package toml
import (
"bytes"
"encoding"
"encoding/json"
"fmt"
"io"
"io/fs"
"math"
"os"
"reflect"
"strconv"
"strings"
"time"
)
// Unmarshaler is the interface implemented by objects that can unmarshal a
// TOML description of themselves.
type Unmarshaler interface {
UnmarshalTOML(any) error
}
// Unmarshal decodes the contents of data in TOML format into a pointer v.
//
// See [Decoder] for a description of the decoding process.
func Unmarshal(data []byte, v any) error {
_, err := NewDecoder(bytes.NewReader(data)).Decode(v)
return err
}
// Decode the TOML data in to the pointer v.
//
// See [Decoder] for a description of the decoding process.
func Decode(data string, v any) (MetaData, error) {
return NewDecoder(strings.NewReader(data)).Decode(v)
}
// DecodeFile reads the contents of a file and decodes it with [Decode].
func DecodeFile(path string, v any) (MetaData, error) {
fp, err := os.Open(path)
if err != nil {
return MetaData{}, err
}
defer fp.Close()
return NewDecoder(fp).Decode(v)
}
// DecodeFS reads the contents of a file from [fs.FS] and decodes it with
// [Decode].
func DecodeFS(fsys fs.FS, path string, v any) (MetaData, error) {
fp, err := fsys.Open(path)
if err != nil {
return MetaData{}, err
}
defer fp.Close()
return NewDecoder(fp).Decode(v)
}
// Primitive is a TOML value that hasn't been decoded into a Go value.
//
// This type can be used for any value, which will cause decoding to be delayed.
// You can use [PrimitiveDecode] to "manually" decode these values.
//
// NOTE: The underlying representation of a `Primitive` value is subject to
// change. Do not rely on it.
//
// NOTE: Primitive values are still parsed, so using them will only avoid the
// overhead of reflection. They can be useful when you don't know the exact type
// of TOML data until runtime.
type Primitive struct {
undecoded any
context Key
}
// The significand precision for float32 and float64 is 24 and 53 bits; this is
// the range a natural number can be stored in a float without loss of data.
const (
maxSafeFloat32Int = 16777215 // 2^24-1
maxSafeFloat64Int = int64(9007199254740991) // 2^53-1
)
// Decoder decodes TOML data.
//
// TOML tables correspond to Go structs or maps; they can be used
// interchangeably, but structs offer better type safety.
//
// TOML table arrays correspond to either a slice of structs or a slice of maps.
//
// TOML datetimes correspond to [time.Time]. Local datetimes are parsed in the
// local timezone.
//
// [time.Duration] types are treated as nanoseconds if the TOML value is an
// integer, or they're parsed with time.ParseDuration() if they're strings.
//
// All other TOML types (float, string, int, bool and array) correspond to the
// obvious Go types.
//
// An exception to the above rules is if a type implements the TextUnmarshaler
// interface, in which case any primitive TOML value (floats, strings, integers,
// booleans, datetimes) will be converted to a []byte and given to the value's
// UnmarshalText method. See the Unmarshaler example for a demonstration with
// email addresses.
//
// # Key mapping
//
// TOML keys can map to either keys in a Go map or field names in a Go struct.
// The special `toml` struct tag can be used to map TOML keys to struct fields
// that don't match the key name exactly (see the example). A case insensitive
// match to struct names will be tried if an exact match can't be found.
//
// The mapping between TOML values and Go values is loose. That is, there may
// exist TOML values that cannot be placed into your representation, and there
// may be parts of your representation that do not correspond to TOML values.
// This loose mapping can be made stricter by using the IsDefined and/or
// Undecoded methods on the MetaData returned.
//
// This decoder does not handle cyclic types. Decode will not terminate if a
// cyclic type is passed.
type Decoder struct {
r io.Reader
}
// NewDecoder creates a new Decoder.
func NewDecoder(r io.Reader) *Decoder {
return &Decoder{r: r}
}
var (
unmarshalToml = reflect.TypeOf((*Unmarshaler)(nil)).Elem()
unmarshalText = reflect.TypeOf((*encoding.TextUnmarshaler)(nil)).Elem()
primitiveType = reflect.TypeOf((*Primitive)(nil)).Elem()
)
// Decode TOML data in to the pointer `v`.
func (dec *Decoder) Decode(v any) (MetaData, error) {
rv := reflect.ValueOf(v)
if rv.Kind() != reflect.Ptr {
s := "%q"
if reflect.TypeOf(v) == nil {
s = "%v"
}
return MetaData{}, fmt.Errorf("toml: cannot decode to non-pointer "+s, reflect.TypeOf(v))
}
if rv.IsNil() {
return MetaData{}, fmt.Errorf("toml: cannot decode to nil value of %q", reflect.TypeOf(v))
}
// Check if this is a supported type: struct, map, any, or something that
// implements UnmarshalTOML or UnmarshalText.
