Patched: Issue apollographql#110 (apollographql#163)

* fixed shema forward() null error

* Avoid creating a new Observable

* Changelog update

Changelog.md

@@ -4,6 +4,9 @@
 
 - Integrate OneGraph's GraphiQL Explorer.  <br/>
   [@sgrove](https://github.com/sgrove) in [#199](https://github.com/apollographql/apollo-client-devtools/pull/199)
+- Make sure devtools can be used when the transport layer is websockets
+  only.  <br/>
+  [@kamerontanseli](https://github.com/kamerontanseli) in [#163](https://github.com/apollographql/apollo-client-devtools/pull/163) 
 
 ## 2.2.1
 

src/backend/links.js

@@ -15,15 +15,19 @@ import { buildSchemasFromTypeDefs } from "./typeDefs";
 const apolloClientSchema = {
   directives: "directive @connection(key: String!, filter: [String]) on FIELD",
 };
+
 const schemaLink = () =>
   new ApolloLink((operation, forward) => {
-    return forward(operation).map(result => {
-      let { schemas = [] } = operation.getContext();
-      result.extensions = Object.assign({}, result.extensions, {
-        schemas: schemas.concat([apolloClientSchema]),
-      });
-      return result;
-    });
+    const obs = forward(operation);
+    return obs.map
+      ? obs.map(result => {
+          let { schemas = [] } = operation.getContext();
+          result.extensions = Object.assign({}, result.extensions, {
+            schemas: schemas.concat([apolloClientSchema]),
+          });
+          return result;
+        })
+      : obs;
   });
 
 // Forward all "errors" to next with a good shape for graphiql