dotnet watch doesn't launch browser correctly if the listening URL has a trailing slash

[eerhardt]

Describe the bug

When using dotnet watch, it parses the console output for Now listening on: <URL>. See:

sdk/src/BuiltInTools/dotnet-watch/Filters/LaunchBrowserFilter.cs

Line 13 in 91271e3

private static readonly Regex NowListeningRegex = new(@"Now listening on: (?<url>.*)\s*$", RegexOptions.None | RegexOptions.Compiled, TimeSpan.FromSeconds(10));

sdk/src/BuiltInTools/dotnet-watch/Filters/LaunchBrowserFilter.cs

Lines 72 to 88 in 91271e3

	var match = NowListeningRegex.Match(eventArgs.Data);
	if (match.Success)
	{
	var launchUrl = match.Groups["url"].Value;
	var process = (Process)sender;
	process.OutputDataReceived -= OnOutput;
	if (!_attemptedBrowserLaunch)
	{
	_attemptedBrowserLaunch = true;
	_reporter.Verbose("Launching browser.");
	try
	{
	LaunchBrowser(launchUrl);

When this URL has a trailing slash like Now listening on: http://localhost:15888/, the browser launches, but the page is broken:

The code is always appending a /, which is causing the issue:

sdk/src/BuiltInTools/dotnet-watch/Filters/LaunchBrowserFilter.cs

Lines 114 to 118 in 91271e3

	private void LaunchBrowser(string launchUrl)
	{
	Debug.Assert(_reporter != null);
	var fileName = Uri.TryCreate(_launchPath, UriKind.Absolute, out _) ? _launchPath : launchUrl + "/" + _launchPath;

To Reproduce

Have a web app that writes Now listening on: http://localhost:15888/ to the console. dotnet watch it and notice the browser launches, but doesn't hit the endpoint correctly.

[dotnet-issue-labeler]

I couldn't figure out the best area label to add to this issue. If you have write-permissions please help me learn by adding exactly one area label.

[ShreyasJejurkar]

So I just tried to repro this on .NET SDK 8.0.100, but it did not reproduce, following are the steps I did.

1. Create a new web app with dotnet new web.
2. Then I went to Properties/launchsettings.json folder and edited it just to have the below content.

{
  "$schema": "http://json.schemastore.org/launchsettings.json",
  "iisSettings": {
    "windowsAuthentication": false,
    "anonymousAuthentication": true,
    "iisExpress": {
      "applicationUrl": "http://localhost:2691",
      "sslPort": 44306
    }
  },
  "profiles": {
    "http": {
      "commandName": "Project",
      "dotnetRunMessages": true,
      "launchBrowser": true,
      "applicationUrl": "http://localhost:5039/", // <-- edited this manually, to add trailing slash for repro
      "environmentVariables": {
        "ASPNETCORE_ENVIRONMENT": "Development"
      }
    }
  }
}

3. And then I ran dotnet watch from the project folder and indeed it launched the browser with the correct URL http://localhost:5039/
   

4. And on the console, I do see the URL without trailing slash
   

Please let me know if I am missing anywhere as part of repro steps.

[eerhardt]

Here's a simple repro:

1. dotnet new web
2. Change the Program.cs file to be:

var builder = WebApplication.CreateBuilder(args);
builder.Logging.ClearProviders();

var app = builder.Build();
app.Lifetime.ApplicationStarted.Register(() => Console.WriteLine("Now listening on: http://localhost:7126/"));

app.MapGet("/", () => "Hello World!");

app.Run();

(you can change the port number to whatever number you have in your launchSettings.json).

3. dotnet watch

You'll see

And when the browser launches, it will have 2 trailing slashes, like in the picture in the original post.

[tmat]

Fixed by #46100