Initial integration of codespace URL rewriting logic into hosting. (#…

…6183)

* Initial integration of codespace URL rewriting logic into hosting.

* Add unit tests.

* Update src/Aspire.Hosting/Codespaces/CodespacesUrlRewriter.cs

Co-authored-by: James Newton-King <[email protected]>

* PR feedback.

* Share config acquisition logic/exceptions.

* Update src/Aspire.Hosting/Codespaces/CodespacesUrlRewriter.cs

Co-authored-by: James Newton-King <[email protected]>

---------

Co-authored-by: James Newton-King <[email protected]>

src/Aspire.Hosting/Codespaces/CodespacesUrlRewriter.cs

@@ -0,0 +1,89 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Collections.Immutable;
+using Aspire.Hosting.ApplicationModel;
+using Microsoft.Extensions.Configuration;
+using Microsoft.Extensions.Hosting;
+using Microsoft.Extensions.Logging;
+
+namespace Aspire.Hosting.Codespaces;
+
+internal sealed class CodespacesUrlRewriter(ILogger<CodespacesUrlRewriter> logger, IConfiguration configuration, ResourceNotificationService resourceNotificationService) : BackgroundService
+{
+    private const string CodespacesEnvironmentVariable = "CODESPACES";
+    private const string CodespaceNameEnvironmentVariable = "CODESPACE_NAME";
+    private const string GitHubCodespacesPortForwardingDomain = "GITHUB_CODESPACES_PORT_FORWARDING_DOMAIN";
+
+    private string GetRequiredCodespacesConfigurationValue(string key)
+    {
+        ArgumentNullException.ThrowIfNullOrEmpty(key);
+        return configuration.GetValue<string>(key) ?? throw new DistributedApplicationException($"Codespaces was detected but {key} environment missing.");
+    }
+
+    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
+    {
+        if (!configuration.GetValue<bool>(CodespacesEnvironmentVariable, false))
+        {
+            logger.LogTrace("Not running in Codespaces, skipping URL rewriting.");
+            return;
+        }
+
+        var gitHubCodespacesPortForwardingDomain = GetRequiredCodespacesConfigurationValue(GitHubCodespacesPortForwardingDomain);
+        var codespaceName = GetRequiredCodespacesConfigurationValue(CodespaceNameEnvironmentVariable);
+
+        do
+        {
+            try
+            {
+                var resourceEvents = resourceNotificationService.WatchAsync(stoppingToken);
+
+                await foreach (var resourceEvent in resourceEvents.ConfigureAwait(false))
+                {
+                    Dictionary<UrlSnapshot, UrlSnapshot>? remappedUrls = null;
+
+                    foreach (var originalUrlSnapshot in resourceEvent.Snapshot.Urls)
+                    {
+                        var uri = new Uri(originalUrlSnapshot.Url);
+
+                        if (!originalUrlSnapshot.IsInternal && (uri.Scheme == "http" || uri.Scheme == "https") && uri.Host == "localhost")
+                        {
+                            remappedUrls ??= new();
+
+                            var newUrlSnapshot = originalUrlSnapshot with
+                            {
+                                // The format of GitHub Codespaces URLs comprises the codespace
+                                // name (from the CODESPACE_NAME environment variable, the port,
+                                // and the port forwarding domain (via GITHUB_CODESPACES_PORT_FORWARDING_DOMAIN
+                                // which is typically ".app.github.dev". The VSCode instance is typically
+                                // hosted at codespacename.github.dev whereas the forwarded ports
+                                // would be at codespacename-port.app.github.dev.
+                                Url = $"{uri.Scheme}://{codespaceName}-{uri.Port}.{gitHubCodespacesPortForwardingDomain}{uri.AbsolutePath}"
+                            };
+
+                            remappedUrls.Add(originalUrlSnapshot, newUrlSnapshot);
+                        }
+                    }
+
+                    if (remappedUrls is not null)
+                    {
+                        var transformedUrls = from originalUrl in resourceEvent.Snapshot.Urls
+                                              select remappedUrls.TryGetValue(originalUrl, out var remappedUrl) ? remappedUrl : originalUrl;
+
+                        await resourceNotificationService.PublishUpdateAsync(resourceEvent.Resource, resourceEvent.ResourceId, s => s with
+                        {
+                            Urls = transformedUrls.ToImmutableArray()
+                        }).ConfigureAwait(false);
+                    }
+                }
+            }
+            catch (Exception ex) when (!stoppingToken.IsCancellationRequested)
+            {
+                // When debugging sometimes we'll get cancelled here but we don't want
+                // to tear down the loop. We only want to crash out when the service's
+                // cancellation token is signaled.
+                logger.LogTrace(ex, "Codespace URL rewriting loop threw an exception but was ignored.");
+            }
+        } while (!stoppingToken.IsCancellationRequested);
+    }
+}

