peridot/vendor/go.mongodb.org/mongo-driver/bson/bsoncodec/struct_codec.go

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2022-07-07 20:11:50 +00:00
// Copyright (C) MongoDB, Inc. 2017-present.
//
// 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
package bsoncodec
import (
"errors"
"fmt"
"reflect"
"sort"
"strings"
"sync"
"time"
"go.mongodb.org/mongo-driver/bson/bsonoptions"
"go.mongodb.org/mongo-driver/bson/bsonrw"
"go.mongodb.org/mongo-driver/bson/bsontype"
)
// DecodeError represents an error that occurs when unmarshalling BSON bytes into a native Go type.
type DecodeError struct {
keys []string
wrapped error
}
// Unwrap returns the underlying error
func (de *DecodeError) Unwrap() error {
return de.wrapped
}
// Error implements the error interface.
func (de *DecodeError) Error() string {
// The keys are stored in reverse order because the de.keys slice is builtup while propagating the error up the
// stack of BSON keys, so we call de.Keys(), which reverses them.
keyPath := strings.Join(de.Keys(), ".")
return fmt.Sprintf("error decoding key %s: %v", keyPath, de.wrapped)
}
// Keys returns the BSON key path that caused an error as a slice of strings. The keys in the slice are in top-down
// order. For example, if the document being unmarshalled was {a: {b: {c: 1}}} and the value for c was supposed to be
// a string, the keys slice will be ["a", "b", "c"].
func (de *DecodeError) Keys() []string {
reversedKeys := make([]string, 0, len(de.keys))
for idx := len(de.keys) - 1; idx >= 0; idx-- {
reversedKeys = append(reversedKeys, de.keys[idx])
}
return reversedKeys
}
// Zeroer allows custom struct types to implement a report of zero
// state. All struct types that don't implement Zeroer or where IsZero
// returns false are considered to be not zero.
type Zeroer interface {
IsZero() bool
}
// StructCodec is the Codec used for struct values.
type StructCodec struct {
cache map[reflect.Type]*structDescription
l sync.RWMutex
parser StructTagParser
DecodeZeroStruct bool
DecodeDeepZeroInline bool
EncodeOmitDefaultStruct bool
AllowUnexportedFields bool
OverwriteDuplicatedInlinedFields bool
}
var _ ValueEncoder = &StructCodec{}
var _ ValueDecoder = &StructCodec{}
// NewStructCodec returns a StructCodec that uses p for struct tag parsing.
func NewStructCodec(p StructTagParser, opts ...*bsonoptions.StructCodecOptions) (*StructCodec, error) {
if p == nil {
return nil, errors.New("a StructTagParser must be provided to NewStructCodec")
}
structOpt := bsonoptions.MergeStructCodecOptions(opts...)
codec := &StructCodec{
cache: make(map[reflect.Type]*structDescription),
parser: p,
}
if structOpt.DecodeZeroStruct != nil {
codec.DecodeZeroStruct = *structOpt.DecodeZeroStruct
}
if structOpt.DecodeDeepZeroInline != nil {
codec.DecodeDeepZeroInline = *structOpt.DecodeDeepZeroInline
}
if structOpt.EncodeOmitDefaultStruct != nil {
codec.EncodeOmitDefaultStruct = *structOpt.EncodeOmitDefaultStruct
}
if structOpt.OverwriteDuplicatedInlinedFields != nil {
codec.OverwriteDuplicatedInlinedFields = *structOpt.OverwriteDuplicatedInlinedFields
}
if structOpt.AllowUnexportedFields != nil {
codec.AllowUnexportedFields = *structOpt.AllowUnexportedFields
}
return codec, nil
}
// EncodeValue handles encoding generic struct types.
func (sc *StructCodec) EncodeValue(r EncodeContext, vw bsonrw.ValueWriter, val reflect.Value) error {
if !val.IsValid() || val.Kind() != reflect.Struct {
return ValueEncoderError{Name: "StructCodec.EncodeValue", Kinds: []reflect.Kind{reflect.Struct}, Received: val}
}
sd, err := sc.describeStruct(r.Registry, val.Type())
if err != nil {
return err
}
dw, err := vw.WriteDocument()
if err != nil {
return err
}
var rv reflect.Value
for _, desc := range sd.fl {
if desc.inline == nil {
rv = val.Field(desc.idx)
} else {
rv, err = fieldByIndexErr(val, desc.inline)
if err != nil {
continue
}
}
desc.encoder, rv, err = defaultValueEncoders.lookupElementEncoder(r, desc.encoder, rv)
if err != nil && err != errInvalidValue {
return err
}
if err == errInvalidValue {
if desc.omitEmpty {
continue
}
vw2, err := dw.WriteDocumentElement(desc.name)
if err != nil {
return err
}
err = vw2.WriteNull()
if err != nil {
return err
}
continue
}
if desc.encoder == nil {
return ErrNoEncoder{Type: rv.Type()}
}
encoder := desc.encoder
var isZero bool
rvInterface := rv.Interface()
if cz, ok := encoder.(CodecZeroer); ok {
isZero = cz.IsTypeZero(rvInterface)
} else if rv.Kind() == reflect.Interface {
// sc.isZero will not treat an interface rv as an interface, so we need to check for the zero interface separately.
