// The mapstructure package exposes functionality to convert an
// arbitrary map[string]interface{} into a native Go structure.
//
// The Go structure can be arbitrarily complex, containing slices,
// other structs, etc. and the decoder will properly decode nested
// maps and so on into the proper structures in the native Go struct.
// See the examples to see what the decoder is capable of.
package mapstructure
import (
"encoding/json"
"errors"
"fmt"
"reflect"
"sort"
"strconv"
"strings"
)
// DecodeHookFunc is the callback function that can be used for
// data transformations. See "DecodeHook" in the DecoderConfig
// struct.
//
// The type should be DecodeHookFuncType or DecodeHookFuncKind.
// Either is accepted. Types are a superset of Kinds (Types can return
// Kinds) and are generally a richer thing to use, but Kinds are simpler
// if you only need those.
//
// The reason DecodeHookFunc is multi-typed is for backwards compatibility:
// we started with Kinds and then realized Types were the better solution,
// but have a promise to not break backwards compat so we now support
// both.
type DecodeHookFunc interface{}
type DecodeHookFuncType func(reflect.Type, reflect.Type, interface{}) (interface{}, error)
type DecodeHookFuncKind func(reflect.Kind, reflect.Kind, interface{}) (interface{}, error)
// DecoderConfig is the configuration that is used to create a new decoder
// and allows customization of various aspects of decoding.
type DecoderConfig struct {
// DecodeHook, if set, will be called before any decoding and any
// type conversion (if WeaklyTypedInput is on). This lets you modify
// the values before they're set down onto the resulting struct.
//
// If an error is returned, the entire decode will fail with that
// error.
DecodeHook DecodeHookFunc
// If ErrorUnused is true, then it is an error for there to exist
// keys in the original map that were unused in the decoding process
// (extra keys).
ErrorUnused bool
// ZeroFields, if set to true, will zero fields before writing them.
// For example, a map will be emptied before decoded values are put in
// it. If this is false, a map will be merged.
ZeroFields bool
// If WeaklyTypedInput is true, the decoder will make the following
// "weak" conversions:
//
// - bools to string (true = "1", false = "0")
// - numbers to string (base 10)
// - bools to int/uint (true = 1, false = 0)
// - strings to int/uint (base implied by prefix)
// - int to bool (true if value != 0)
// - string to bool (accepts: 1, t, T, TRUE, true, True, 0, f, F,
// FALSE, false, False. Anything else is an error)
// - empty array = empty map and vice versa
// - negative numbers to overflowed uint values (base 10)
// - slice of maps to a merged map
// - single values are converted to slices if required. Each
// element is weakly decoded. For example: "4" can become []int{4}
// if the target type is an int slice.
//
WeaklyTypedInput bool
// Metadata is the struct that will contain extra metadata about
// the decoding. If this is nil, then no metadata will be tracked.
Metadata *Metadata
// Result is a pointer to the struct that will contain the decoded
// value.
Result interface{}
// The tag name that mapstructure reads for field names. This
// defaults to "mapstructure"
TagName string
}
// A Decoder takes a raw interface value and turns it into structured
// data, keeping track of rich error information along the way in case
// anything goes wrong. Unlike the basic top-level Decode method, you can
// more finely control how the Decoder behaves using the DecoderConfig
// structure. The top-level Decode method is just a convenience that sets
// up the most basic Decoder.
type Decoder struct {
config *DecoderConfig
}
// Metadata contains information about decoding a structure that
// is tedious or difficult to get otherwise.
type Metadata struct {
// Keys are the keys of the structure which were successfully decoded
Keys []string
// Unused is a slice of keys that were found in the raw value but
// weren't decoded since there was no matching field in the result interface
Unused []string
}
// Decode takes a map and uses reflection to convert it into the
// given Go native structure. val must be a pointer to a struct.
func Decode(m interface{}, rawVal interface{}) error {
config := &DecoderConfig{
Metadata: nil,
Result: rawVal,
}
decoder, err := NewDecoder(config)
if err != nil {
return err
}
return decoder.Decode(m)
}
// WeakDecode is the same as Decode but is shorthand to enable
// WeaklyTypedInput. See DecoderConfig for more info.
