Remove Promise chain, fix formatting test subscription (#1218)

packages/rpc-core/src/formatting.spec.ts

@@ -42,7 +42,7 @@ function formattingTests (version: string, storage: Storage, encodedValues: [str
               : null
           )
         ),
-        subscribe: jest.fn((type, method, params, cb): void => {
+        subscribe: jest.fn((type, method, params, cb): Promise<void> => {
           if (params[0][0] === CONTRACT_KEY) {
             // this emulates https://github.com/polkadot-js/api/issues/1051
             cb(null, {
@@ -69,6 +69,8 @@ function formattingTests (version: string, storage: Storage, encodedValues: [str
               ]
             });
           }
+
+          return Promise.resolve();
         })
       };
 

packages/rpc-core/src/index.ts

@@ -198,12 +198,9 @@ export default class Rpc implements RpcInterface {
             observer.next(this.formatOutput(method, params, result));
           };
 
-          // FIXME This is a work-around, provider.subscribe _should_ always return,
-          // however in some cases `this.provider.subscribe.catch` yields ".catch of
-          // undefined", so here we flatten via Promise.reolve (which doe sfollow)
-          subscriptionPromise = Promise.resolve(
-            this.provider.subscribe(subType, subName, paramsJson, update)
-          ).catch(errorHandler);
+          subscriptionPromise = this.provider
+            .subscribe(subType, subName, paramsJson, update)
+            .catch(errorHandler);
         } catch (error) {
           errorHandler(error);
         }