OpenApiGenerateDocumentsOnBuild not working with .net 6 minimal api ?

[GMouron]

Hello,

I am trying to generate the swagger docs on build with <OpenApiGenerateDocumentsOnBuild>true</OpenApiGenerateDocumentsOnBuild> but I experience the following error :
No method 'BuildWebHost', 'CreateHostBuilder' or 'CreateWebHostBuilder' found in type 'Program' with expected signatures.
Version used : 6.2.3
You can find a minimum repro here :
LuccaSA/minmal-api-samples#2
This repo is a fork of https://github.com/Minimal-APIs/samples made by a microsoftie where they describe how to add open api support (https://minimal-apis.github.io/quickstart/openapi.html)
In the first PR (LuccaSA/minmal-api-samples#1), I added the nuget and the necessary code following the tutorial, and it does indeed work at runtime.

When I inspect the dll, those methods do not exist, so this is "right".
(Note : I experienced the same problem on an internal project also setup as minmal api)

If it's not fixable, would there be a workaround possible ? The doc should probably be updated to mention this case (I could take care of that) ?

Thank you.

[crhairr]

I'm seeing the same problem with .NET 6.0 minimal APIs. My guess is that this is caused by this line and declared as a dependency here. It appears that Microsoft.Extension.ApiDescription.Server version 3.0.0 doesn't support minimal apis. I manually installed 6.0.2 and ran the included dotnet-getdocument tool on my web api assembly, and it correctly generated the expected json output file.

Update: adding a direct package reference to Microsoft.Extensions.ApiDescription.Server version 6.0.2 to my web api project allows the build to succeed. It just takes 2 builds for MSBuild to fully replace the reference.

[GMouron]

Yes, it solved my problem !
I know have a different problem, there is no endpoint listed in the file but I don't think it's linked

[agilenut]

Same problem.

Also, I'd like to have a better way to override the host. I know that we can use SwaggerHostFactory or SwaggerWebHostFactory but, now with minimal apis, there's no Startup.cs, and I'd rather not add it. So, I can't use the web host builder to add everything. Ideally, I could use the existing Program.cs but override a couple of things like the app configuration block and logging setup.

[SirSeven]

We experienced the same problem when switching our "controller"-based APIs to the minimal-API approach. While NSwag and SwashBuckle can generate the swagger.json just fine. dotnet-getdocument always produces an empty document. Did any of you already solve this problem?

[nielsheeren]

We experienced the same problem when switching our "controller"-based APIs to the minimal-API approach. While NSwag and SwashBuckle can generate the swagger.json just fine. dotnet-getdocument always produces an empty document. Did any of you already solve this problem?

I had had the same problem and had to fix it by manually setting the ApplicationName in WebApplicationOptions like this:

public class SwaggerHostFactory
{
    public static IHost CreateHost()
    {
        var options = new WebApplicationOptions() { ApplicationName = typeof(SwaggerHostFactory).Assembly.FullName };
        var builder = WebApplication.CreateBuilder(options);
        ...
    }
}

[github-actions]

This issue is stale because it has been open for 60 days with no activity. It will be automatically closed in 14 days if no further updates are made.

[martincostello]

Duplicate of #2290.