func WeakDecode(input, output interface{}) error {
config := &DecoderConfig{
Metadata: nil,
Result: output,
WeaklyTypedInput: true,
}
decoder, err := NewDecoder(config)
if err != nil {
return err
}
return decoder.Decode(input)
}
// NewDecoder returns a new decoder for the given configuration. Once
// a decoder has been returned, the same configuration must not be used
// again.
func NewDecoder(config *DecoderConfig) (*Decoder, error) {
val := reflect.ValueOf(config.Result)
if val.Kind() != reflect.Ptr {
return nil, errors.New("result must be a pointer")
}
val = val.Elem()
if !val.CanAddr() {
return nil, errors.New("result must be addressable (a pointer)")
}
if config.Metadata != nil {
if config.Metadata.Keys == nil {
config.Metadata.Keys = make([]string, 0)
}
if config.Metadata.Unused == nil {
config.Metadata.Unused = make([]string, 0)
}
}
if config.TagName == "" {
config.TagName = "mapstructure"
}
result := &Decoder{
config: config,
}
return result, nil
}
// Decode decodes the given raw interface to the target pointer specified
// by the configuration.
func (d *Decoder) Decode(raw interface{}) error {
return d.decode("", raw, reflect.ValueOf(d.config.Result).Elem())
}
// Decodes an unknown data type into a specific reflection value.
func (d *Decoder) decode(name string, data interface{}, val reflect.Value) error {
if data == nil {
// If the data is nil, then we don't set anything.
return nil
}
dataVal := reflect.ValueOf(data)
if !dataVal.IsValid() {
// If the data value is invalid, then we just set the value
// to be the zero value.
val.Set(reflect.Zero(val.Type()))
return nil
}
if d.config.DecodeHook != nil {
// We have a DecodeHook, so let's pre-process the data.
var err error
data, err = DecodeHookExec(
d.config.DecodeHook,
dataVal.Type(), val.Type(), data)
if err != nil {
return fmt.Errorf("error decoding '%s': %s", name, err)
}
}
var err error
dataKind := getKind(val)
switch dataKind {
case reflect.Bool:
err = d.decodeBool(name, data, val)
case reflect.Interface:
err = d.decodeBasic(name, data, val)
case reflect.String:
err = d.decodeString(name, data, val)
case reflect.Int:
err = d.decodeInt(name, data, val)
case reflect.Uint:
err = d.decodeUint(name, data, val)
case reflect.Float32:
err = d.decodeFloat(name, data, val)
case reflect.Struct:
err = d.decodeStruct(name, data, val)
case reflect.Map:
err = d.decodeMap(name, data, val)
case reflect.Ptr:
err = d.decodePtr(name, data, val)
case reflect.Slice:
err = d.decodeSlice(name, data, val)
case reflect.Func:
err = d.decodeFunc(name, data, val)
default:
// If we reached this point then we weren't able to decode it
return fmt.Errorf("%s: unsupported type: %s", name, dataKind)
}
// If we reached here, then we successfully decoded SOMETHING, so
// mark the key as used if we're tracking metadata.
if d.config.Metadata != nil && name != "" {
d.config.Metadata.Keys = append(d.config.Metadata.Keys, name)
}
return err
}
// This decodes a basic type (bool, int, string, etc.) and sets the
// value to "data" of that type.
