FROZEN: Add build-time OpenAPI generation doc

aspnetcore/fundamentals/openapi/aspnetcore-openapi.md

@@ -8,6 +8,8 @@ ms.custom: mvc
 ms.date: 5/22/2024
 uid: fundamentals/openapi/aspnetcore-openapi
 ---
+<!-- backup writer.sms.author: tdykstra and rick-anderson -->
+
 # Work with OpenAPI documents
 
 :::moniker range=">= aspnetcore-9.0"
@@ -67,7 +69,7 @@ The following code:
 * Adds OpenAPI services.
 * Enables the endpoint for viewing the OpenAPI document in JSON format.
 
-[!code-csharp[](~/fundamentals/minimal-apis/9.0-samples/WebMinOpenApi/Program.cs?name=snippet_first&highlight=3,7)]
+[!code-csharp[](~/fundamentals/openapi/samples/9.x/WebMinOpenApi/Program.cs?name=snippet_first&highlight=3,7)]
 
 Launch the app and navigate to `https://localhost:<port>/openapi/v1.json` to view the generated OpenAPI document.
 
@@ -400,13 +402,13 @@ Because the OpenAPI document is served via a route handler endpoint, any customi
 
 The OpenAPI endpoint  doesn't enable any authorization checks by default. However, it's possible to limit access to the OpenAPI document. For example, in the following code, access to the OpenAPI document is limited to those with the `tester` role:
 
-[!code-csharp[](~/fundamentals/minimal-apis/9.0-samples/WebMinOpenApi/Program.cs?name=snippet_mapopenapiwithauth)]
+[!code-csharp[](~/fundamentals/openapi/samples/9.x/WebMinOpenApi/Program.cs?name=snippet_mapopenapiwithauth)]
 
 #### Cache generated OpenAPI document
 
 The OpenAPI document is regenerated every time a request to the OpenAPI endpoint is sent. Regeneration enables transformers to incorporate dynamic application state into their operation. For example, regenerating a request with details of the HTTP context. When applicable, the OpenAPI document can be cached to avoid executing the document generation pipeline on each HTTP request.
 
-[!code-csharp[](~/fundamentals/minimal-apis/9.0-samples/WebMinOpenApi/Program.cs?name=snippet_mapopenapiwithcaching)]
+[!code-csharp[](~/fundamentals/openapi/samples/9.x/WebMinOpenApi/Program.cs?name=snippet_mapopenapiwithcaching)]
 
 <a name="transformers"></a>
 
@@ -427,20 +429,20 @@ Transformers fall into two categories:
 * Document transformers have access to the entire OpenAPI document. These can be used to make global modifications to the document.
 * Operation transformers apply to each individual operation. Each individual operation is a combination of path and HTTP method. These can be used to modify parameters or responses on endpoints.
 
-Transformers can be registered onto the document via the `UseTransformer` call on the `OpenApiOptions` object. The following snippet shows different ways to register transformers onto the document:
+Transformers can be registered onto the document via the `AddDocumentTransformer` call on the `OpenApiOptions` object. The following snippet shows different ways to register transformers onto the document:
 
 * Register a document transformer using a delegate.
 * Register a document transformer using an instance of `IOpenApiDocumentTransformer`.
 * Register a document transformer using a DI-activated `IOpenApiDocumentTransformer`.
 * Register an operation transformer using a delegate.
 
-[!code-csharp[](~/fundamentals/minimal-apis/9.0-samples/WebMinOpenApi/Program.cs?name=snippet_transUse&highlight=8-13)]
+[!code-csharp[](~/fundamentals/openapi/samples/9.x/WebMinOpenApi/Program.cs?name=snippet_transUse&highlight=8-13)]
 
 ### Execution order for transformers
 
 Transformers execute in first-in first-out order based on registration. In the following snippet, the document transformer has access to the modifications made by the operation transformer:
 
-[!code-csharp[](~/fundamentals/minimal-apis/9.0-samples/WebMinOpenApi/Program.cs?name=snippet_transInOut&highlight=3-9)]
+[!code-csharp[](~/fundamentals/openapi/samples/9.x/WebMinOpenApi/Program.cs?name=snippet_transInOut&highlight=3-9)]
 
 ### Use document transformers
 
@@ -452,18 +454,18 @@ Document transformers have access to a context object that includes:
 
 Document transformers also can mutate the OpenAPI document that is generated. The following example demonstrates a document transformer that adds some information about the API to the OpenAPI document.
 