rv = indirect(rv)
rt := rv.Type()
if rv.Kind() != reflect.Struct && rv.Kind() != reflect.Map &&
!(rv.Kind() == reflect.Interface && rv.NumMethod() == 0) &&
!rt.Implements(unmarshalToml) && !rt.Implements(unmarshalText) {
return MetaData{}, fmt.Errorf("toml: cannot decode to type %s", rt)
}
// TODO: parser should read from io.Reader? Or at the very least, make it
// read from []byte rather than string
data, err := io.ReadAll(dec.r)
if err != nil {
return MetaData{}, err
}
p, err := parse(string(data))
if err != nil {
return MetaData{}, err
}
md := MetaData{
mapping: p.mapping,
keyInfo: p.keyInfo,
keys: p.ordered,
decoded: make(map[string]struct{}, len(p.ordered)),
context: nil,
data: data,
}
return md, md.unify(p.mapping, rv)
}
// PrimitiveDecode is just like the other Decode* functions, except it decodes a
// TOML value that has already been parsed. Valid primitive values can *only* be
// obtained from values filled by the decoder functions, including this method.
// (i.e., v may contain more [Primitive] values.)
//
// Meta data for primitive values is included in the meta data returned by the
// Decode* functions with one exception: keys returned by the Undecoded method
// will only reflect keys that were decoded. Namely, any keys hidden behind a
// Primitive will be considered undecoded. Executing this method will update the
// undecoded keys in the meta data. (See the example.)
func (md *MetaData) PrimitiveDecode(primValue Primitive, v any) error {
md.context = primValue.context
defer func() { md.context = nil }()
return md.unify(primValue.undecoded, rvalue(v))
}
// unify performs a sort of type unification based on the structure of `rv`,
// which is the client representation.
//
// Any type mismatch produces an error. Finding a type that we don't know
// how to handle produces an unsupported type error.
func (md *MetaData) unify(data any, rv reflect.Value) error {
// Special case. Look for a `Primitive` value.
// TODO: #76 would make this superfluous after implemented.
if rv.Type() == primitiveType {
// Save the undecoded data and the key context into the primitive
// value.
context := make(Key, len(md.context))
copy(context, md.context)
rv.Set(reflect.ValueOf(Primitive{
undecoded: data,
context: context,
}))
return nil
}
rvi := rv.Interface()
if v, ok := rvi.(Unmarshaler); ok {
err := v.UnmarshalTOML(data)
if err != nil {
return md.parseErr(err)
}
return nil
}
if v, ok := rvi.(encoding.TextUnmarshaler); ok {
return md.unifyText(data, v)
}
// TODO:
// The behavior here is incorrect whenever a Go type satisfies the
// encoding.TextUnmarshaler interface but also corresponds to a TOML hash or
// array. In particular, the unmarshaler should only be applied to primitive
// TOML values. But at this point, it will be applied to all kinds of values
// and produce an incorrect error whenever those values are hashes or arrays
// (including arrays of tables).
k := rv.Kind()
if k >= reflect.Int && k <= reflect.Uint64 {
return md.unifyInt(data, rv)
}
switch k {
case reflect.Struct:
return md.unifyStruct(data, rv)
case reflect.Map:
return md.unifyMap(data, rv)
case reflect.Array:
return md.unifyArray(data, rv)
case reflect.Slice:
return md.unifySlice(data, rv)
case reflect.String:
return md.unifyString(data, rv)
case reflect.Bool:
return md.unifyBool(data, rv)
case reflect.Interface:
if rv.NumMethod() > 0 { /// Only empty interfaces are supported.