func (d *Decoder) decodeBasic(name string, data interface{}, val reflect.Value) error {
dataVal := reflect.ValueOf(data)
if !dataVal.IsValid() {
dataVal = reflect.Zero(val.Type())
}
dataValType := dataVal.Type()
if !dataValType.AssignableTo(val.Type()) {
return fmt.Errorf(
"'%s' expected type '%s', got '%s'",
name, val.Type(), dataValType)
}
val.Set(dataVal)
return nil
}
func (d *Decoder) decodeString(name string, data interface{}, val reflect.Value) error {
dataVal := reflect.ValueOf(data)
dataKind := getKind(dataVal)
converted := true
switch {
case dataKind == reflect.String:
val.SetString(dataVal.String())
case dataKind == reflect.Bool && d.config.WeaklyTypedInput:
if dataVal.Bool() {
val.SetString("1")
} else {
val.SetString("0")
}
case dataKind == reflect.Int && d.config.WeaklyTypedInput:
val.SetString(strconv.FormatInt(dataVal.Int(), 10))
case dataKind == reflect.Uint && d.config.WeaklyTypedInput:
val.SetString(strconv.FormatUint(dataVal.Uint(), 10))
case dataKind == reflect.Float32 && d.config.WeaklyTypedInput:
val.SetString(strconv.FormatFloat(dataVal.Float(), 'f', -1, 64))
case dataKind == reflect.Slice && d.config.WeaklyTypedInput:
dataType := dataVal.Type()
elemKind := dataType.Elem().Kind()
switch {
case elemKind == reflect.Uint8:
val.SetString(string(dataVal.Interface().([]uint8)))
default:
converted = false
}
default:
converted = false
}
if !converted {
return fmt.Errorf(
"'%s' expected type '%s', got unconvertible type '%s'",
name, val.Type(), dataVal.Type())
}
return nil
}
func (d *Decoder) decodeInt(name string, data interface{}, val reflect.Value) error {
dataVal := reflect.ValueOf(data)
dataKind := getKind(dataVal)
dataType := dataVal.Type()
switch {
case dataKind == reflect.Int:
val.SetInt(dataVal.Int())
case dataKind == reflect.Uint:
val.SetInt(int64(dataVal.Uint()))
case dataKind == reflect.Float32:
val.SetInt(int64(dataVal.Float()))
case dataKind == reflect.Bool && d.config.WeaklyTypedInput:
if dataVal.Bool() {
val.SetInt(1)
} else {
val.SetInt(0)
}
case dataKind == reflect.String && d.config.WeaklyTypedInput:
i, err := strconv.ParseInt(dataVal.String(), 0, val.Type().Bits())
if err == nil {
val.SetInt(i)
} else {
return fmt.Errorf("cannot parse '%s' as int: %s", name, err)
}
case dataType.PkgPath() == "encoding/json" && dataType.Name() == "Number":
jn := data.(json.Number)
i, err := jn.Int64()
if err != nil {
return fmt.Errorf(
"error decoding json.Number into %s: %s", name, err)
}
val.SetInt(i)
default:
return fmt.Errorf(
"'%s' expected type '%s', got unconvertible type '%s'",
name, val.Type(), dataVal.Type())
}
return nil
}
func (d *Decoder) decodeUint(name string, data interface{}, val reflect.Value) error {
dataVal := reflect.ValueOf(data)
dataKind := getKind(dataVal)
switch {
case dataKind == reflect.Int:
i := dataVal.Int()
if i < 0 && !d.config.WeaklyTypedInput {
return fmt.Errorf("cannot parse '%s', %d overflows uint",
name, i)
}
val.SetUint(uint64(i))
case dataKind == reflect.Uint:
val.SetUint(dataVal.Uint())
case dataKind == reflect.Float32:
f := dataVal.Float()
if f < 0 && !d.config.WeaklyTypedInput {
return fmt.Errorf("cannot parse '%s', %f overflows uint",
name, f)
}
val.SetUint(uint64(f))
case dataKind == reflect.Bool && d.config.WeaklyTypedInput:
if dataVal.Bool() {
val.SetUint(1)
} else {
val.SetUint(0)
}
case dataKind == reflect.String && d.config.WeaklyTypedInput:
i, err := strconv.ParseUint(dataVal.String(), 0, val.Type().Bits())
if err == nil {
val.SetUint(i)
} else {
return fmt.Errorf("cannot parse '%s' as uint: %s", name, err)
}
default:
return fmt.Errorf(
"'%s' expected type '%s', got unconvertible type '%s'",
name, val.Type(), dataVal.Type())
}
return nil
}
func (d *Decoder) decodeBool(name string, data interface{}, val reflect.Value) error {
dataVal := reflect.ValueOf(data)
dataKind := getKind(dataVal)
switch {
case dataKind == reflect.Bool:
