fix(subscribe): allow interop with Monio and other libraries that patch function bind

* fix(subscribe): allows functions where bind has been patched to be weird

Apparently, code exists in the wild that will patch function bind to do something other than return a function that will execute the function instance, so we cannot rely on bind.

Resolves #6783

* refactor: Alternative bind approach

* chore: update side-effects golden files.

* chore: Add comment about why bind is captured

* chore: update side-effect files again

Author: benlesh

integration/side-effects/snapshots/esm/ajax.js

@@ -1 +1 @@
-
+const _bind = Function.prototype.bind;

integration/side-effects/snapshots/esm/fetch.js

@@ -1 +1,3 @@
 import "tslib";
+
+const _bind = Function.prototype.bind;

integration/side-effects/snapshots/esm/index.js

@@ -1,5 +1,7 @@
 import "tslib";
 
+const _bind = Function.prototype.bind;
+
 var NotificationKind;
 
 (function(NotificationKind) {

integration/side-effects/snapshots/esm/operators.js

@@ -1,5 +1,7 @@
 import "tslib";
 
+const _bind = Function.prototype.bind;
+
 var NotificationKind;
 
 (function(NotificationKind) {

integration/side-effects/snapshots/esm/testing.js

@@ -1,5 +1,7 @@
 import "tslib";
 
+const _bind = Function.prototype.bind;
+
 var NotificationKind;
 
 (function(NotificationKind) {

integration/side-effects/snapshots/esm/websocket.js

@@ -1 +1 @@
-
+const _bind = Function.prototype.bind;

integration/side-effects/snapshots/esm5/ajax.js

@@ -1 +1,3 @@
 import "tslib";
+
+var _bind = Function.prototype.bind;

integration/side-effects/snapshots/esm5/fetch.js

@@ -1 +1,3 @@
 import "tslib";
+
+var _bind = Function.prototype.bind;

integration/side-effects/snapshots/esm5/index.js

@@ -1,5 +1,7 @@
 import "tslib";
 
+var _bind = Function.prototype.bind;
+
 var NotificationKind;
 
 (function(NotificationKind) {

integration/side-effects/snapshots/esm5/operators.js

@@ -1,5 +1,7 @@
 import "tslib";
 
+var _bind = Function.prototype.bind;
+
 var NotificationKind;
 
 (function(NotificationKind) {

integration/side-effects/snapshots/esm5/testing.js

@@ -1,5 +1,7 @@
 import "tslib";
 
+var _bind = Function.prototype.bind;
+
 var NotificationKind;
 
 (function(NotificationKind) {

integration/side-effects/snapshots/esm5/websocket.js

@@ -1 +1,3 @@
 import "tslib";
+
+var _bind = Function.prototype.bind;

spec/Observable-spec.ts

@@ -191,6 +191,34 @@ describe('Observable', () => {
   });
 
   describe('subscribe', () => {
+    it('should work with handlers with hacked bind methods', () => {
+      const source = of('Hi');
+      const results: any[] = [];
+      const next = function (value: string) {
+        results.push(value);
+      }
+      next.bind = () => { /* lol */};
+      
+      const complete = function () {
+        results.push('done');
+      }
+      complete.bind = () => { /* lol */};
+
+      source.subscribe({ next, complete });
+      expect(results).to.deep.equal(['Hi', 'done']);
+    });
+
+    it('should work with handlers with hacked bind methods, in the error case', () => {
+      const source = throwError(() => 'an error');
+      const results: any[] = [];
+      const error = function (value: string) {
+        results.push(value);
+      }
+
+      source.subscribe({ error });
+      expect(results).to.deep.equal(['an error']);
+    });
+
     it('should be synchronous', () => {
       let subscribed = false;
       let nexted: string;

src/internal/Subscriber.ts

@@ -136,6 +136,17 @@ export class Subscriber<T> extends Subscription implements Observer<T> {
   }
 }
 
+/**
+ * This bind is captured here because we want to be able to have
+ * compatibility with monoid libraries that tend to use a method named
+ * `bind`. In particular, a library called Monio requires this.
+ */
+const _bind = Function.prototype.bind;
+
+function bind<Fn extends (...args: any[]) => any>(fn: Fn, thisArg: any): Fn {
+  return _bind.call(fn, thisArg);
+}
+
 export class SafeSubscriber<T> extends Subscriber<T> {
   constructor(
     observerOrNext?: Partial<Observer<T>> | ((value: T) => void) | null,
@@ -166,9 +177,9 @@ export class SafeSubscriber<T> extends Subscriber<T> {
       } else {
         context = observerOrNext;
       }
-      next = next?.bind(context);
-      error = error?.bind(context);
-      complete = complete?.bind(context);
+      next = next && bind(next, context);
+      error = error && bind(error, context);
+      complete = complete && bind(complete, context);
     }
 
     // Once we set the destination, the superclass `Subscriber` will