return md.e("unsupported type %s", rv.Type())
}
return md.unifyAnything(data, rv)
case reflect.Float32, reflect.Float64:
return md.unifyFloat64(data, rv)
}
return md.e("unsupported type %s", rv.Kind())
}
func (md *MetaData) unifyStruct(mapping any, rv reflect.Value) error {
tmap, ok := mapping.(map[string]any)
if !ok {
if mapping == nil {
return nil
}
return md.e("type mismatch for %s: expected table but found %s", rv.Type().String(), fmtType(mapping))
}
for key, datum := range tmap {
var f *field
fields := cachedTypeFields(rv.Type())
for i := range fields {
ff := &fields[i]
if ff.name == key {
f = ff
break
}
if f == nil && strings.EqualFold(ff.name, key) {
f = ff
}
}
if f != nil {
subv := rv
for _, i := range f.index {
subv = indirect(subv.Field(i))
}
if isUnifiable(subv) {
md.decoded[md.context.add(key).String()] = struct{}{}
md.context = append(md.context, key)
err := md.unify(datum, subv)
if err != nil {
return err
}
md.context = md.context[0 : len(md.context)-1]
} else if f.name != "" {
return md.e("cannot write unexported field %s.%s", rv.Type().String(), f.name)
}
}
}
return nil
}
func (md *MetaData) unifyMap(mapping any, rv reflect.Value) error {
keyType := rv.Type().Key().Kind()
if keyType != reflect.String && keyType != reflect.Interface {
return fmt.Errorf("toml: cannot decode to a map with non-string key type (%s in %q)",
keyType, rv.Type())
}
tmap, ok := mapping.(map[string]any)
if !ok {
if tmap == nil {
return nil
}
return md.badtype("map", mapping)
}
if rv.IsNil() {
rv.Set(reflect.MakeMap(rv.Type()))
}
for k, v := range tmap {
md.decoded[md.context.add(k).String()] = struct{}{}
md.context = append(md.context, k)
rvval := reflect.Indirect(reflect.New(rv.Type().Elem()))
err := md.unify(v, indirect(rvval))
if err != nil {
return err
}
md.context = md.context[0 : len(md.context)-1]
rvkey := indirect(reflect.New(rv.Type().Key()))
switch keyType {
case reflect.Interface:
rvkey.Set(reflect.ValueOf(k))
case reflect.String:
rvkey.SetString(k)
}
rv.SetMapIndex(rvkey, rvval)
}
return nil
}
func (md *MetaData) unifyArray(data any, rv reflect.Value) error {
datav := reflect.ValueOf(data)
if datav.Kind() != reflect.Slice {
if !datav.IsValid() {
return nil
}
return md.badtype("slice", data)
}
if l := datav.Len(); l != rv.Len() {
return md.e("expected array length %d; got TOML array of length %d", rv.Len(), l)
}
return md.unifySliceArray(datav, rv)
}
func (md *MetaData) unifySlice(data any, rv reflect.Value) error {
datav := reflect.ValueOf(data)
if datav.Kind() != reflect.Slice {
if !datav.IsValid() {
return nil
}
return md.badtype("slice", data)
}
n := datav.Len()
if rv.IsNil() || rv.Cap() < n {
rv.Set(reflect.MakeSlice(rv.Type(), n, n))
}
rv.SetLen(n)
return md.unifySliceArray(datav, rv)
}
func (md *MetaData) unifySliceArray(data, rv reflect.Value) error {
l := data.Len()
for i := 0; i < l; i++ {
err := md.unify(data.Index(i).Interface(), indirect(rv.Index(i)))
if err != nil {
return err
}
}
return nil
}
func (md *MetaData) unifyString(data any, rv reflect.Value) error {
_, ok := rv.Interface().(json.Number)
if ok {
if i, ok := data.(int64); ok {
rv.SetString(strconv.FormatInt(i, 10))
} else if f, ok := data.(float64); ok {
rv.SetString(strconv.FormatFloat(f, 'f', -1, 64))
} else {
return md.badtype("string", data)
}
return nil
}
if s, ok := data.(string); ok {
rv.SetString(s)
return nil
}
return md.badtype("string", data)
}
func (md *MetaData) unifyFloat64(data any, rv reflect.Value) error {
rvk := rv.Kind()
if num, ok := data.(float64); ok {
switch rvk {
case reflect.Float32:
if num < -math.MaxFloat32 || num > math.MaxFloat32 {
return md.parseErr(errParseRange{i: num, size: rvk.String()})
}
fallthrough
case reflect.Float64:
rv.SetFloat(num)
default:
panic("bug")
}
return nil
}
if num, ok := data.(int64); ok {
if (rvk == reflect.Float32 && (num < -maxSafeFloat32Int || num > maxSafeFloat32Int)) ||
(rvk == reflect.Float64 && (num < -maxSafeFloat64Int || num > maxSafeFloat64Int)) {
return md.parseErr(errUnsafeFloat{i: num, size: rvk.String()})
}
rv.SetFloat(float64(num))
return nil
}
return md.badtype("float", data)
}
func (md *MetaData) unifyInt(data any, rv reflect.Value) error {
_, ok := rv.Interface().(time.Duration)
if ok {
// Parse as string duration, and fall back to regular integer parsing
// (as nanosecond) if this is not a string.