val.SetBool(dataVal.Bool())
case dataKind == reflect.Int && d.config.WeaklyTypedInput:
val.SetBool(dataVal.Int() != 0)
case dataKind == reflect.Uint && d.config.WeaklyTypedInput:
val.SetBool(dataVal.Uint() != 0)
case dataKind == reflect.Float32 && d.config.WeaklyTypedInput:
val.SetBool(dataVal.Float() != 0)
case dataKind == reflect.String && d.config.WeaklyTypedInput:
b, err := strconv.ParseBool(dataVal.String())
if err == nil {
val.SetBool(b)
} else if dataVal.String() == "" {
val.SetBool(false)
} else {
return fmt.Errorf("cannot parse '%s' as bool: %s", name, err)
}
default:
return fmt.Errorf(
"'%s' expected type '%s', got unconvertible type '%s'",
name, val.Type(), dataVal.Type())
}
return nil
}
func (d *Decoder) decodeFloat(name string, data interface{}, val reflect.Value) error {
dataVal := reflect.ValueOf(data)
dataKind := getKind(dataVal)
dataType := dataVal.Type()
switch {
case dataKind == reflect.Int:
val.SetFloat(float64(dataVal.Int()))
case dataKind == reflect.Uint:
val.SetFloat(float64(dataVal.Uint()))
case dataKind == reflect.Float32:
val.SetFloat(float64(dataVal.Float()))
case dataKind == reflect.Bool && d.config.WeaklyTypedInput:
if dataVal.Bool() {
val.SetFloat(1)
} else {
val.SetFloat(0)
}
case dataKind == reflect.String && d.config.WeaklyTypedInput:
f, err := strconv.ParseFloat(dataVal.String(), val.Type().Bits())
if err == nil {
val.SetFloat(f)
} else {
return fmt.Errorf("cannot parse '%s' as float: %s", name, err)
}
case dataType.PkgPath() == "encoding/json" && dataType.Name() == "Number":
jn := data.(json.Number)
i, err := jn.Float64()
if err != nil {
return fmt.Errorf(
"error decoding json.Number into %s: %s", name, err)
}
val.SetFloat(i)
default:
return fmt.Errorf(
"'%s' expected type '%s', got unconvertible type '%s'",
name, val.Type(), dataVal.Type())
}
return nil
}
func (d *Decoder) decodeMap(name string, data interface{}, val reflect.Value) error {
valType := val.Type()
valKeyType := valType.Key()
valElemType := valType.Elem()
// By default we overwrite keys in the current map
valMap := val
// If the map is nil or we're purposely zeroing fields, make a new map
if valMap.IsNil() || d.config.ZeroFields {
// Make a new map to hold our result
mapType := reflect.MapOf(valKeyType, valElemType)
valMap = reflect.MakeMap(mapType)
}
// Check input type
dataVal := reflect.Indirect(reflect.ValueOf(data))
if dataVal.Kind() != reflect.Map {
// In weak mode, we accept a slice of maps as an input...
if d.config.WeaklyTypedInput {
switch dataVal.Kind() {
case reflect.Array, reflect.Slice:
// Special case for BC reasons (covered by tests)
if dataVal.Len() == 0 {
val.Set(valMap)
return nil
}
for i := 0; i < dataVal.Len(); i++ {
err := d.decode(
fmt.Sprintf("%s[%d]", name, i),
dataVal.Index(i).Interface(), val)
if err != nil {
return err
}
}
return nil
}
}
return fmt.Errorf("'%s' expected a map, got '%s'", name, dataVal.Kind())
}
// Accumulate errors
errors := make([]string, 0)
for _, k := range dataVal.MapKeys() {
fieldName := fmt.Sprintf("%s[%s]", name, k)
// First decode the key into the proper type
currentKey := reflect.Indirect(reflect.New(valKeyType))
if err := d.decode(fieldName, k.Interface(), currentKey); err != nil {
errors = appendErrors(errors, err)
continue
}
// Next decode the data into the proper type
v := dataVal.MapIndex(k).Interface()
currentVal := reflect.Indirect(reflect.New(valElemType))
if err := d.decode(fieldName, v, currentVal); err != nil {
errors = appendErrors(errors, err)
continue
}
valMap.SetMapIndex(currentKey, currentVal)
}
// Set the built up map to the value
val.Set(valMap)
// If we had errors, return those
if len(errors) > 0 {
return &Error{errors}
}
return nil
}
func (d *Decoder) decodePtr(name string, data interface{}, val reflect.Value) error {
// Create an element of the concrete (non pointer) type and decode
// into that. Then set the value of the pointer to this type.
