Provide work around for ASP.NET Core bug 41773. Resolves #830

Author: commonsensesoftware

src/AspNetCore/WebApi/src/Asp.Versioning.Mvc.ApiExplorer/ApiVersionParameterDescriptionContext.cs

@@ -8,6 +8,7 @@ namespace Asp.Versioning.ApiExplorer;
 using Microsoft.AspNetCore.Mvc.ModelBinding;
 using Microsoft.AspNetCore.Routing;
 using Microsoft.AspNetCore.Routing.Patterns;
+using Microsoft.AspNetCore.Routing.Template;
 using static Asp.Versioning.ApiVersionParameterLocation;
 using static System.Linq.Enumerable;
 using static System.StringComparison;
@@ -43,6 +44,11 @@ public ApiVersionParameterDescriptionContext(
         optional = options.AssumeDefaultVersionWhenUnspecified && apiVersion == options.DefaultApiVersion;
     }
 
+    // intentionally an internal property so the public contract doesn't change. this will be removed
+    // once the ASP.NET Core team fixes the bug
+    // BUG: https://github.com/dotnet/aspnetcore/issues/41773
+    internal IInlineConstraintResolver? ConstraintResolver { get; set; }
+
     /// <summary>
     /// Gets the associated API description.
     /// </summary>
@@ -160,7 +166,8 @@ protected virtual void AddHeader( string name )
     protected virtual void UpdateUrlSegment()
     {
         var parameter = FindByRouteConstraintType( ApiDescription ) ??
-                        FindByRouteConstraintName( ApiDescription, Options.RouteConstraintName );
+                        FindByRouteConstraintName( ApiDescription, Options.RouteConstraintName ) ??
+                        TryCreateFromRouteTemplate( ApiDescription, ConstraintResolver );
 
         if ( parameter == null )
         {
@@ -309,6 +316,73 @@ routeInfo.Constraints is IEnumerable<IRouteConstraint> constraints &&
         return default;
     }
 
+    private static ApiParameterDescription? TryCreateFromRouteTemplate( ApiDescription description, IInlineConstraintResolver? constraintResolver )
+    {
+        if ( constraintResolver == null )
+        {
+            return default;
+        }
+
+        var relativePath = description.RelativePath;
+
+        if ( string.IsNullOrEmpty( relativePath ) )
+        {
+            return default;
+        }
+
+        var constraints = new List<IRouteConstraint>();
+        var template = TemplateParser.Parse( relativePath );
+        var constraintName = default( string );
+
+        for ( var i = 0; i < template.Parameters.Count; i++ )
+        {
+            var match = false;
+            var parameter = template.Parameters[i];
+
+            foreach ( var inlineConstraint in parameter.InlineConstraints )
+            {
+                var constraint = constraintResolver.ResolveConstraint( inlineConstraint.Constraint )!;
+
+                constraints.Add( constraint );
+
+                if ( constraint is ApiVersionRouteConstraint )
+                {
+                    match = true;
+                    constraintName = inlineConstraint.Constraint;
+                }
+            }
+
+            if ( !match )
+            {
+                continue;
+            }
+
+            constraints.TrimExcess();
+
+            // ASP.NET Core does not discover route parameters without using Reflection in 6.0. unclear if it will be fixed before 7.0
+            // BUG: https://github.com/dotnet/aspnetcore/issues/41773
+            // REF: https://github.com/dotnet/aspnetcore/blob/release/6.0/src/Mvc/Mvc.ApiExplorer/src/DefaultApiDescriptionProvider.cs#L323
+            var result = new ApiParameterDescription()
+            {
+                Name = parameter.Name!,
+                RouteInfo = new()
+                {
+                    Constraints = constraints,
+                    DefaultValue = parameter.DefaultValue,
+                    IsOptional = parameter.IsOptional || parameter.DefaultValue != null,
+                },
+                Source = BindingSource.Path,
+            };
+            var token = $"{parameter.Name}:{constraintName}";
+
+            description.RelativePath = relativePath.Replace( token, parameter.Name, Ordinal );
+            description.ParameterDescriptions.Insert( 0, result );
+            return result;
+        }
+
+        return default;
+    }
+
     private ApiParameterDescription NewApiVersionParameter( string name, BindingSource source )
     {
         var parameter = new ApiParameterDescription()

src/AspNetCore/WebApi/src/Asp.Versioning.Mvc.ApiExplorer/DependencyInjection/IApiVersioningBuilderExtensions.cs

