jkawamoto/loci

//
// command/yaml.go
//
// Copyright (c) 2016-2017 Junpei Kawamoto
//
// This software is released under the MIT License.
//
// http://opensource.org/licenses/mit-license.php
//

package command

import "fmt"

// ListOrString defines an ambiguous type for YAML document, which can take
// a list of strings by default but also a single string literal.
type ListOrString []string

// UnmarshalYAML defines a way to unmarshal variables of ListOrString.
func (e *ListOrString) UnmarshalYAML(unmarshal func(interface{}) error) (err error) {

    var aux interface{}
    if err = unmarshal(&aux); err != nil {
        return
    }

    switch raw := aux.(type) {
    case string:
        *e = []string{raw}

    case []interface{}:
        list := make([]string, len(raw))
        for i, r := range raw {
            v, ok := r.(string)
            if !ok {
                return fmt.Errorf("An item in evn cannot be converted to a string: %v", aux)
            }
            list[i] = v
        }
        *e = list

    }
    return

}