From ba1498cd181bf47a2b154aca1bcade804b790b69 Mon Sep 17 00:00:00 2001
From: Ophestra <cat@gensokyo.uk>
Date: Sun, 23 Feb 2025 12:55:10 +0900
Subject: [PATCH] command: filter parse errors

Signed-off-by: Ophestra <cat@gensokyo.uk>
---
 command/command.go |  5 +++++
 command/parse.go   | 25 +++++++++++++++++++++++++
 2 files changed, 30 insertions(+)

diff --git a/command/command.go b/command/command.go
index eeec135..5533c4e 100644
--- a/command/command.go
+++ b/command/command.go
@@ -29,6 +29,11 @@ type (
 
 	Command interface {
 		Parse(arguments []string) error
+
+		// MustParse determines exit outcomes for Parse errors
+		// and calls handleError if [HandlerFunc] returns a non-nil error.
+		MustParse(arguments []string, handleError func(error))
+
 		baseNode[Command]
 	}
 	Node baseNode[Node]
diff --git a/command/parse.go b/command/parse.go
index 0212046..8e21433 100644
--- a/command/parse.go
+++ b/command/parse.go
@@ -3,6 +3,7 @@ package command
 import (
 	"errors"
 	"log"
+	"os"
 )
 
 var (
@@ -78,3 +79,27 @@ func (n *node) printf(format string, a ...any) {
 		n.logf(format, a...)
 	}
 }
+
+func (n *node) MustParse(arguments []string, handleError func(error)) {
+	switch err := n.Parse(arguments); err {
+	case nil:
+		return
+	case ErrHelp:
+		os.Exit(0)
+	case ErrNoMatch:
+		os.Exit(1)
+	case ErrEmptyTree:
+		os.Exit(1)
+	default:
+		var flagError FlagError
+		if !errors.As(err, &flagError) { // returned by HandlerFunc
+			handleError(err)
+			os.Exit(1)
+		}
+
+		if flagError.Success() {
+			os.Exit(0)
+		}
+		os.Exit(1)
+	}
+}