Select Git revision
yaml.go 18.45 KiB
//
// Copyright (c) 2011-2019 Canonical Ltd
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// Package yaml implements YAML support for the Go language.
//
// Source code and other details for the project are available at GitHub:
//
// https://github.com/go-yaml/yaml
//
package yaml
import (
"errors"
"fmt"
"io"
"reflect"
"strings"
"sync"
"unicode/utf8"
)
// The Unmarshaler interface may be implemented by types to customize their
// behavior when being unmarshaled from a YAML document.
type Unmarshaler interface {
UnmarshalYAML(value *Node) error
}
type obsoleteUnmarshaler interface {
UnmarshalYAML(unmarshal func(interface{}) error) error
}
// The Marshaler interface may be implemented by types to customize their
// behavior when being marshaled into a YAML document. The returned value
// is marshaled in place of the original value implementing Marshaler.
//
// If an error is returned by MarshalYAML, the marshaling procedure stops
// and returns with the provided error.
type Marshaler interface {
MarshalYAML() (interface{}, error)
}
// Unmarshal decodes the first document found within the in byte slice
// and assigns decoded values into the out value.
//
// Maps and pointers (to a struct, string, int, etc) are accepted as out
// values. If an internal pointer within a struct is not initialized,
// the yaml package will initialize it if necessary for unmarshalling
// the provided data. The out parameter must not be nil.
//
// The type of the decoded values should be compatible with the respective
// values in out. If one or more values cannot be decoded due to a type
// mismatches, decoding continues partially until the end of the YAML
// content, and a *yaml.TypeError is returned with details for all
// missed values.
//
// Struct fields are only unmarshalled if they are exported (have an
// upper case first letter), and are unmarshalled using the field name
// lowercased as the default key. Custom keys may be defined via the// "yaml" name in the field tag: the content preceding the first comma
// is used as the key, and the following comma-separated options are
// used to tweak the marshalling process (see Marshal).
// Conflicting names result in a runtime error.
//
// For example:
//
// type T struct {
// F int `yaml:"a,omitempty"`
// B int
// }
// var t T
// yaml.Unmarshal([]byte("a: 1\nb: 2"), &t)
//
// See the documentation of Marshal for the format of tags and a list of
// supported tag options.
//
func Unmarshal(in []byte, out interface{}) (err error) {
return unmarshal(in, out, false)
}
// A Decorder reads and decodes YAML values from an input stream.
type Decoder struct {
parser *parser
knownFields bool
}
// NewDecoder returns a new decoder that reads from r.
//
// The decoder introduces its own buffering and may read
// data from r beyond the YAML values requested.
func NewDecoder(r io.Reader) *Decoder {
return &Decoder{
parser: newParserFromReader(r),
}
}
// KnownFields ensures that the keys in decoded mappings to
// exist as fields in the struct being decoded into.
func (dec *Decoder) KnownFields(enable bool) {
dec.knownFields = enable
}
// Decode reads the next YAML-encoded value from its input
// and stores it in the value pointed to by v.
//
// See the documentation for Unmarshal for details about the
// conversion of YAML into a Go value.
func (dec *Decoder) Decode(v interface{}) (err error) {
d := newDecoder()
d.knownFields = dec.knownFields
defer handleErr(&err)
node := dec.parser.parse()
if node == nil {
return io.EOF
}
out := reflect.ValueOf(v)
if out.Kind() == reflect.Ptr && !out.IsNil() {
out = out.Elem()
}
d.unmarshal(node, out)
if len(d.terrors) > 0 {
return &TypeError{d.terrors}
}
return nil
}
// Decode decodes the node and stores its data into the value pointed to by v.
//
// See the documentation for Unmarshal for details about the// conversion of YAML into a Go value.
func (n *Node) Decode(v interface{}) (err error) {
d := newDecoder()
defer handleErr(&err)
out := reflect.ValueOf(v)
if out.Kind() == reflect.Ptr && !out.IsNil() {
out = out.Elem()
}
d.unmarshal(n, out)
if len(d.terrors) > 0 {
return &TypeError{d.terrors}
}
return nil
}
func unmarshal(in []byte, out interface{}, strict bool) (err error) {
defer handleErr(&err)
d := newDecoder()
p := newParser(in)
defer p.destroy()
node := p.parse()
if node != nil {
v := reflect.ValueOf(out)
if v.Kind() == reflect.Ptr && !v.IsNil() {
v = v.Elem()
}
d.unmarshal(node, v)
}
if len(d.terrors) > 0 {
return &TypeError{d.terrors}
}
return nil
}
// Marshal serializes the value provided into a YAML document. The structure
// of the generated document will reflect the structure of the value itself.