-[!code-csharp[](~/fundamentals/minimal-apis/9.0-samples/WebMinOpenApi/Program.cs?name=snippet_documenttransformer1)]
+[!code-csharp[](~/fundamentals/openapi/samples/9.x/WebMinOpenApi/Program.cs?name=snippet_documenttransformer1)]
 
 Service-activated document transformers can utilize instances from DI to modify the app. The following sample demonstrates a document transformer that uses the `IAuthenticationSchemeProvider` service from the authentication layer. It checks if any JWT bearer-related schemes are registered in the app and adds them to the OpenAPI document's top level:
 
-[!code-csharp[](~/fundamentals/minimal-apis/9.0-samples/WebMinOpenApi/Program.cs?name=snippet_documenttransformer2)]
+[!code-csharp[](~/fundamentals/openapi/samples/9.x/WebMinOpenApi/Program.cs?name=snippet_documenttransformer2)]
 
 Document transformers are unique to the document instance they're associated with. In the following example, a transformer:
 
 * Registers authentication-related requirements to the `internal` document.
 * Leaves the `public` document unmodified.
 
-[!code-csharp[](~/fundamentals/minimal-apis/9.0-samples/WebMinOpenApi/Program.cs?name=snippet_multidoc_operationtransformer1)]
+[!code-csharp[](~/fundamentals/openapi/samples/9.x/WebMinOpenApi/Program.cs?name=snippet_multidoc_operationtransformer1)]
 
 ### Use operation transformers
 
@@ -480,7 +482,7 @@ Operation transformers have access to a context object which contains:
 
 For example, the following operation transformer adds `500` as a response status code supported by all operations in the document.
 
-[!code-csharp[](~/fundamentals/minimal-apis/9.0-samples/WebMinOpenApi/Program.cs?name=snippet_operationtransformer1)]
+[!code-csharp[](~/fundamentals/openapi/samples/9.x/WebMinOpenApi/Program.cs?name=snippet_operationtransformer1)]
 
 ## Using the generated OpenAPI document
 
@@ -494,13 +496,13 @@ The `Swashbuckle.AspNetCore.SwaggerUi` package provides a bundle of Swagger UI's
 
 Enable the swagger-ui middleware with a reference to the OpenAPI route registered earlier. To limit information disclosure and security vulnerability, ***only enable Swagger UI in development environments.***
 
-[!code-csharp[](~/fundamentals/minimal-apis/9.0-samples/WebMinOpenApi/Program.cs?name=snippet_swaggerui)]
+[!code-csharp[](~/fundamentals/openapi/samples/9.x/WebMinOpenApi/Program.cs?name=snippet_swaggerui)]
 
 ### Using Scalar for interactive API documentation
 
 [Scalar](https://scalar.com/) is an open-source interactive document UI for OpenAPI. Scalar can integrate with the OpenAPI endpoint provided by ASP.NET Core. To configure Scalar, install the `Scalar.AspNetCore` package.
 
-[!code-csharp[](~/fundamentals/minimal-apis/9.0-samples/WebMinOpenApi/Program.cs?name=snippet_openapiwithscalar)]
+[!code-csharp[](~/fundamentals/openapi/samples/9.x/WebMinOpenApi/Program.cs?name=snippet_openapiwithscalar)]
 