valType := val.Type()
valElemType := valType.Elem()
realVal := val
if realVal.IsNil() || d.config.ZeroFields {
realVal = reflect.New(valElemType)
}
if err := d.decode(name, data, reflect.Indirect(realVal)); err != nil {
return err
}
val.Set(realVal)
return nil
}
func (d *Decoder) decodeFunc(name string, data interface{}, val reflect.Value) error {
// Create an element of the concrete (non pointer) type and decode
// into that. Then set the value of the pointer to this type.
dataVal := reflect.Indirect(reflect.ValueOf(data))
if val.Type() != dataVal.Type() {
return fmt.Errorf(
"'%s' expected type '%s', got unconvertible type '%s'",
name, val.Type(), dataVal.Type())
}
val.Set(dataVal)
return nil
}
func (d *Decoder) decodeSlice(name string, data interface{}, val reflect.Value) error {
dataVal := reflect.Indirect(reflect.ValueOf(data))
dataValKind := dataVal.Kind()
valType := val.Type()
valElemType := valType.Elem()
sliceType := reflect.SliceOf(valElemType)
valSlice := val
if valSlice.IsNil() || d.config.ZeroFields {
// Check input type
if dataValKind != reflect.Array && dataValKind != reflect.Slice {
if d.config.WeaklyTypedInput {
switch {
// Empty maps turn into empty slices
case dataValKind == reflect.Map:
if dataVal.Len() == 0 {
val.Set(reflect.MakeSlice(sliceType, 0, 0))
return nil
}
// All other types we try to convert to the slice type
// and "lift" it into it. i.e. a string becomes a string slice.
default:
// Just re-try this function with data as a slice.
return d.decodeSlice(name, []interface{}{data}, val)
}
}
return fmt.Errorf(
"'%s': source data must be an array or slice, got %s", name, dataValKind)
}
// Make a new slice to hold our result, same size as the original data.
valSlice = reflect.MakeSlice(sliceType, dataVal.Len(), dataVal.Len())
}
// Accumulate any errors
errors := make([]string, 0)
for i := 0; i < dataVal.Len(); i++ {
currentData := dataVal.Index(i).Interface()
for valSlice.Len() <= i {
valSlice = reflect.Append(valSlice, reflect.Zero(valElemType))
}
currentField := valSlice.Index(i)
fieldName := fmt.Sprintf("%s[%d]", name, i)
if err := d.decode(fieldName, currentData, currentField); err != nil {
errors = appendErrors(errors, err)
}
}
// Finally, set the value to the slice we built up
val.Set(valSlice)
// If there were errors, we return those
if len(errors) > 0 {
return &Error{errors}
}
return nil
}
func (d *Decoder) decodeStruct(name string, data interface{}, val reflect.Value) error {
dataVal := reflect.Indirect(reflect.ValueOf(data))
// If the type of the value to write to and the data match directly,
// then we just set it directly instead of recursing into the structure.
if dataVal.Type() == val.Type() {
val.Set(dataVal)
return nil
}
dataValKind := dataVal.Kind()
if dataValKind != reflect.Map {
return fmt.Errorf("'%s' expected a map, got '%s'", name, dataValKind)
}
dataValType := dataVal.Type()
if kind := dataValType.Key().Kind(); kind != reflect.String && kind != reflect.Interface {
return fmt.Errorf(
"'%s' needs a map with string keys, has '%s' keys",
name, dataValType.Key().Kind())
}
dataValKeys := make(map[reflect.Value]struct{})
dataValKeysUnused := make(map[interface{}]struct{})
for _, dataValKey := range dataVal.MapKeys() {
dataValKeys[dataValKey] = struct{}{}
dataValKeysUnused[dataValKey.Interface()] = struct{}{}
}
errors := make([]string, 0)
// This slice will keep track of all the structs we'll be decoding.
