Gracefully handle multiple contexts for secondary DOM World (#1102)

* Gracefully handle multiple contexts for secondary DOM World

* Fix HasContext property

Author: kblok

lib/PuppeteerSharp.Tests/PuppeteerTests/PuppeteerConnectTests.cs

@@ -95,6 +95,31 @@ public async Task ShouldBeAbleToReconnectToADisconnectedBrowser()
             }
         }
 
+        [Fact]
+        public async Task ShouldBeAbleToConnectToTheSamePageSimultaneously()
+        {
+            var browserOne = await Puppeteer.LaunchAsync(new LaunchOptions());
+            var browserTwo = await Puppeteer.ConnectAsync(new ConnectOptions
+            {
+                BrowserWSEndpoint = browserOne.WebSocketEndpoint
+            });
+            var tcs = new TaskCompletionSource<Page>();
+            async void TargetCreated(object sender, TargetChangedArgs e)
+            {
+                tcs.TrySetResult(await e.Target.PageAsync());
+                browserOne.TargetCreated -= TargetCreated;
+            }
+            browserOne.TargetCreated += TargetCreated;
+            var page2Task = browserOne.NewPageAsync();
+
+            await Task.WhenAll(tcs.Task, page2Task);
+            var page1 = tcs.Task.Result;
+            var page2 = page2Task.Result;
+
+            Assert.Equal(56, await page1.EvaluateExpressionAsync<int>("7 * 8"));
+            Assert.Equal(42, await page1.EvaluateExpressionAsync<int>("7 * 6"));
+            await browserOne.CloseAsync();
+        }
         [Fact]
         public async Task ShouldSupportCustomWebSocket()
         {

lib/PuppeteerSharp/DOMWorld.cs

@@ -47,6 +47,8 @@ internal void SetContext(ExecutionContext context)
             }
         }
 
+        internal bool HasContext => _contextResolveTaskWrapper?.Task.IsCompleted == true;
+
         internal void Detach()
         {
             _detached = true;

lib/PuppeteerSharp/FrameManager.cs

@@ -258,8 +258,11 @@ private async Task OnExecutionContextCreatedAsync(ContextPayload contextPayload)
                 {
                     world = frame.MainWorld;
                 }
-                else if (contextPayload.Name == UtilityWorldName)
+                else if (contextPayload.Name == UtilityWorldName && !frame.SecondaryWorld.HasContext)
                 {
+                    // In case of multiple sessions to the same target, there's a race between
+                    // connections so we might end up creating multiple isolated worlds.
+                    // We can use either.
                     world = frame.SecondaryWorld;
                 }
             }