 ### Lint generated OpenAPI documents with Spectral
 

aspnetcore/fundamentals/openapi/buildtime-openapi.md

@@ -0,0 +1,131 @@
+---
+title: Generate OpenAPI documents at build time
+author: captainsafia
+description: Learn how to generate OpenAPI documents in your application's build step
+ms.author: safia
+monikerRange: '>= aspnetcore-9.0'
+ms.custom: mvc
+ms.date: 8/13/2024
+uid: fundamentals/openapi/buildtime-openapi
+---
+<!-- Per this comment by Mike, Question for @captainsafia: This doc currently says aspnetcore-6.0 and later. Should we make this just 9.0 and later, since 8.0 and earlier involve Swashbuckle or NSwag generating the doc?
+I made it 9.0
+https://github.com/dotnet/AspNetCore.Docs/pull/33361#discussion_r1778546753 -->
+<!-- backup writer.sms.author: tdykstra and rick-anderson -->
+
+# Generate OpenAPI documents at build-time
+
+In typical web apps, OpenAPI documents are generated at run-time and served via an HTTP request to the app server.
+
+Generating OpenAPI documentation during the app's build step can be useful for documentation that is:
+
+- Committed into source control.
+- Used for spec-based integration testing.
+- Served statically from the web server.
+
+To add support for generating OpenAPI documents at build time, install the [`Microsoft.Extensions.ApiDescription.Server`](https://www.nuget.org/packages/Microsoft.Extensions.ApiDescription.Server) NuGet package:
+
+### [Visual Studio](#tab/visual-studio)
+
+Run the following command from the **Package Manager Console**:
+
+ ```powershell
+ Install-Package Microsoft.Extensions.ApiDescription.Server -IncludePrerelease
+```
+
+### [.NET CLI](#tab/net-cli)
+
+Run the following command in the directory that contains the project file:
+
+```dotnetcli
+dotnet add package Microsoft.Extensions.ApiDescription.Server --prerelease
+```
+
+---
+
+The `Microsoft.Extensions.ApiDescription.Server` package automatically generates the Open API document(s) associated with the app during build and places them in the app's `obj` directory:
+
+Consider a template created API app named `MyTestApi`:
+
+### [Visual Studio](#tab/visual-studio)
+
+The Output tab in Visual Studio when building the app includes information similar to the following:
+
+```text
+1>Generating document named 'v1'.
+1>Writing document named 'v1' to 'MyProjectPath/obj/MyTestApi.json'.
+```
+
+### [.NET CLI](#tab/net-cli)
+
+The following commands build the app and display the generated OpenAPI document:
+
+```cli
+$ dotnet build
+$ cat obj/MyTestApi.json
+```
+
+---
+
+The generated `obj/{MyProjectName}.json` file contains the [OpenAPI version, title,  endpoints, and more](https://learn.openapis.org/specification/structure.html). The first few lines of `obj/MyTestApi.json` file:
+
+:::code language="json" source="~/fundamentals/openapi/samples/9.x/BuildTime/csproj/MyTestApi.json" range="1-15" highlight="4-5":::
+
+## Customize build-time document generation
+
+Build-time document generation can be customized with properties added to the project file. [dotnet](/dotnet/core/tools/) parses the `ApiDescription.Server` properties in the project file and provides the property and values as arguments to the build-time document generator. The following properties are available and explained in the following sections:
+
+:::code language="xml" source="~/fundamentals/openapi/samples/9.x/BuildTime/csproj/MyTestApi.csproj.php" id="snippet_all" highlight="2-4":::
+
+### Modify the output directory of the generated Open API file
+
+By default, the generated OpenAPI document is generated in the `obj` directory. The value of the `OpenApiDocumentsDirectory` property:
+
+* Sets the location of the generated file.
+* Is resolved relative to the project file.
+
+The following example generates the OpenAPI document in the same directory as the project file:
+