// Maps and pointers (to struct, string, int, etc) are accepted as the in value.
//
// Struct fields are only marshalled if they are exported (have an upper case
// first letter), and are marshalled using the field name lowercased as the
// default key. Custom keys may be defined via the "yaml" name in the field
// tag: the content preceding the first comma is used as the key, and the
// following comma-separated options are used to tweak the marshalling process.
// Conflicting names result in a runtime error.
//
// The field tag format accepted is:
//
// `(...) yaml:"[<key>][,<flag1>[,<flag2>]]" (...)`
//
// The following flags are currently supported:
//
// omitempty Only include the field if it's not set to the zero
// value for the type or to empty slices or maps.
// Zero valued structs will be omitted if all their public
// fields are zero, unless they implement an IsZero
// method (see the IsZeroer interface type), in which
// case the field will be included if that method returns true.
//
// flow Marshal using a flow style (useful for structs,
// sequences and maps).
//
// inline Inline the field, which must be a struct or a map,
// causing all of its fields or keys to be processed as if
// they were part of the outer struct. For maps, keys must
// not conflict with the yaml keys of other struct fields.
//
// In addition, if the key is "-", the field is ignored.
//
// For example:
//// type T struct {
// F int `yaml:"a,omitempty"`
// B int
// }
// yaml.Marshal(&T{B: 2}) // Returns "b: 2\n"
// yaml.Marshal(&T{F: 1}} // Returns "a: 1\nb: 0\n"
//
func Marshal(in interface{}) (out []byte, err error) {
defer handleErr(&err)
e := newEncoder()
defer e.destroy()
e.marshalDoc("", reflect.ValueOf(in))
e.finish()
out = e.out
return
}
// An Encoder writes YAML values to an output stream.
type Encoder struct {
encoder *encoder
}
// NewEncoder returns a new encoder that writes to w.
// The Encoder should be closed after use to flush all data
// to w.
func NewEncoder(w io.Writer) *Encoder {
return &Encoder{
encoder: newEncoderWithWriter(w),
}
}
// Encode writes the YAML encoding of v to the stream.
// If multiple items are encoded to the stream, the
// second and subsequent document will be preceded
// with a "---" document separator, but the first will not.
//
// See the documentation for Marshal for details about the conversion of Go
// values to YAML.
func (e *Encoder) Encode(v interface{}) (err error) {
defer handleErr(&err)
e.encoder.marshalDoc("", reflect.ValueOf(v))
return nil
}
// SetIndent changes the used indentation used when encoding.
func (e *Encoder) SetIndent(spaces int) {
if spaces < 0 {
panic("yaml: cannot indent to a negative number of spaces")
}
e.encoder.indent = spaces
}
// Close closes the encoder by writing any remaining data.
// It does not write a stream terminating string "...".
func (e *Encoder) Close() (err error) {
defer handleErr(&err)
e.encoder.finish()
return nil
}
func handleErr(err *error) {
if v := recover(); v != nil {
if e, ok := v.(yamlError); ok {
*err = e.err
} else {
panic(v)
}
}
}
type yamlError struct {
err error
}
func fail(err error) {
panic(yamlError{err})
}
func failf(format string, args ...interface{}) {
panic(yamlError{fmt.Errorf("yaml: "+format, args...)})
}
// A TypeError is returned by Unmarshal when one or more fields in
// the YAML document cannot be properly decoded into the requested
// types. When this error is returned, the value is still
// unmarshaled partially.
type TypeError struct {
Errors []string
}
func (e *TypeError) Error() string {
return fmt.Sprintf("yaml: unmarshal errors:\n %s", strings.Join(e.Errors, "\n "))
}
type Kind uint32
const (
DocumentNode Kind = 1 << iota
SequenceNode
MappingNode
ScalarNode
AliasNode
)
type Style uint32
const (
TaggedStyle Style = 1 << iota
DoubleQuotedStyle
SingleQuotedStyle
LiteralStyle
FoldedStyle
FlowStyle
)
// Node represents an element in the YAML document hierarchy. While documents
// are typically encoded and decoded into higher level types, such as structs
// and maps, Node is an intermediate representation that allows detailed
// control over the content being decoded or encoded.
//
// Values that make use of the Node type interact with the yaml package in the
// same way any other type would do, by encoding and decoding yaml data
// directly or indirectly into them.
