implement ParseResult.TryGetSubCommand

Author: eiriktsarpalis

src/Argu/ParseResult.fs

@@ -194,6 +194,18 @@ type ParseResult<'Template when 'Template :> IArgParserTemplate>
     member r.IterResult (expr : Expr<'Field -> 'Template>, iterator : 'Field -> unit, ?source) : unit =
         expr |> tryGetResult source |> Option.iter (parseResult iterator)
 
+    /// <summary>
+    ///     Attempts to recover the subcommand parameter from the results,
+    ///     if once has been specified.
+    /// </summary>
+    member r.TryGetSubCommand() : 'Template option =
+        results.Cases 
+        |> Seq.concat 
+        |> Seq.tryPick(fun c -> 
+            if c.ArgInfo.Type = ArgumentType.SubCommand then
+                Some(c.Value :?> 'Template)
+            else None)
+
     override r.ToString() = sprintf "%A" (r.GetAllResults())
 
     // used by StructuredFormatDisplay attribute

tests/Argu.Tests/Argu.Tests.fsproj

@@ -186,7 +186,7 @@
       <ItemGroup>
         <Reference Include="FSharp.Core">
           <HintPath>..\..\packages\FSharp.Core\lib\net40\FSharp.Core.dll</HintPath>
-          <Private>True</Private>
+          <Private>False</Private>
           <Paket>True</Paket>
         </Reference>
       </ItemGroup>

tests/Argu.Tests/Tests.fs

@@ -229,13 +229,15 @@ module ``Argu Tests`` =
         let args = [|"push"; "--remote" ; "origin" ; "--branch" ; "master"|]
         let results = parser.ParseCommandLine(args, ignoreMissing = true)
         let nested = results.GetResult <@ Push @>
+        test <@ match results.TryGetSubCommand() with Some (Push _) -> true | _ -> false @>
         test <@ nested.GetAllResults() = [Remote "origin" ; Branch "master"] @>
 
     [<Fact>]
     let ``Simple subcommand parsing 2`` () =
         let args = [|"clean"; "-fdx"|]
         let results = parser.ParseCommandLine(args, ignoreMissing = true)
         let nested = results.GetResult <@ Clean @>
+        test <@ match results.TryGetSubCommand() with Some (Clean _) -> true | _ -> false @>
         test <@ nested.GetAllResults() = [F; D; X] @>
 
     [<Fact>]