Fix derive not returning (needsSubscription issues) (#658)

Fix derive not subscribing (needsSubscription issues)

packages/api/src/Base.ts

@@ -480,7 +480,19 @@ export default abstract class ApiBase<CodecResult, SubscriptionResult> implement
       const sectionName = _sectionName as keyof DeriveInterface;
 
       result[sectionName] = Object.keys(derive[sectionName]).reduce((section, methodName) => {
-        const method = (...params: any[]) => onCall((derive[sectionName] as any)[methodName], params);
+        // FIXME The callback extraction we do way too much - de-dupe
+        const method = (...args: Array<any>) => {
+          let callback: CodecCallback | undefined;
+          let params = args;
+
+          if (args.length && isFunction(args[args.length - 1])) {
+            callback = args[args.length - 1];
+            params = args.slice(0, args.length - 1);
+          }
+
+          return onCall((derive[sectionName] as any)[methodName], params, callback, !!callback);
+        };
+
         section[methodName] = method;
 
         return section;

packages/api/test/e2e/promise-queries.spec.js

@@ -13,7 +13,10 @@ describe.skip('e2e queries', () => {
   let api;
 
   beforeEach(async (done) => {
-    api = await Api.create();
+    if (!api) {
+      api = await Api.create();
+    }
+
     jest.setTimeout(30000);
     done();
   });
@@ -44,6 +47,14 @@ describe.skip('e2e queries', () => {
     });
   });
 
+  it('subscribes to derive', (done) => {
+    api.derive.chain.subscribeNewHead((header) => {
+      expect(header.blockNumber.isZero()).toBe(false);
+
+      done();
+    });
+  });
+
   it('subscribes to queries', (done) => {
     api.query.system.accountNonce(keyring.ferdie.address(), (nonce) => {
       expect(nonce instanceof BN).toBe(true);