internal/helper: relocate from helper

This package is ugly and is pending removal only kept alive by xdg-dbus-proxy.

Its exported symbols are made available until v0.4.0 where it will be removed for #24.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/helper/args_test.go

@@ -0,0 +1,41 @@
+package helper_test
+
+import (
+	"errors"
+	"fmt"
+	"strings"
+	"syscall"
+	"testing"
+
+	"hakurei.app/internal/helper"
+)
+
+func TestArgsString(t *testing.T) {
+	t.Parallel()
+	wantString := strings.Join(wantArgs, " ")
+	if got := argsWt.(fmt.Stringer).String(); got != wantString {
+		t.Errorf("String: %q, want %q", got, wantString)
+	}
+}
+
+func TestNewCheckedArgs(t *testing.T) {
+	t.Parallel()
+
+	args := []string{"\x00"}
+	if _, err := helper.NewCheckedArgs(args...); !errors.Is(err, syscall.EINVAL) {
+		t.Errorf("NewCheckedArgs: error = %v, wantErr %v", err, syscall.EINVAL)
+	}
+
+	t.Run("must panic", func(t *testing.T) {
+		t.Parallel()
+
+		badPayload := []string{"\x00"}
+		defer func() {
+			wantPanic := "invalid argument"
+			if r := recover(); r != wantPanic {
+				t.Errorf("MustNewCheckedArgs: panic = %v, wantPanic %v", r, wantPanic)
+			}
+		}()
+		helper.MustNewCheckedArgs(badPayload...)
+	})
+}