//
// For example:
//
// var person struct {
// Name string
// Address yaml.Node
// }
// err := yaml.Unmarshal(data, &person)
//
// Or by itself:
//
// var person Node
// err := yaml.Unmarshal(data, &person)
//
type Node struct {
// Kind defines whether the node is a document, a mapping, a sequence,
// a scalar value, or an alias to another node. The specific data type of // scalar nodes may be obtained via the ShortTag and LongTag methods.
Kind Kind
// Style allows customizing the apperance of the node in the tree.
Style Style
// Tag holds the YAML tag defining the data type for the value.
// When decoding, this field will always be set to the resolved tag,
// even when it wasn't explicitly provided in the YAML content.
// When encoding, if this field is unset the value type will be
// implied from the node properties, and if it is set, it will only
// be serialized into the representation if TaggedStyle is used or
// the implicit tag diverges from the provided one.
Tag string
// Value holds the unescaped and unquoted represenation of the value.
Value string
// Anchor holds the anchor name for this node, which allows aliases to point to it.
Anchor string
// Alias holds the node that this alias points to. Only valid when Kind is AliasNode.
Alias *Node
// Content holds contained nodes for documents, mappings, and sequences.
Content []*Node
// HeadComment holds any comments in the lines preceding the node and
// not separated by an empty line.
HeadComment string
// LineComment holds any comments at the end of the line where the node is in.
LineComment string
// FootComment holds any comments following the node and before empty lines.
FootComment string
// Line and Column hold the node position in the decoded YAML text.
// These fields are not respected when encoding the node.
Line int
Column int
}
// LongTag returns the long form of the tag that indicates the data type for
// the node. If the Tag field isn't explicitly defined, one will be computed
// based on the node properties.
func (n *Node) LongTag() string {
return longTag(n.ShortTag())
}
// ShortTag returns the short form of the YAML tag that indicates data type for
// the node. If the Tag field isn't explicitly defined, one will be computed
// based on the node properties.
func (n *Node) ShortTag() string {
if n.indicatedString() {
return strTag
}
if n.Tag == "" || n.Tag == "!" {
switch n.Kind {
case MappingNode:
return mapTag
case SequenceNode:
return seqTag
case AliasNode:
if n.Alias != nil {
return n.Alias.ShortTag()
}
case ScalarNode:
tag, _ := resolve("", n.Value)
return tag }
return ""
}
return shortTag(n.Tag)
}
func (n *Node) indicatedString() bool {
return n.Kind == ScalarNode &&
(shortTag(n.Tag) == strTag ||
(n.Tag == "" || n.Tag == "!") && n.Style&(SingleQuotedStyle|DoubleQuotedStyle|LiteralStyle|FoldedStyle) != 0)
}
// SetString is a convenience function that sets the node to a string value
// and defines its style in a pleasant way depending on its content.
func (n *Node) SetString(s string) {
n.Kind = ScalarNode
if utf8.ValidString(s) {
n.Value = s
n.Tag = strTag
} else {
n.Value = encodeBase64(s)
n.Tag = binaryTag
}
if strings.Contains(n.Value, "\n") {
n.Style = LiteralStyle
}
}
// --------------------------------------------------------------------------
// Maintain a mapping of keys to structure field indexes
// The code in this section was copied from mgo/bson.
// structInfo holds details for the serialization of fields of
// a given struct.
type structInfo struct {
FieldsMap map[string]fieldInfo
FieldsList []fieldInfo
// InlineMap is the number of the field in the struct that
// contains an ,inline map, or -1 if there's none.
InlineMap int
// InlineUnmarshalers holds indexes to inlined fields that
// contain unmarshaler values.
InlineUnmarshalers [][]int
}
type fieldInfo struct {
Key string
Num int
OmitEmpty bool
Flow bool
// Id holds the unique field identifier, so we can cheaply
// check for field duplicates without maintaining an extra map.
Id int
// Inline holds the field index if the field is part of an inlined struct.
