// 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" ) // MapSlice encodes and decodes as a YAML map. // The order of keys is preserved when encoding and decoding. type MapSlice []MapItem // MapItem is an item in a MapSlice. type MapItem struct { Key, Value interface{} } // The Unmarshaler interface may be implemented by types to customize their // behavior when being unmarshaled from a YAML document. The UnmarshalYAML // method receives a function that may be called to unmarshal the original // YAML value into a field or variable. It is safe to call the unmarshal // function parameter more than once if necessary. type Unmarshaler 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) } // UnmarshalStrict is like Unmarshal except that any fields that are found // in the data that do not have corresponding struct members, or mapping // keys that are duplicates, will result in // an error. func UnmarshalStrict(in []byte, out interface{}) (err error) { return unmarshal(in, out, true) } // A Decoder reads and decodes YAML values from an input stream. type Decoder struct { strict bool parser *parser } // 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), } } // SetStrict sets whether strict decoding behaviour is enabled when // decoding items in the data (see UnmarshalStrict). By default, decoding is not strict. func (dec *Decoder) SetStrict(strict bool) { dec.strict = strict } // 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(dec.strict) 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 } func unmarshal(in []byte, out interface{}, strict bool) (err error) { defer handleErr(&err) d := newDecoder(strict) 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 } // 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 ")) } // -------------------------------------------------------------------------- // 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 } 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 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 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: sinfo, err := getStructInfo(field.Type) if err != nil { return nil, err } 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 needs a struct value or map field") return nil, errors.New("Option ,inline needs a struct value 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, } 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 }