Upgrade to Microsoft.OpenApi 2.x and support OpenAPI v3.1

eng/Versions.props

@@ -328,8 +328,8 @@
     <XunitExtensibilityExecutionVersion>$(XunitVersion)</XunitExtensibilityExecutionVersion>
     <XUnitRunnerVisualStudioVersion>2.8.2</XUnitRunnerVisualStudioVersion>
     <MicrosoftDataSqlClientVersion>5.2.2</MicrosoftDataSqlClientVersion>
-    <MicrosoftOpenApiVersion>1.6.17</MicrosoftOpenApiVersion>
-    <MicrosoftOpenApiReadersVersion>1.6.17</MicrosoftOpenApiReadersVersion>
+    <MicrosoftOpenApiVersion>2.0.0-preview2</MicrosoftOpenApiVersion>
+    <MicrosoftOpenApiReadersVersion>2.0.0-preview2</MicrosoftOpenApiReadersVersion>
     <!-- dotnet tool versions (see also auto-updated DotnetEfVersion property). -->
     <DotnetDumpVersion>6.0.322601</DotnetDumpVersion>
     <DotnetServeVersion>1.10.93</DotnetServeVersion>

eng/testing/linker/project.csproj.template

@@ -16,6 +16,8 @@
     <InterceptorsPreviewNamespaces>$(InterceptorsPreviewNamespaces);Microsoft.AspNetCore.Http.Generated</InterceptorsPreviewNamespaces>
     <!-- Ensure individual warnings are shown when publishing -->
     <TrimmerSingleWarn>false</TrimmerSingleWarn>
+    <!-- But ignore the single warn files marked below to suppress their known warnings. -->
+    <NoWarn>$(NoWarn);IL2104;IL3053</NoWarn>
     {AdditionalProperties}
   </PropertyGroup>
 
@@ -27,4 +29,19 @@
     {AdditionalProjectReferences}
   </ItemGroup>
 
+  <!-- Single warn the following assemblies, which have known warnings, so the warnings can be suppressed for now.
+  Remove this (and the above NoWarn IL2104) once  https://github.com/microsoft/OpenAPI.NET/issues/1875 is addressed. -->
+  <Target Name="ConfigureTrimming"
+          BeforeTargets="PrepareForILLink">
+    <ItemGroup>
+      <IlcArg Include="--singlewarnassembly:Microsoft.OpenApi" />
+    </ItemGroup>
+    <ItemGroup>
+      <ManagedAssemblyToLink Condition="'%(Filename)' == 'Microsoft.OpenApi'">
+        <IsTrimmable>true</IsTrimmable>
+        <TrimmerSingleWarn>true</TrimmerSingleWarn>
+      </ManagedAssemblyToLink>
+    </ItemGroup>
+  </Target>
+
 </Project>

src/OpenApi/perf/Microbenchmarks/TransformersBenchmark.cs

@@ -104,11 +104,11 @@ public void SchemaTransformer_Setup()
             {
                 if (context.JsonTypeInfo.Type == typeof(Todo) && context.ParameterDescription != null)
                 {
-                    schema.Extensions["x-my-extension"] = new OpenApiString(context.ParameterDescription.Name);
+                    schema.Extensions["x-my-extension"] = new OpenApiAny(context.ParameterDescription.Name);
                 }
                 else
                 {
-                    schema.Extensions["x-my-extension"] = new OpenApiString("response");
+                    schema.Extensions["x-my-extension"] = new OpenApiAny("response");
                 }
                 return Task.CompletedTask;
             });
@@ -177,11 +177,11 @@ public Task TransformAsync(OpenApiSchema schema, OpenApiSchemaTransformerContext
         {
             if (context.JsonTypeInfo.Type == typeof(Todo) && context.ParameterDescription != null)
             {
-                schema.Extensions["x-my-extension"] = new OpenApiString(context.ParameterDescription.Name);
+                schema.Extensions["x-my-extension"] = new OpenApiAny(context.ParameterDescription.Name);
             }
             else
             {
-                schema.Extensions["x-my-extension"] = new OpenApiString("response");
+                schema.Extensions["x-my-extension"] = new OpenApiAny("response");
             }
             return Task.CompletedTask;
         }

src/OpenApi/sample/Transformers/AddExternalDocsTransformer.cs

@@ -29,7 +29,7 @@ public Task TransformAsync(OpenApiSchema schema, OpenApiSchemaTransformerContext
     {
         if (Uri.TryCreate(configuration["DocumentationBaseUrl"], UriKind.Absolute, out var baseUri))
         {
-            var url = new Uri(baseUri, $"/api/docs/schemas/{Uri.EscapeDataString(schema.Type)}");
+            var url = new Uri(baseUri, $"/api/docs/schemas/{Uri.EscapeDataString(schema.Type.ToString()!)}");
 
             schema.ExternalDocs = new OpenApiExternalDocs
             {

src/OpenApi/sample/Transformers/OperationTransformers.cs

@@ -2,7 +2,6 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using Microsoft.AspNetCore.OpenApi;
-using Microsoft.OpenApi.Any;
 using Microsoft.OpenApi.Extensions;
 using Microsoft.OpenApi.Models;
 
@@ -15,7 +14,7 @@ public static OpenApiOptions AddHeader(this OpenApiOptions options, string heade
         return options.AddOperationTransformer((operation, context, cancellationToken) =>
         {
             var schema = OpenApiTypeMapper.MapTypeToOpenApiPrimitiveType(typeof(string));
-            schema.Default = new OpenApiString(defaultValue);
+            schema.Default = defaultValue;
             operation.Parameters ??= [];
             operation.Parameters.Add(new OpenApiParameter
             {