+:::code language="xml" source="~/fundamentals/openapi/samples/9.x/BuildTime/csproj/MyTestApi.csproj.php" id="snippet_1" highlight="2":::
+
+In the following example, the OpenAPI document is generated in the `MyOpenApiDocs` directory, which is a sibling directory to the project directory:
+
+:::code language="xml" source="~/fundamentals/openapi/samples/9.x/BuildTime/csproj/MyTestApi.csproj.php" id="snippet2" highlight="2":::
+
+### Modify the output file name
+
+By default, the generated OpenAPI document has the same name as the app's project file. To modify the name of the generated file, set the `--file-name` argument in the `OpenApiGenerateDocumentsOptions` property:
+
+:::code language="xml" source="~/fundamentals/openapi/samples/9.x/BuildTime/csproj/MyTestApi.csproj.php" id="snippet_file_name" highlight="2":::
+
+The preceding markup configures creation of the `obj/my-open-api.json` file.
+
+### Select the OpenAPI document to generate
+
+Some apps may be configured to generate multiple OpenAPI documents, for example:
+
+* For different versions of an API.
+* To distinguish between public and internal APIs.
+
+By default, the build-time document generator creates files for all documents that are configured in an app. To generate for a single document only, set the `--document-name` argument in the `OpenApiGenerateDocumentsOptions` property:
+
+:::code language="xml" source="~/fundamentals/openapi/samples/9.x/BuildTime/csproj/MyTestApi.csproj.php" id="snippet_doc_name":::
+
+<!-- comment out this section until it's sorted 
+## Customize run-time behavior during build-time document generation
+
+OpenAPI document generation at build-time works by starting the app’s entry point with a temporary background server. This approach is necessary to produce accurate OpenAPI documents, as not all information can be statically analyzed. When the app’s entry point is invoked, any logic in the app’s startup is executed, including code that injects services into the DI container or reads from configuration.
+
+In some scenarios, it's important to restrict certain code paths when the app's entry point is invoked during build-time document generation. These scenarios include:
+
+- Not reading from specific configuration strings.
+- Not registering database-related services.
+
+To prevent these code paths from being invoked by the build-time generation pipeline, they can be conditioned behind a check of the entry assembly:
+
+:::code language="csharp" source="~/fundamentals/openapi/samples/9.x/BuildTime/Skip.cs" id="snippet_1" highlight="7-12":::
+-->
+
+## OpenAPI document cleanup
+
+The generated OpenAPI documents are not cleaned up by `dotnet clean` or **Build > Clean Solution** in Visual Studio. To remove the generated OpenAPI documents, delete the `obj` directory or the directory specified by the `OpenApiDocumentsDirectory` property.

aspnetcore/fundamentals/openapi/samples/9.x/BuildTime/MyTestApi.csproj

@@ -0,0 +1,25 @@
+<Project Sdk="Microsoft.NET.Sdk.Web">
+
+  <PropertyGroup>
+    <TargetFramework>net9.0</TargetFramework>
+    <Nullable>enable</Nullable>
+    <ImplicitUsings>enable</ImplicitUsings>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Microsoft.AspNetCore.OpenApi" Version="9.0.0-rc.1.24412.15" />
+    <PackageReference Include="Microsoft.Extensions.ApiDescription.Server" Version="9.0.0-rc.2.24420.12">
+      <PrivateAssets>all</PrivateAssets>
+      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
+    </PackageReference>
+  </ItemGroup>
+
+  <PropertyGroup>
+    <DocNameV2>true</DocNameV2>
+  </PropertyGroup>
+
+  <PropertyGroup Condition=" '$(DocNameV2)' == 'true' ">
+    <OpenApiGenerateDocumentsOptions>--document-name v2</OpenApiGenerateDocumentsOptions>
+  </PropertyGroup>
+
+</Project>

aspnetcore/fundamentals/openapi/samples/9.x/BuildTime/MyTestApi.http

@@ -0,0 +1,6 @@
+@MyTestApi_HostAddress = http://localhost:5276
