feat(super-flags): Add GetPath method in superflags (#258)

Add GetPath() method on super flags. It is required because paths
needs to handled differently than normal string arguments. For example,
a path `~/abc` needs to be resolved to `/home/user/abc`.

z/flags.go

@@ -3,6 +3,9 @@ package z
 import (
 	"fmt"
 	"log"
+	"os"
+	"os/user"
+	"path/filepath"
 	"sort"
 	"strconv"
 	"strings"
@@ -275,3 +278,34 @@ func (sf *SuperFlag) GetString(opt string) string {
 	}
 	return sf.m[opt]
 }
+
+func (sf *SuperFlag) GetPath(opt string) string {
+	p := sf.GetString(opt)
+	path, err := expandPath(p)
+	if err != nil {
+		log.Fatalf("Failed to get path: %+v", err)
+	}
+	return path
+}
+
+// expandPath expands the paths containing ~ to /home/user. It also computes the absolute path
+// from the relative paths. For example: ~/abc/../cef will be transformed to /home/user/cef.
+func expandPath(path string) (string, error) {
+	if len(path) == 0 {
+		return "", nil
+	}
+	if path[0] == '~' && (len(path) == 1 || os.IsPathSeparator(path[1])) {
+		usr, err := user.Current()
+		if err != nil {
+			return "", errors.Wrap(err, "Failed to get the home directory of the user")
+		}
+		path = filepath.Join(usr.HomeDir, path[1:])
+	}
+
+	var err error
+	path, err = filepath.Abs(path)
+	if err != nil {
+		return "", errors.Wrap(err, "Failed to generate absolute path")
+	}
+	return path, nil
+}

z/flags_test.go

@@ -1,6 +1,10 @@
 package z
 
 import (
+	"fmt"
+	"os"
+	"os/user"
+	"path/filepath"
 	"testing"
 	"time"
 
@@ -37,3 +41,49 @@ func TestFlagDefault(t *testing.T) {
 	require.Equal(t, true, f.GetBool("one"))
 	require.Equal(t, int64(4), f.GetInt64("two"))
 }
+
+func TestGetPath(t *testing.T) {
+
+	usr, err := user.Current()
+	require.NoError(t, err)
+	homeDir := usr.HomeDir
+	cwd, err := os.Getwd()
+	require.NoError(t, err)
+
+	tests := []struct {
+		path     string
+		expected string
+	}{
+		{
+			"/home/user/file.txt",
+			"/home/user/file.txt",
+		},
+		{
+			"~/file.txt",
+			filepath.Join(homeDir, "file.txt"),
+		},
+		{
+			"~/abc/../file.txt",
+			filepath.Join(homeDir, "file.txt"),
+		},
+		{
+			"~/",
+			homeDir,
+		},
+		{
+			"~filename",
+			filepath.Join(cwd, "~filename"),
+		},
+	}
+
+	get := func(p string) string {
+		opt := fmt.Sprintf("file=%s", p)
+		sf := NewSuperFlag(opt)
+		return sf.GetPath("file")
+	}
+
+	for _, tc := range tests {
+		actual := get(tc.path)
+		require.Equalf(t, tc.expected, actual, "Failed on testcase: %s", tc.path)
+	}
+}