollographql/graphql-tools/pull/778)

package.json

@@ -55,11 +55,11 @@
     "uuid": "^3.1.0"
   },
   "peerDependencies": {
-    "graphql": "^0.12.0 || ^0.13.0"
+    "graphql": "^0.13.0"
   },
   "devDependencies": {
     "@types/chai": "4.0.10",
-    "@types/graphql": "0.11.7",
+    "@types/graphql": "0.12.5",
     "@types/dateformat": "^1.0.1",
     "@types/mocha": "^2.2.44",
     "@types/node": "^8.0.47",

src/generate/extractExtensionDefinitions.ts

@@ -1,16 +1,11 @@
 import { DocumentNode, DefinitionNode } from 'graphql';
 
-// This was changed in graphql@0.12
-// See https://github.com/apollographql/graphql-tools/pull/541
-// TODO fix types https://github.com/apollographql/graphql-tools/issues/542
-const oldTypeExtensionDefinitionKind = 'TypeExtensionDefinition';
 const newExtensionDefinitionKind = 'ObjectTypeExtension';
 const interfaceExtensionDefinitionKind = 'InterfaceTypeExtension';
 
 export default function extractExtensionDefinitions(ast: DocumentNode) {
   const extensionDefs = ast.definitions.filter(
     (def: DefinitionNode) =>
-      def.kind === oldTypeExtensionDefinitionKind ||
       (def.kind as any) === newExtensionDefinitionKind ||
       (def.kind as any) === interfaceExtensionDefinitionKind,
   );