Use config within application CE

[yurotor]

Currently, if i add a use_config operation to the application CE, i will be able to access the config through HttpContext in any controller. But what if i need the config data in the application itself? For example, when i use the service_config operation to integrate identity server authentication, i need to load the settings from an appSettings.json file. Am i missing something or is it not implemented?

[baronfel]

I agree that it should be possible to provide the current configuration at application CE usage. This is in line with the various lifecycle hooks that aspnetcore provides currently. They typically allow for DI of the IConfiguration type into the Startup type used, and our analogue would be providing a way to extract out the IConfiguration from the current app CE.

I see a couple options:

• a new CE operation could be made that would provide access to the IConfiguration

  • I don't recommend this because currently the webhostbuilder (which contains the IConfiguration we'd be returning) isn't created until the Run CE method is invoked, so this would be a large refactor

• current CE operations that could make use of IConfiguration could have overloads added that would provide the IConfiguration

  • this is non-breaking
  • users can opt into IConfiguration if they need it
  • still follows the existing model because the IConfiguration can be fetched once during Run and fed into the user-configured lambdas as necessary.

[yurotor]

Here is how i finally solved it:

Add a host_config operation to your app CE to read from settings file(s): host_config (fun (webHost:IWebHostBuilder) = webHost.ConfigureAppConfiguration(fun ctx builder -> builder.AddJsonFile(sprintf "appSettings.%s.json" ctx.HostingEnvironment.EnvironmentName) |> ignore ))

Access the configuration from within any function in the app CE like this: fun (services:IServiceCollection) = let config = services .BuildServiceProvider() .GetService<IConfiguration>() .GetSection("MySettingsSection") .Get<MySettings>() //do whatever needed with the config

Where the MySettings type is marked with the CLIMutable attribute. If you need to access the MySettings within HTTP requests, then first register it using the service_config operation in the app CE like this: service_config (fun (services:IServiceCollection) = let cfg = services .BuildServiceProvider() .GetService<IConfiguration>() .GetSection("MySettingsSection") services.Configure<MySettings>(cfg)

Then, add a pipe_through operation to your router CE like this: pipe_through (fun _ : HttpHandler = fun next ctx -> let cfg = ctx.RequestServices.GetRequiredService<IOptions<MySettings>>().Value //do something with the config and return an HttpHandler)

[MarneeDear]

Thank you. I ended up using this in a custom ApplicationBuilder method I wrote to handle CAS authentication. This made it so I didn't have to hardcode the settings. It looks like this:

    [<CustomOperation("use_cas")>]
    member __.UseCasAuthentication(state: ApplicationState, webAuthSettingKey) =
        let middleware (app : IApplicationBuilder) =
            app.UseAuthentication() 

        let service (s : IServiceCollection) =
            let config = s.BuildServiceProvider()
                            .GetService<IConfiguration>()         
                            .GetSection(webAuthSettingKey) 
            let c = s.AddAuthentication(fun cfg ->
                cfg.DefaultScheme <- CookieAuthenticationDefaults.AuthenticationScheme
                cfg.DefaultChallengeScheme <- "CAS"
                )
            c.AddCAS(fun o -> 
                o.CasServerUrlBase <- config.Value //["WebAuth:Url"]
                o.SignInScheme <- CookieAuthenticationDefaults.AuthenticationScheme
                )
            |> ignore
            s

        { state with
            ServicesConfig = service::state.ServicesConfig
            AppConfigs = middleware::state.AppConfigs
        }

[Krzysztof-Cieslak]

Suggestions from @yurotor are correct - in Saturn 0.14 we will add some helpers functions to make this user friendly