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Use Argu to access .NET Core hosted configuration (appSettings.json)

Configure Argu to read from hosted Microsoft.Extensions.Configuration and pass a ParseResult<'T> through dependency injection. This allows you to combine Argu's full-featured command-line handling and strong typing with M.E.C's multiple sources (appSettings..json, environment variables, etc).

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open Microsoft.Extensions.Configuration
open Microsoft.Extensions.DependencyInjection
open Argu

type HostedConfigurationReader(config: IConfiguration) =
    interface IConfigurationReader with
        member this.GetValue(k) = config.[k]
        member this.Name = ".NET Core hosted configuration"

type IServiceCollection with
    member this.AddArgu<'T when 'T : not struct and 'T :> IArgParserTemplate>(configure: IConfigurationReader -> ParseResults<'T>) =
        this.AddSingleton<IConfigurationReader, HostedConfigurationReader>()
        this.AddSingleton<ParseResults<'T>>(fun services ->
            services.GetRequiredService<IConfiguration>()
            |> HostedConfigurationReader
            |> configure)

    member this.AddArgu<'T when 'T : not struct and 'T :> IArgParserTemplate>() =
        this.AddArgu<'T>(fun config -> ArgumentParser.Create<'T>().Parse(configurationReader = config))

//// Example use:

type Args =
    // Passed as --file XXX on the CLI
    // or { "file": XXX } in appSettings.json
    // or FILE environment variable
    | File of string
    // Passed as --url on the CLI
    // or { "myService": { "url": XXX } } in appSettings.json
    // or MYSERVICE__URL envirenment variable
    | [<CustomAppSettings "myService:url">] Url of string

    interface IArgParserTemplate with
        member this.Usage =
            match this with
            | File _ -> "a file."
            | Url _ -> "the url of my service."

// Service using it:
type MyService(args: ParseResults<Args>) =
    let file = args.GetResult Args.File
    let url = args.GetResult Args.Url

// App startup config:
type Startup() =
    member this.ConfigureServices(services: IServiceCollection) =
        services.AddArgu<Args>()
        |> ignore

namespace Microsoft

Multiple items
type HostedConfigurationReader =
  interface obj
  new : config:obj -> HostedConfigurationReader
  override GetValue : k:'a -> 'b
  override Name : string

Full name: Script.HostedConfigurationReader

--------------------
new : config:obj -> HostedConfigurationReader

val config : obj

val this : HostedConfigurationReader

override HostedConfigurationReader.GetValue : k:'a -> 'b

Full name: Script.HostedConfigurationReader.GetValue

val k : 'a

override HostedConfigurationReader.Name : string

Full name: Script.HostedConfigurationReader.Name

val not : value:bool -> bool

Full name: Microsoft.FSharp.Core.Operators.not

type Args =
  | File of string
  | Url of string
  interface obj
  override Usage : string

Full name: Script.Args

union case Args.File: string -> Args

Multiple items
val string : value:'T -> string

Full name: Microsoft.FSharp.Core.Operators.string

--------------------
type string = System.String

Full name: Microsoft.FSharp.Core.string

union case Args.Url: string -> Args

val this : Args

override Args.Usage : string

Full name: Script.Args.Usage

Multiple items
type MyService =
new : args:obj -> MyService

Full name: Script.MyService

--------------------
new : args:obj -> MyService

val args : obj

val file : obj

val url : obj

Multiple items
type Startup =
new : unit -> Startup
member ConfigureServices : services:'a -> unit

Full name: Script.Startup

--------------------
new : unit -> Startup

val this : Startup

member Startup.ConfigureServices : services:'a -> unit

Full name: Script.Startup.ConfigureServices

val services : 'a

val ignore : value:'T -> unit

Full name: Microsoft.FSharp.Core.Operators.ignore

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More information

Link:	http://fssnip.net/7XO
Posted:	4 years ago
Author:	Loïc Denuzière
Tags:	argument parsing , asp.net , configuration