// There can be more than one struct if there are embedded structs
// that are squashed.
structs := make([]reflect.Value, 1, 5)
structs[0] = val
// Compile the list of all the fields that we're going to be decoding
// from all the structs.
fields := make(map[*reflect.StructField]reflect.Value)
for len(structs) > 0 {
structVal := structs[0]
structs = structs[1:]
structType := structVal.Type()
for i := 0; i < structType.NumField(); i++ {
fieldType := structType.Field(i)
fieldKind := fieldType.Type.Kind()
// If "squash" is specified in the tag, we squash the field down.
squash := false
tagParts := strings.Split(fieldType.Tag.Get(d.config.TagName), ",")
for _, tag := range tagParts[1:] {
if tag == "squash" {
squash = true
break
}
}
if squash {
if fieldKind != reflect.Struct {
errors = appendErrors(errors,
fmt.Errorf("%s: unsupported type for squash: %s", fieldType.Name, fieldKind))
} else {
structs = append(structs, val.FieldByName(fieldType.Name))
}
continue
}
// Normal struct field, store it away
fields[&fieldType] = structVal.Field(i)
}
}
for fieldType, field := range fields {
fieldName := fieldType.Name
tagValue := fieldType.Tag.Get(d.config.TagName)
tagValue = strings.SplitN(tagValue, ",", 2)[0]
if tagValue != "" {
fieldName = tagValue
}
rawMapKey := reflect.ValueOf(fieldName)
rawMapVal := dataVal.MapIndex(rawMapKey)
if !rawMapVal.IsValid() {
// Do a slower search by iterating over each key and
// doing case-insensitive search.
for dataValKey := range dataValKeys {
mK, ok := dataValKey.Interface().(string)
if !ok {
// Not a string key
continue
}
if strings.EqualFold(mK, fieldName) {
rawMapKey = dataValKey
rawMapVal = dataVal.MapIndex(dataValKey)
break
}
}
if !rawMapVal.IsValid() {
// There was no matching key in the map for the value in
// the struct. Just ignore.
continue
}
}
// Delete the key we're using from the unused map so we stop tracking
delete(dataValKeysUnused, rawMapKey.Interface())
if !field.IsValid() {
// This should never happen
panic("field is not valid")
}
// If we can't set the field, then it is unexported or something,
// and we just continue onwards.
if !field.CanSet() {
continue
}
// If the name is empty string, then we're at the root, and we
// don't dot-join the fields.
if name != "" {
fieldName = fmt.Sprintf("%s.%s", name, fieldName)
}
if err := d.decode(fieldName, rawMapVal.Interface(), field); err != nil {
errors = appendErrors(errors, err)
}
}
if d.config.ErrorUnused && len(dataValKeysUnused) > 0 {
keys := make([]string, 0, len(dataValKeysUnused))
for rawKey := range dataValKeysUnused {
keys = append(keys, rawKey.(string))
}
sort.Strings(keys)
err := fmt.Errorf("'%s' has invalid keys: %s", name, strings.Join(keys, ", "))
errors = appendErrors(errors, err)
}
if len(errors) > 0 {
return &Error{errors}
}
// Add the unused keys to the list of unused keys if we're tracking metadata
if d.config.Metadata != nil {
for rawKey := range dataValKeysUnused {
key := rawKey.(string)
if name != "" {
key = fmt.Sprintf("%s.%s", name, key)
}
d.config.Metadata.Unused = append(d.config.Metadata.Unused, key)
}
}
return nil
}
func getKind(val reflect.Value) reflect.Kind {
kind := val.Kind()
switch {
case kind >= reflect.Int && kind <= reflect.Int64:
return reflect.Int
case kind >= reflect.Uint && kind <= reflect.Uint64:
return reflect.Uint
case kind >= reflect.Float32 && kind <= reflect.Float64:
return reflect.Float32
default:
return kind
}
}
