Restore dotnet watch dashboard auto-launch signal

src/Shared/LoggingHelpers.cs

@@ -37,6 +37,12 @@ public static void WriteDashboardSummary(ILogger logger, string? dashboardUrl, s
             ? $"{dashboardAuthority}/login?t={token}"
             : null;
 
+        if (loginUrl is not null)
+        {
+            // The template format string "Login to the dashboard at {LoginUrl}" is the contract with dotnet watch. Do not change it.
+            logger.LogInformation("Login to the dashboard at {LoginUrl}", loginUrl);
+        }
+
         var templateBuilder = new StringBuilder();
         var parameters = new List<object?>();
 

tests/Aspire.Dashboard.Tests/Integration/FrontendBrowserTokenAuthTests.cs

@@ -405,6 +405,15 @@ public async Task LogOutput_NoToken_GeneratedTokenLogged()
                 Assert.Equal(LogLevel.Warning, w.LogLevel);
             },
             w =>
+            {
+                Assert.Equal("Login to the dashboard at {LoginUrl}", LogTestHelpers.GetValue(w, "{OriginalFormat}"));
+
+                var loginUrl = (string)LogTestHelpers.GetValue(w, "LoginUrl")!;
+                var uri = new Uri(loginUrl, UriKind.Absolute);
+                var queryString = HttpUtility.ParseQueryString(uri.Query);
+                Assert.NotNull(queryString["t"]);
+            },
+            w =>
             {
                 Assert.StartsWith("Aspire Dashboard", (string)LogTestHelpers.GetValue(w, "{OriginalFormat}")!);
 

tests/Aspire.Dashboard.Tests/LoggingHelpersTests.cs

@@ -23,7 +23,15 @@ public void WriteDashboardSummary_WithTokenAndOtlpEndpoints_LogsSummaryAndStruct
             "http://localhost:18890",
             "abc123");
 
-        var write = Assert.Single(sink.Writes);
+        Assert.Equal(2, sink.Writes.Count);
+
+        var loginWrite = sink.Writes.ElementAt(0);
+        Assert.Equal(LogLevel.Information, loginWrite.LogLevel);
+        Assert.Equal("Login to the dashboard at http://localhost:18888/login?t=abc123", loginWrite.Message);
+        Assert.Equal("Login to the dashboard at {LoginUrl}", LogTestHelpers.GetValue(loginWrite, "{OriginalFormat}"));
+        Assert.Equal("http://localhost:18888/login?t=abc123", LogTestHelpers.GetValue(loginWrite, "LoginUrl"));
+
+        var write = sink.Writes.ElementAt(1);
         Assert.Equal(LogLevel.Information, write.LogLevel);
         Assert.NotNull(write.Message);
         var lines = GetMessageLines(write.Message!);
@@ -169,7 +177,9 @@ public void WriteDashboardSummary_WithoutOtlpEndpoints_DoesNotIncludeOtlpLines()
             otlpHttpUrl: null,
             token: "abc123");
 
-        var write = Assert.Single(sink.Writes);
+        Assert.Equal(2, sink.Writes.Count);
+
+        var write = sink.Writes.ElementAt(1);
         Assert.NotNull(write.Message);
         var lines = GetMessageLines(write.Message!);
 
@@ -198,8 +208,9 @@ public void WriteDashboardSummary_IsContainer_IncludesContainerMessage()
             token: "abc123",
             isContainer: true);
 
-        Assert.Equal(2, sink.Writes.Count);
-        var containerWrite = sink.Writes.Skip(1).First();
+        Assert.Equal(3, sink.Writes.Count);
+
+        var containerWrite = sink.Writes.ElementAt(2);
         Assert.Equal("Dashboard is running in a container. Access the dashboard from the host using port forwarding.", containerWrite.Message);
     }
 

tests/Aspire.Hosting.Tests/Dashboard/DashboardEventHandlersTests.cs

@@ -271,6 +271,12 @@ public async Task ResourceReadyEvent_LogsDashboardUrlFromAllocatedEndpoint(strin
         Assert.Equal(allocatedPort, uri.Port);
         Assert.Equal(expectedScheme, uri.Scheme);
 
+        var loginLog = testSink.Writes.FirstOrDefault(l =>
+            LogTestHelpers.GetValue(l, "{OriginalFormat}")?.ToString() == "Login to the dashboard at {LoginUrl}");
+
+        Assert.NotNull(loginLog);
+        Assert.Equal($"{expectedScheme}://{expectedHost}:{allocatedPort}/login?t=test-token", LogTestHelpers.GetValue(loginLog, "LoginUrl"));
+
         var summaryLog = testSink.Writes.FirstOrDefault(l =>
             LogTestHelpers.GetValue(l, "{OriginalFormat}")?.ToString()?.Contains("OTLP/gRPC:") == true);