Continue printing out redirected process output after we detect browser launch URL. (#44290)

Author: tmat

src/BuiltInTools/dotnet-watch/Browser/BrowserConnector.cs

@@ -112,20 +112,27 @@ public bool TryGetRefreshServer(ProjectGraphNode projectNode, [NotNullWhen(true)
                 return null;
             }
 
+            bool matchFound = false;
+
             return handler;
 
             void handler(object sender, DataReceivedEventArgs eventArgs)
             {
                 // We've redirected the output, but want to ensure that it continues to appear in the user's console.
                 Console.WriteLine(eventArgs.Data);
 
+                if (matchFound)
+                {
+                    return;
+                }
+
                 var match = s_nowListeningRegex.Match(eventArgs.Data ?? "");
                 if (!match.Success)
                 {
                     return;
                 }
 
-                ((Process)sender).OutputDataReceived -= handler;
+                matchFound = true;
 
                 var projectAddedToAttemptedSet = ImmutableInterlocked.Update(ref _browserLaunchAttempted, static (set, projectNode) => set.Add(projectNode), projectNode);
                 if (projectAddedToAttemptedSet)

test/dotnet-watch.Tests/Watch/BrowserLaunchTests.cs

@@ -22,8 +22,14 @@ public async Task LaunchesBrowserOnStart()
 
             App.Start(testAsset, [], testFlags: TestFlags.MockBrowser);
 
+            // check that all app output is printed out:
+            await App.AssertOutputLine(line => line.Contains("Content root path:"));
+
+            Assert.Contains(App.Process.Output, line => line.Contains("Application started. Press Ctrl+C to shut down."));
+            Assert.Contains(App.Process.Output, line => line.Contains("Hosting environment: Development"));
+
             // Verify we launched the browser.
-            await App.AssertOutputLineStartsWith("dotnet watch ⌚ Launching browser: https://localhost:5001/");
+            Assert.Contains(App.Process.Output, line => line.Contains("dotnet watch ⌚ Launching browser: https://localhost:5001/"));
         }
 
         [Fact]