if s, ok := data.(string); ok {
dur, err := time.ParseDuration(s)
if err != nil {
return md.parseErr(errParseDuration{s})
}
rv.SetInt(int64(dur))
return nil
}
}
num, ok := data.(int64)
if !ok {
return md.badtype("integer", data)
}
rvk := rv.Kind()
switch {
case rvk >= reflect.Int && rvk <= reflect.Int64:
if (rvk == reflect.Int8 && (num < math.MinInt8 || num > math.MaxInt8)) ||
(rvk == reflect.Int16 && (num < math.MinInt16 || num > math.MaxInt16)) ||
(rvk == reflect.Int32 && (num < math.MinInt32 || num > math.MaxInt32)) {
return md.parseErr(errParseRange{i: num, size: rvk.String()})
}
rv.SetInt(num)
case rvk >= reflect.Uint && rvk <= reflect.Uint64:
unum := uint64(num)
if rvk == reflect.Uint8 && (num < 0 || unum > math.MaxUint8) ||
rvk == reflect.Uint16 && (num < 0 || unum > math.MaxUint16) ||
rvk == reflect.Uint32 && (num < 0 || unum > math.MaxUint32) {
return md.parseErr(errParseRange{i: num, size: rvk.String()})
}
rv.SetUint(unum)
default:
panic("unreachable")
}
return nil
}
func (md *MetaData) unifyBool(data any, rv reflect.Value) error {
if b, ok := data.(bool); ok {
rv.SetBool(b)
return nil
}
return md.badtype("boolean", data)
}
func (md *MetaData) unifyAnything(data any, rv reflect.Value) error {
rv.Set(reflect.ValueOf(data))
return nil
}
func (md *MetaData) unifyText(data any, v encoding.TextUnmarshaler) error {
var s string
switch sdata := data.(type) {
case Marshaler:
text, err := sdata.MarshalTOML()
if err != nil {
return err
}
s = string(text)
case encoding.TextMarshaler:
text, err := sdata.MarshalText()
if err != nil {
return err
}
s = string(text)
case fmt.Stringer:
s = sdata.String()
case string:
s = sdata
case bool:
s = fmt.Sprintf("%v", sdata)
case int64:
s = fmt.Sprintf("%d", sdata)
case float64:
s = fmt.Sprintf("%f", sdata)
default:
return md.badtype("primitive (string-like)", data)
}
if err := v.UnmarshalText([]byte(s)); err != nil {
return md.parseErr(err)
}
return nil
}
func (md *MetaData) badtype(dst string, data any) error {
return md.e("incompatible types: TOML value has type %s; destination has type %s", fmtType(data), dst)
}
func (md *MetaData) parseErr(err error) error {
k := md.context.String()
return ParseError{
LastKey: k,
Position: md.keyInfo[k].pos,
Line: md.keyInfo[k].pos.Line,
err: err,
input: string(md.data),
}
}
func (md *MetaData) e(format string, args ...any) error {
f := "toml: "
if len(md.context) > 0 {
f = fmt.Sprintf("toml: (last key %q): ", md.context)
p := md.keyInfo[md.context.String()].pos
if p.Line > 0 {
f = fmt.Sprintf("toml: line %d (last key %q): ", p.Line, md.context)
}
}
return fmt.Errorf(f+format, args...)
}
// rvalue returns a reflect.Value of `v`. All pointers are resolved.
func rvalue(v any) reflect.Value {
return indirect(reflect.ValueOf(v))
}
// indirect returns the value pointed to by a pointer.
//
// Pointers are followed until the value is not a pointer. New values are
// allocated for each nil pointer.
//
// An exception to this rule is if the value satisfies an interface of interest
// to us (like encoding.TextUnmarshaler).
func indirect(v reflect.Value) reflect.Value {
if v.Kind() != reflect.Ptr {
if v.CanSet() {
pv := v.Addr()
pvi := pv.Interface()
if _, ok := pvi.(encoding.TextUnmarshaler); ok {
return pv
}
if _, ok := pvi.(Unmarshaler); ok {
return pv
}
}
return v
}
if v.IsNil() {
v.Set(reflect.New(v.Type().Elem()))
}
return indirect(reflect.Indirect(v))
}
func isUnifiable(rv reflect.Value) bool {
if rv.CanSet() {
return true
}
rvi := rv.Interface()
if _, ok := rvi.(encoding.TextUnmarshaler); ok {
return true
}
if _, ok := rvi.(Unmarshaler); ok {
return true
}
return false
}
// fmt %T with "interface {}" replaced with "any", which is far more readable.
func fmtType(t any) string {
return strings.ReplaceAll(fmt.Sprintf("%T", t), "interface {}", "any")
}