@@ -5,6 +5,8 @@ namespace Microsoft.Extensions.DependencyInjection;
 using Asp.Versioning;
 using Asp.Versioning.ApiExplorer;
 using Microsoft.AspNetCore.Mvc.ApiExplorer;
+using Microsoft.AspNetCore.Mvc.ModelBinding;
+using Microsoft.AspNetCore.Routing;
 using Microsoft.Extensions.DependencyInjection.Extensions;
 using Microsoft.Extensions.Options;
 using static ServiceDescriptor;
@@ -60,6 +62,15 @@ private static void AddApiExplorerServices( IServiceCollection services )
         services.AddMvcCore().AddApiExplorer();
         services.TryAddSingleton<IOptionsFactory<ApiExplorerOptions>, ApiExplorerOptionsFactory<ApiExplorerOptions>>();
         services.TryAddSingleton<IApiVersionDescriptionProvider, DefaultApiVersionDescriptionProvider>();
-        services.TryAddEnumerable( Transient<IApiDescriptionProvider, VersionedApiDescriptionProvider>() );
+
+        // use internal constructor until ASP.NET Core fixes their bug
+        // BUG: https://github.com/dotnet/aspnetcore/issues/41773
+        services.TryAddEnumerable(
+            Transient<IApiDescriptionProvider, VersionedApiDescriptionProvider>(
+                sp => new(
+                    sp.GetRequiredService<ISunsetPolicyManager>(),
+                    sp.GetRequiredService<IModelMetadataProvider>(),
+                    sp.GetRequiredService<IInlineConstraintResolver>(),
+                    sp.GetRequiredService<IOptions<ApiExplorerOptions>>() ) ) );
     }
 }

src/AspNetCore/WebApi/src/Asp.Versioning.Mvc.ApiExplorer/VersionedApiDescriptionProvider.cs

@@ -2,10 +2,12 @@
 
 namespace Asp.Versioning.ApiExplorer;
 
+using Asp.Versioning.Routing;
 using Microsoft.AspNetCore.Mvc.Abstractions;
 using Microsoft.AspNetCore.Mvc.ApiExplorer;
 using Microsoft.AspNetCore.Mvc.Controllers;
 using Microsoft.AspNetCore.Mvc.ModelBinding;
+using Microsoft.AspNetCore.Routing;
 using Microsoft.Extensions.Options;
 using static Asp.Versioning.ApiVersionMapping;
 using static System.Globalization.CultureInfo;
@@ -18,6 +20,7 @@ namespace Asp.Versioning.ApiExplorer;
 public class VersionedApiDescriptionProvider : IApiDescriptionProvider
 {
     private readonly IOptions<ApiExplorerOptions> options;
+    private readonly IInlineConstraintResolver constraintResolver;
     private ApiVersionModelMetadata? modelMetadata;
 
     /// <summary>
@@ -31,9 +34,19 @@ public VersionedApiDescriptionProvider(
         ISunsetPolicyManager sunsetPolicyManager,
         IModelMetadataProvider modelMetadataProvider,
         IOptions<ApiExplorerOptions> options )
+        : this( sunsetPolicyManager, modelMetadataProvider, new SimpleConstraintResolver( options ), options ) { }
+
+    // intentionally hiding IInlineConstraintResolver from public signature until ASP.NET Core fixes their bug
+    // BUG: https://github.com/dotnet/aspnetcore/issues/41773
+    internal VersionedApiDescriptionProvider(
+        ISunsetPolicyManager sunsetPolicyManager,
+        IModelMetadataProvider modelMetadataProvider,
+        IInlineConstraintResolver constraintResolver,
+        IOptions<ApiExplorerOptions> options )
     {
         SunsetPolicyManager = sunsetPolicyManager;
         ModelMetadataProvider = modelMetadataProvider;
+        this.constraintResolver = constraintResolver;
         this.options = options;
     }
 
@@ -83,6 +96,7 @@ protected virtual void PopulateApiVersionParameters( ApiDescription apiDescripti
         var parameterSource = Options.ApiVersionParameterSource;
         var context = new ApiVersionParameterDescriptionContext( apiDescription, apiVersion, ModelMetadata, Options );
 
+        context.ConstraintResolver = constraintResolver;
         parameterSource.AddParameters( context );
     }
 
@@ -247,4 +261,21 @@ private IEnumerable<ApiVersion> FlattenApiVersions( IList<ApiDescription> descri
 
         return versions;
     }
+
+    private sealed class SimpleConstraintResolver : IInlineConstraintResolver
+    {
+        private readonly IOptions<ApiExplorerOptions> options;
+
+        internal SimpleConstraintResolver( IOptions<ApiExplorerOptions> options ) => this.options = options;
+
+        public IRouteConstraint? ResolveConstraint( string inlineConstraint )
+        {
+            if ( options.Value.RouteConstraintName == inlineConstraint )
+            {
+                return new ApiVersionRouteConstraint();
+            }
+
+            return default;
+        }
+    }
 }