treat \ as escape only before a separator

mapper_windows_test.go

@@ -0,0 +1,44 @@
+//go:build windows
+// +build windows
+
+package kong_test
+
+import (
+	"os"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestWindowsPathMapper(t *testing.T) {
+	var cli struct {
+		Path  string   `short:"p" type:"path"`
+		Files []string `short:"f" type:"path"`
+	}
+	wd, err := os.Getwd()
+	require.NoError(t, err, "Getwd failed")
+	p := mustNew(t, &cli)
+
+	_, err = p.Parse([]string{`-p`, `c:\an\absolute\path`, `-f`, `c:\second\absolute\path\`, `-f`, `relative\path\file`})
+	require.NoError(t, err)
+	require.Equal(t, `c:\an\absolute\path`, cli.Path)
+	require.Equal(t, []string{`c:\second\absolute\path\`, wd + `\relative\path\file`}, cli.Files)
+}
+
+func TestWindowsFileMapper(t *testing.T) {
+	type CLI struct {
+		File *os.File `arg:""`
+	}
+	var cli CLI
+	p := mustNew(t, &cli)
+	_, err := p.Parse([]string{"testdata\\file.txt"})
+	require.NoError(t, err)
+	require.NotNil(t, cli.File)
+	_ = cli.File.Close()
+	_, err = p.Parse([]string{"testdata\\missing.txt"})
+	require.Error(t, err)
+	require.Contains(t, err.Error(), "missing.txt: The system cannot find the file specified.")
+	_, err = p.Parse([]string{"-"})
+	require.NoError(t, err)
+	require.Equal(t, os.Stdin, cli.File)
+}