Add support for global conventions on WebApplication

src/DefaultBuilder/src/PublicAPI.Unshipped.txt

@@ -1 +1,2 @@
 #nullable enable
+Microsoft.AspNetCore.Builder.WebApplication.Conventions.get -> Microsoft.AspNetCore.Builder.IEndpointConventionBuilder!

src/DefaultBuilder/src/WebApplication.cs

@@ -27,15 +27,20 @@ public sealed class WebApplication : IHost, IApplicationBuilder, IEndpointRouteB
     internal const string GlobalEndpointRouteBuilderKey = "__GlobalEndpointRouteBuilder";
 
     private readonly IHost _host;
-    private readonly List<EndpointDataSource> _dataSources = new();
+    private readonly GlobalEndpointRouteBuilder _globalEndpointRouteBuilder;
+    private readonly RouteGroupBuilder _globalRouteGroupBuilder;
 
     internal WebApplication(IHost host)
     {
         _host = host;
+
+        _globalEndpointRouteBuilder = new(this);
+        _globalRouteGroupBuilder = _globalEndpointRouteBuilder.MapGroup(string.Empty);
+
         ApplicationBuilder = new ApplicationBuilder(host.Services, ServerFeatures);
         Logger = host.Services.GetRequiredService<ILoggerFactory>().CreateLogger(Environment.ApplicationName ?? nameof(WebApplication));
 
-        Properties[GlobalEndpointRouteBuilderKey] = this;
+        Properties[GlobalEndpointRouteBuilderKey] = _globalEndpointRouteBuilder;
     }
 
     /// <summary>
@@ -80,9 +85,14 @@ IServiceProvider IApplicationBuilder.ApplicationServices
     internal IDictionary<string, object?> Properties => ApplicationBuilder.Properties;
     IDictionary<string, object?> IApplicationBuilder.Properties => Properties;
 
-    internal ICollection<EndpointDataSource> DataSources => _dataSources;
+    internal ICollection<EndpointDataSource> DataSources => ((IEndpointRouteBuilder)_globalRouteGroupBuilder).DataSources;
     ICollection<EndpointDataSource> IEndpointRouteBuilder.DataSources => DataSources;
 
+    /// <summary>
+    /// Gets the <see cref="IEndpointConventionBuilder"/> for the application.
+    /// </summary>
+    public IEndpointConventionBuilder Conventions => _globalRouteGroupBuilder;
+
     internal ApplicationBuilder ApplicationBuilder { get; }
 
     IServiceProvider IEndpointRouteBuilder.ServiceProvider => Services;
@@ -307,4 +317,13 @@ public IList<string>? Middleware
             }
         }
     }
+
+    private sealed class GlobalEndpointRouteBuilder(WebApplication application) : IEndpointRouteBuilder
+    {
+        public IServiceProvider ServiceProvider => application.Services;
+
+        public ICollection<EndpointDataSource> DataSources { get; } = [];
+
+        public IApplicationBuilder CreateApplicationBuilder() => ((IApplicationBuilder)application).New();
+    }
 }

src/DefaultBuilder/src/WebApplicationBuilder.cs

@@ -407,8 +407,10 @@ private void ConfigureApplication(WebHostBuilderContext context, IApplicationBui
         // destination.Run(source)
         // destination.UseEndpoints()
 
-        // Set the route builder so that UseRouting will use the WebApplication as the IEndpointRouteBuilder for route matching
-        app.Properties.Add(WebApplication.GlobalEndpointRouteBuilderKey, _builtApplication);
+        // Set the route builder so that UseRouting will use the RouteGroupBuilder managed
+        // by the WebApplication as the IEndpointRouteBuilder instance
+        var globalRouteGroupBuilder = _builtApplication.Properties[WebApplication.GlobalEndpointRouteBuilderKey];
+        app.Properties.Add(WebApplication.GlobalEndpointRouteBuilderKey, globalRouteGroupBuilder);
 
         // Only call UseRouting() if there are endpoints configured and UseRouting() wasn't called on the global route builder already
         if (_builtApplication.DataSources.Count > 0)

src/DefaultBuilder/test/Microsoft.AspNetCore.Tests/Microsoft.AspNetCore.Tests.csproj

@@ -6,6 +6,10 @@
 
   <ItemGroup>
     <Reference Include="Microsoft.AspNetCore" />
+    <Reference Include="Microsoft.AspNetCore.SignalR" />
+    <Reference Include="Microsoft.AspNetCore.Components.Endpoints" />
+    <Reference Include="Microsoft.AspNetCore.Mvc" />
+    <Reference Include="Microsoft.AspNetCore.Mvc.Core" />
     <Reference Include="Microsoft.AspNetCore.TestHost" />
     <Reference Include="Microsoft.AspNetCore.Authorization.Policy" />
     <Content Include="Microsoft.AspNetCore.TestHost.StaticWebAssets.xml" CopyToOutputDirectory="PreserveNewest" />