Compile typed command runners

execute.go

@@ -33,23 +33,11 @@ func (a *App) Execute(ctx context.Context, args []string, streams Streams) Outco
 		}
 		return current.present(current.renderHelp(parsed.Path), parsed.Path)
 	}
-	buildInput, err := command.record.payload.prepare(parsed.FlagValues, parsed.Operands, true)
+	run, err := command.record.payload.prepare(parsed.FlagValues, parsed.Operands, true)
 	if err != nil {
 		return current.present(Usage(err), parsed.Path)
 	}
-	input := buildInput()
-	if err := command.record.payload.checkInput(input); err != nil {
-		return current.present(classifyInputError(err), parsed.Path)
-	}
-	if len(parsed.Path) == 1 && parsed.Path[0] == "help" {
-		help, ok := input.(*helpInput)
-		if !ok {
-			return current.present(Failure(errors.New("built-in help input has an unexpected type")), parsed.Path)
-		}
-		return current.present(current.renderHelpTargets(help.Targets.Value), parsed.Path)
-	}
-	outcome := command.record.payload.run(Invocation{Context: ctx, Streams: streams}, input)
-	return current.present(outcome, parsed.Path)
+	return current.present(run(current), parsed.Path)
 }
 
 type execution struct {
@@ -61,6 +49,22 @@ type execution struct {
 	session  *internalcobra.Session
 }
 
+type commandExecution struct {
+	invocation            Invocation
+	renderHelpTargetsFunc func([]string) Outcome
+}
+
+func (current *execution) commandContext() commandExecution {
+	return commandExecution{
+		invocation:            Invocation{Context: current.ctx, Streams: current.streams},
+		renderHelpTargetsFunc: current.renderHelpTargets,
+	}
+}
+
+func (current commandExecution) renderHelpTargets(targets []string) Outcome {
+	return current.renderHelpTargetsFunc(targets)
+}
+
 func newExecution(app *App, ctx context.Context, streams Streams) *execution {
 	current := &execution{
 		app:     app,