+
+GET {{MyTestApi_HostAddress}}/weatherforecast/
+Accept: application/json
+
+###

aspnetcore/fundamentals/openapi/samples/9.x/BuildTime/Program.cs

@@ -0,0 +1,53 @@
+var builder = WebApplication.CreateBuilder(args);
+
+builder.Services.AddOpenApi();
+builder.Services.AddOpenApi("v2");
+
+var app = builder.Build();
+
+if (app.Environment.IsDevelopment())
+{
+    app.MapOpenApi();
+}
+
+app.UseHttpsRedirection();
+
+var summaries = new[]
+{
+    "Freezing", "Bracing", "Chilly", "Cool", "Mild", "Warm", "Balmy", "Hot", "Sweltering", "Scorching"
+};
+
+app.MapGet("/weatherforecast", () =>
+{
+    var forecast = Enumerable.Range(1, 5).Select(index =>
+        new WeatherForecast
+        (
+            DateOnly.FromDateTime(DateTime.Now.AddDays(index)),
+            Random.Shared.Next(-20, 55),
+            summaries[Random.Shared.Next(summaries.Length)]
+        ))
+        .ToArray();
+    return forecast;
+})
+.WithName("GetWeatherForecast");
+
+app.MapGet("/v2/weatherforecast", (HttpContext httpContext) =>
+{
+    var forecast = Enumerable.Range(1, 5).Select(index =>
+        new WeatherForecast
+        (
+            DateOnly.FromDateTime(DateTime.Now.AddDays(index)),
+            Random.Shared.Next(-20, 55),
+            summaries[Random.Shared.Next(summaries.Length)]
+        ))
+        .ToArray();
+    return forecast;
+})
+.WithGroupName("v2");
+
+app.Run();
+
+record WeatherForecast(DateOnly Date, int TemperatureC, string? Summary)
+{
+    public int TemperatureF => 32 + (int)(TemperatureC / 0.5556);
+}

aspnetcore/fundamentals/openapi/samples/9.x/BuildTime/Skip.cs

@@ -0,0 +1,34 @@
+#if NEVER
+// <snippet_1>
+using ControllerApi.Data;
+using Microsoft.EntityFrameworkCore;
+using System.Reflection;
+
+var builder = WebApplication.CreateBuilder(args);
+
+if (Assembly.GetEntryAssembly()?.GetName().Name != "MyTestApi")
+{
+    builder.Services.AddDbContext<ControllerApiContext>(options =>
+        options.UseSqlServer(builder.Configuration.GetConnectionString("ControllerApiContext")
+        ?? throw new InvalidOperationException("Connection string 'ControllerApiContext' not found.")));
+}
+
+builder.Services.AddControllers();
+builder.Services.AddOpenApi();
+
+var app = builder.Build();
+
+if (app.Environment.IsDevelopment())
+{
+    app.MapOpenApi();
+}
+
+app.UseHttpsRedirection();
+
+app.UseAuthorization();
+
+app.MapControllers();
+
+app.Run();
+// </snippet_1>
+#endif

aspnetcore/fundamentals/openapi/samples/9.x/BuildTime/csproj/MyTestApi.csproj.php

@@ -0,0 +1,39 @@
+<!-- 
+    This file is needed to contain snippets and provides a convenient
+    location to copy/paste the <PropertyGroup> into the .csproj file.
+    The dash dash sequence is an illegal string in an XML comment and
+    results in the error: An XML comment cannot contain --.
+    
+    That's why this is stored as an HTML file.
+ -->
+
+<!-- <snippet_file_name> -->
+<PropertyGroup>
+    <OpenApiGenerateDocumentsOptions>--file-name my-open-api</OpenApiGenerateDocumentsOptions>
+</PropertyGroup>
+<!-- </snippet_file_name> -->
+
+<!--<snippet_1>-->
+<PropertyGroup>
+    <OpenApiDocumentsDirectory>.</OpenApiDocumentsDirectory>
+</PropertyGroup>
+<!--</snippet_1>-->
+<!--<snippet2>-->
+<PropertyGroup>
+    <OpenApiDocumentsDirectory>../MyOpenApiDocs</OpenApiDocumentsDirectory>
+</PropertyGroup>
+<!--</snippet2>-->
+
+<!--<snippet_doc_name>-->
+<PropertyGroup>
+    <OpenApiGenerateDocumentsOptions>--document-name v2</OpenApiGenerateDocumentsOptions>
+</PropertyGroup>
+<!--</snippet_doc_name>-->
+
+<!-- <snippet_all> -->
+<PropertyGroup>
+    <OpenApiDocumentsDirectory>.</OpenApiDocumentsDirectory>
+    <OpenApiGenerateDocumentsOptions>--file-name my-open-api</OpenApiGenerateDocumentsOptions>
+    <OpenApiGenerateDocumentsOptions>--document-name v2</OpenApiGenerateDocumentsOptions>
+</PropertyGroup>
+<!-- </snippet_all> -->