src/Aspire.Hosting/DistributedApplicationBuilder.cs

@@ -6,6 +6,7 @@
 using System.Security.Cryptography;
 using System.Text;
 using Aspire.Hosting.ApplicationModel;
+using Aspire.Hosting.Codespaces;
 using Aspire.Hosting.Dashboard;
 using Aspire.Hosting.Dcp;
 using Aspire.Hosting.Eventing;
@@ -267,6 +268,9 @@ public DistributedApplicationBuilder(DistributedApplicationOptions options)
             _innerBuilder.Services.AddSingleton(new Locations());
             _innerBuilder.Services.AddSingleton<IKubernetesService, KubernetesService>();
 
+            // Codespaces
+            _innerBuilder.Services.AddHostedService<CodespacesUrlRewriter>();
+
             Eventing.Subscribe<BeforeStartEvent>(BuiltInDistributedApplicationEventSubscriptionHandlers.InitializeDcpAnnotations);
         }
 

tests/Aspire.Hosting.Tests/Codespaces/CodespacesUrlRewriterTests.cs

@@ -0,0 +1,103 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using Aspire.Hosting.Utils;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Logging;
+using Xunit;
+using Xunit.Abstractions;
+
+namespace Aspire.Hosting.Tests.Codespaces;
+
+public class CodespacesUrlRewriterTests(ITestOutputHelper testOutputHelper)
+{
+    [Fact]
+    public async Task VerifyUrlsRewriterStopsWhenNotInCodespaces()
+    {
+        using var builder = TestDistributedApplicationBuilder.Create(testOutputHelper);
+        builder.Services.AddLogging(logging =>
+        {
+            logging.AddFakeLogging();
+            logging.AddXunit(testOutputHelper);
+        });
+
+        var resource = builder.AddResource(new CustomResource("resource"));
+
+        var abortToken = new CancellationTokenSource(TimeSpan.FromSeconds(60));
+
+        using var app = builder.Build();
+        var rns = app.Services.GetRequiredService<ResourceNotificationService>();
+
+        await app.StartAsync(abortToken.Token);
+
+        var collector = app.Services.GetFakeLogCollector();
+
+        var urlRewriterStopped = false;
+
+        while (!abortToken.Token.IsCancellationRequested)
+        {
+            var logs = collector.GetSnapshot();
+            urlRewriterStopped = logs.Any(l => l.Message.Contains("Not running in Codespaces, skipping URL rewriting."));
+            if (urlRewriterStopped)
+            {
+                break;
+            }
+        }
+
+        Assert.True(urlRewriterStopped);
+
+        await app.StopAsync(abortToken.Token);
+    }
+
+    [Fact]
+    public async Task VerifyUrlsRewrittenWhenInCodespaces()
+    {
+        using var builder = TestDistributedApplicationBuilder.Create(testOutputHelper);
+
+        builder.Configuration["CODESPACES"] = "true";
+        builder.Configuration["GITHUB_CODESPACES_PORT_FORWARDING_DOMAIN"] = "app.github.dev";
+        builder.Configuration["CODESPACE_NAME"] = "test-codespace";
+
+        var resource = builder.AddResource(new CustomResource("resource"));
+
+        var abortToken = new CancellationTokenSource(TimeSpan.FromSeconds(60));
+
+        using var app = builder.Build();
+        var rns = app.Services.GetRequiredService<ResourceNotificationService>();
+
+        await app.StartAsync(abortToken.Token);
+
+        // Push the URL to the resource state.
+        var localhostUrlSnapshot = new UrlSnapshot("Test", "http://localhost:1234", false);
+        await rns.PublishUpdateAsync(resource.Resource, s => s with
+        {
+            State = KnownResourceStates.Running,
+            Urls = [localhostUrlSnapshot]
+        });
+
+        // Wait until
+        var resourceEvent = await rns.WaitForResourceAsync(
+            resource.Resource.Name,
+            (re) => {
+                var match = re.Snapshot.Urls.Length > 0 && re.Snapshot.Urls[0].Url.Contains("app.github.dev");
+                return match;
+            },
+            abortToken.Token);
+
+        Assert.Collection(
+            resourceEvent.Snapshot.Urls,
+            u =>
+            {
+                Assert.Equal("Test", u.Name);
+                Assert.Equal("http://test-codespace-1234.app.github.dev/", u.Url);
+                Assert.False(u.IsInternal);
+            }
+            );
+
+        await app.StopAsync(abortToken.Token);
+    }
+
+    private sealed class CustomResource(string name) : Resource(name)
+    {
+    }
+}