A sample code to show how to check if a directory is empty extending magicalbanana/env custom parser funcs

go

package config

import (
	"fmt"
	"io"
	"net/url"
	"os"
	"path/filepath"
	"reflect"
)

// URLType is a helper var that represents the `reflect.Type`` of `url.URL`
var URLType = reflect.TypeOf(url.URL{})

// ParseURL is a basic parser for the url.URL type that should be used with
// `env.ParseWithFuncs()`
func ParseURL(v string) (interface{}, error) {
	u, pErr := url.ParseRequestURI(v)
	if pErr != nil {
		return nil, pErr
	}
	return *u, nil
}

// MigrationsDir represents a file directory
type MigrationsDir string

// MigrationsDirType is a helper var that represents the `reflect.Type` of
// `Directory`
var MigrationsDirType = reflect.TypeOf(MigrationsDir(""))

// LoadMigrationsDir ...
func LoadMigrationsDir(v string) (interface{}, error) {
	fdir, err := os.Open(v)
	if err != nil {
		return nil, err
	}
	defer fdir.Close()

	finfo, err := fdir.Stat()
	if err != nil {
		return nil, err
	}

	if !finfo.Mode().IsDir() {
		return nil, fmt.Errorf("the given path: %s, is not a directory", fdir.Name())
	}

	ok, err := directoryEmpty(fdir)
	if err != nil {
		return nil, err
	}

	if ok {
		return nil, fmt.Errorf("the given path: %s, is empty", filepath.Dir(fdir.Name()))
	}
	return MigrationsDir(v), nil
}

func directoryEmpty(f *os.File) (bool, error) {
	_, err := f.Readdirnames(1)
	if err == io.EOF {
		return true, nil
	}
	return false, err
}