Inline []int
}
var structMap = make(map[reflect.Type]*structInfo)
var fieldMapMutex sync.RWMutex
var unmarshalerType reflect.Type
func init() {
var v Unmarshaler
unmarshalerType = reflect.ValueOf(&v).Elem().Type()
}
func getStructInfo(st reflect.Type) (*structInfo, error) {
fieldMapMutex.RLock()
sinfo, found := structMap[st]
fieldMapMutex.RUnlock()
if found {
return sinfo, nil
}
n := st.NumField()
fieldsMap := make(map[string]fieldInfo)
fieldsList := make([]fieldInfo, 0, n)
inlineMap := -1
inlineUnmarshalers := [][]int(nil)
for i := 0; i != n; i++ {
field := st.Field(i)
if field.PkgPath != "" && !field.Anonymous {
continue // Private field
}
info := fieldInfo{Num: i}
tag := field.Tag.Get("yaml")
if tag == "" && strings.Index(string(field.Tag), ":") < 0 {
tag = string(field.Tag)
}
if tag == "-" {
continue
}
inline := false
fields := strings.Split(tag, ",")
if len(fields) > 1 {
for _, flag := range fields[1:] {
switch flag {
case "omitempty":
info.OmitEmpty = true
case "flow":
info.Flow = true
case "inline":
inline = true
default:
return nil, errors.New(fmt.Sprintf("unsupported flag %q in tag %q of type %s", flag, tag, st))
}
}
tag = fields[0]
}
if inline {
switch field.Type.Kind() {
case reflect.Map:
if inlineMap >= 0 {
return nil, errors.New("multiple ,inline maps in struct " + st.String())
}
if field.Type.Key() != reflect.TypeOf("") {
return nil, errors.New("option ,inline needs a map with string keys in struct " + st.String())
}
inlineMap = info.Num
case reflect.Struct, reflect.Ptr:
ftype := field.Type
for ftype.Kind() == reflect.Ptr {
ftype = ftype.Elem()
}
if ftype.Kind() != reflect.Struct {
return nil, errors.New("option ,inline may only be used on a struct or map field")
}
if reflect.PtrTo(ftype).Implements(unmarshalerType) {
inlineUnmarshalers = append(inlineUnmarshalers, []int{i})
} else {
sinfo, err := getStructInfo(ftype)
if err != nil { return nil, err
}
for _, index := range sinfo.InlineUnmarshalers {
inlineUnmarshalers = append(inlineUnmarshalers, append([]int{i}, index...))
}
for _, finfo := range sinfo.FieldsList {
if _, found := fieldsMap[finfo.Key]; found {
msg := "duplicated key '" + finfo.Key + "' in struct " + st.String()
return nil, errors.New(msg)
}
if finfo.Inline == nil {
finfo.Inline = []int{i, finfo.Num}
} else {
finfo.Inline = append([]int{i}, finfo.Inline...)
}
finfo.Id = len(fieldsList)
fieldsMap[finfo.Key] = finfo
fieldsList = append(fieldsList, finfo)
}
}
default:
return nil, errors.New("option ,inline may only be used on a struct or map field")
}
continue
}
if tag != "" {
info.Key = tag
} else {
info.Key = strings.ToLower(field.Name)
}
if _, found = fieldsMap[info.Key]; found {
msg := "duplicated key '" + info.Key + "' in struct " + st.String()
return nil, errors.New(msg)
}
info.Id = len(fieldsList)
fieldsList = append(fieldsList, info)
fieldsMap[info.Key] = info
}
sinfo = &structInfo{
FieldsMap: fieldsMap,
FieldsList: fieldsList,
InlineMap: inlineMap,
InlineUnmarshalers: inlineUnmarshalers,
}
fieldMapMutex.Lock()
structMap[st] = sinfo
fieldMapMutex.Unlock()
return sinfo, nil
}
// IsZeroer is used to check whether an object is zero to
// determine whether it should be omitted when marshaling
// with the omitempty flag. One notable implementation
// is time.Time.
type IsZeroer interface {
IsZero() bool
}
func isZero(v reflect.Value) bool {
kind := v.Kind()
if z, ok := v.Interface().(IsZeroer); ok {
if (kind == reflect.Ptr || kind == reflect.Interface) && v.IsNil() {
return true
}
return z.IsZero() }
switch kind {
case reflect.String:
return len(v.String()) == 0
case reflect.Interface, reflect.Ptr:
return v.IsNil()
case reflect.Slice:
return v.Len() == 0
case reflect.Map:
return v.Len() == 0
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
return v.Int() == 0
case reflect.Float32, reflect.Float64:
return v.Float() == 0
case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
return v.Uint() == 0
case reflect.Bool:
return !v.Bool()
case reflect.Struct:
vt := v.Type()
for i := v.NumField() - 1; i >= 0; i-- {
if vt.Field(i).PkgPath != "" {
continue // Private field
}
if !isZero(v.Field(i)) {
return false
}
}
return true
}
return false
}