Fix endpoints not being available in debug view until after WebApplication starts (#49103)

Author: JamesNK

src/DefaultBuilder/src/WebApplication.cs

@@ -3,6 +3,7 @@
 
 using System.Diagnostics;
 using System.Diagnostics.CodeAnalysis;
+using System.Linq;
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.Hosting.Server;
 using Microsoft.AspNetCore.Hosting.Server.Features;
@@ -259,7 +260,30 @@ internal sealed class WebApplicationDebugView(WebApplication webApplication)
         public IHostApplicationLifetime Lifetime => _webApplication.Lifetime;
         public ILogger Logger => _webApplication.Logger;
         public string Urls => string.Join(", ", _webApplication.Urls);
-        public IReadOnlyList<Endpoint> Endpoints => _webApplication.Services.GetRequiredService<EndpointDataSource>().Endpoints;
+        public IReadOnlyList<Endpoint> Endpoints
+        {
+            get
+            {
+                var dataSource = _webApplication.Services.GetRequiredService<EndpointDataSource>();
+                if (dataSource is CompositeEndpointDataSource compositeEndpointDataSource)
+                {
+                    // The web app's data sources aren't registered until the routing middleware is. That often happens when the app is run.
+                    // We want endpoints to be available in the debug view before the app starts. Test if all the web app's the data sources are registered.
+                    if (compositeEndpointDataSource.DataSources.Intersect(_webApplication.DataSources).Count() == _webApplication.DataSources.Count)
+                    {
+                        // Data sources are centrally registered.
+                        return dataSource.Endpoints;
+                    }
+                    else
+                    {
+                        // Fallback to just the web app's data sources to support debugging before the web app starts.
+                        return new CompositeEndpointDataSource(_webApplication.DataSources).Endpoints;
+                    }
+                }
+
+                return dataSource.Endpoints;
+            }
+        }
         public bool IsRunning => _webApplication.IsRunning;
         public IList<string>? Middleware
         {

src/DefaultBuilder/test/Microsoft.AspNetCore.Tests/WebApplicationTests.cs

@@ -17,6 +17,7 @@
 using Microsoft.AspNetCore.Hosting.Server.Features;
 using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Http.Features;
+using Microsoft.AspNetCore.Http.Metadata;
 using Microsoft.AspNetCore.Routing;
 using Microsoft.AspNetCore.Routing.Constraints;
 using Microsoft.AspNetCore.TestHost;
@@ -2536,7 +2537,7 @@ private sealed class TestDebugger : IDebugger
     }
 
     [Fact]
-    public void UseMiddleware_DebugView_HasMiddleware()
+    public void DebugView_UseMiddleware_HasMiddleware()
     {
         var builder = WebApplication.CreateBuilder();
         builder.Services.AddSingleton<IDebugger>(new TestDebugger(true));
@@ -2561,13 +2562,13 @@ public void UseMiddleware_DebugView_HasMiddleware()
             m => Assert.Equal("Microsoft.AspNetCore.Authentication.AuthenticationMiddleware", m),
             m =>
             {
-                Assert.Contains(nameof(UseMiddleware_DebugView_HasMiddleware), m);
+                Assert.Contains(nameof(DebugView_UseMiddleware_HasMiddleware), m);
                 Assert.DoesNotContain(nameof(RequestDelegate), m);
             });
     }
 
     [Fact]
-    public void NoDebugger_DebugView_NoMiddleware()
+    public void DebugView_NoDebugger_NoMiddleware()
     {
         var builder = WebApplication.CreateBuilder();
         builder.Services.AddSingleton<IDebugger>(new TestDebugger(false));
@@ -2587,7 +2588,7 @@ public void NoDebugger_DebugView_NoMiddleware()
     }
 
     [Fact]
-    public async Task UseMiddleware_HasEndpointsAndAuth_Run_DebugView_HasAutomaticMiddleware()
+    public async Task DebugView_UseMiddleware_HasEndpointsAndAuth_Run_HasAutomaticMiddleware()
     {
         var builder = WebApplication.CreateBuilder();
         builder.WebHost.UseTestServer();
@@ -2615,7 +2616,7 @@ public async Task UseMiddleware_HasEndpointsAndAuth_Run_DebugView_HasAutomaticMi
     }
 
     [Fact]
-    public async Task NoMiddleware_Run_DebugView_HasAutomaticMiddleware()
+    public async Task DebugView_NoMiddleware_Run_HasAutomaticMiddleware()
     {
         var builder = WebApplication.CreateBuilder();
         builder.WebHost.UseTestServer();
@@ -2633,7 +2634,7 @@ public async Task NoMiddleware_Run_DebugView_HasAutomaticMiddleware()
     }
 
     [Fact]
-    public void NestedMiddleware_DebugView_OnlyContainsTopLevelMiddleware()
+    public void DebugView_NestedMiddleware_OnlyContainsTopLevelMiddleware()
     {
         var builder = WebApplication.CreateBuilder();
         builder.Services.AddSingleton<IDebugger>(new TestDebugger(true));
@@ -2655,6 +2656,50 @@ public void NestedMiddleware_DebugView_OnlyContainsTopLevelMiddleware()
         Assert.Equal(3, debugView.Middleware.Count);
     }
 
+    [Fact]
+    public async Task DebugView_Endpoints_AvailableBeforeAndAfterStart()
+    {
+        var builder = WebApplication.CreateBuilder();
+
+        await using var app = builder.Build();
+        app.MapGet("/hello", () => "hello world");
+
+        var debugView = new WebApplication.WebApplicationDebugView(app);
+
+        Assert.Collection(debugView.Endpoints,
+            ep => Assert.Equal("/hello", ep.Metadata.GetRequiredMetadata<IRouteDiagnosticsMetadata>().Route));
+
+        // Starting the app registers endpoint data sources with routing.
+        _ = app.RunAsync();
+
+        Assert.Collection(debugView.Endpoints,
+            ep => Assert.Equal("/hello", ep.Metadata.GetRequiredMetadata<IRouteDiagnosticsMetadata>().Route));
+    }
+
+    [Fact]
+    public async Task DebugView_Endpoints_UseEndpoints_AvailableBeforeAndAfterStart()
+    {
+        var builder = WebApplication.CreateBuilder();
+
+        await using var app = builder.Build();
+        app.UseRouting();
+        app.UseEndpoints(endpoints =>
+        {
+            endpoints.MapGet("/hello", () => "hello world");
+        });
+
+        var debugView = new WebApplication.WebApplicationDebugView(app);
+
+        Assert.Collection(debugView.Endpoints,
+            ep => Assert.Equal("/hello", ep.Metadata.GetRequiredMetadata<IRouteDiagnosticsMetadata>().Route));
+
+        // Starting the app registers endpoint data sources with routing.
+        _ = app.RunAsync();
+
+        Assert.Collection(debugView.Endpoints,
+            ep => Assert.Equal("/hello", ep.Metadata.GetRequiredMetadata<IRouteDiagnosticsMetadata>().Route));
+    }
+
     private class MiddlewareWithInterface : IMiddleware
     {
         public Task InvokeAsync(HttpContext context, RequestDelegate next)