isZero = rv.IsNil()
} else {
isZero = sc.isZero(rvInterface)
}
if desc.omitEmpty && isZero {
continue
}
vw2, err := dw.WriteDocumentElement(desc.name)
if err != nil {
return err
}
ectx := EncodeContext{Registry: r.Registry, MinSize: desc.minSize}
err = encoder.EncodeValue(ectx, vw2, rv)
if err != nil {
return err
}
}
if sd.inlineMap >= 0 {
rv := val.Field(sd.inlineMap)
collisionFn := func(key string) bool {
_, exists := sd.fm[key]
return exists
}
return defaultMapCodec.mapEncodeValue(r, dw, rv, collisionFn)
}
return dw.WriteDocumentEnd()
}
func newDecodeError(key string, original error) error {
de, ok := original.(*DecodeError)
if !ok {
return &DecodeError{
keys: []string{key},
wrapped: original,
}
}
de.keys = append(de.keys, key)
return de
}
// DecodeValue implements the Codec interface.
// By default, map types in val will not be cleared. If a map has existing key/value pairs, it will be extended with the new ones from vr.
// For slices, the decoder will set the length of the slice to zero and append all elements. The underlying array will not be cleared.
func (sc *StructCodec) DecodeValue(r DecodeContext, vr bsonrw.ValueReader, val reflect.Value) error {
if !val.CanSet() || val.Kind() != reflect.Struct {
return ValueDecoderError{Name: "StructCodec.DecodeValue", Kinds: []reflect.Kind{reflect.Struct}, Received: val}
}
switch vrType := vr.Type(); vrType {
case bsontype.Type(0), bsontype.EmbeddedDocument:
case bsontype.Null:
if err := vr.ReadNull(); err != nil {
return err
}
val.Set(reflect.Zero(val.Type()))
return nil
case bsontype.Undefined:
if err := vr.ReadUndefined(); err != nil {
return err
}
val.Set(reflect.Zero(val.Type()))
return nil
default:
return fmt.Errorf("cannot decode %v into a %s", vrType, val.Type())
}
sd, err := sc.describeStruct(r.Registry, val.Type())
if err != nil {
return err
}
if sc.DecodeZeroStruct {
val.Set(reflect.Zero(val.Type()))
}
if sc.DecodeDeepZeroInline && sd.inline {
val.Set(deepZero(val.Type()))
}
var decoder ValueDecoder
var inlineMap reflect.Value
if sd.inlineMap >= 0 {
inlineMap = val.Field(sd.inlineMap)
decoder, err = r.LookupDecoder(inlineMap.Type().Elem())
if err != nil {
return err
}
}
dr, err := vr.ReadDocument()
if err != nil {
return err
}
for {
name, vr, err := dr.ReadElement()
if err == bsonrw.ErrEOD {
break
}
if err != nil {
return err
}
fd, exists := sd.fm[name]
if !exists {
// if the original name isn't found in the struct description, try again with the name in lowercase
// this could match if a BSON tag isn't specified because by default, describeStruct lowercases all field
// names
fd, exists = sd.fm[strings.ToLower(name)]
}
if !exists {
if sd.inlineMap < 0 {
// The encoding/json package requires a flag to return on error for non-existent fields.
// This functionality seems appropriate for the struct codec.
err = vr.Skip()
if err != nil {
return err
}
continue
}
if inlineMap.IsNil() {
inlineMap.Set(reflect.MakeMap(inlineMap.Type()))
}
elem := reflect.New(inlineMap.Type().Elem()).Elem()
r.Ancestor = inlineMap.Type()
err = decoder.DecodeValue(r, vr, elem)
if err != nil {
return err
}
inlineMap.SetMapIndex(reflect.ValueOf(name), elem)
continue
}
var field reflect.Value
if fd.inline == nil {
field = val.Field(fd.idx)
} else {
field, err = getInlineField(val, fd.inline)
if err != nil {
return err
}
}
if !field.CanSet() { // Being settable is a super set of being addressable.
innerErr := fmt.Errorf("field %v is not settable", field)
return newDecodeError(fd.name, innerErr)
}
if field.Kind() == reflect.Ptr && field.IsNil() {
field.Set(reflect.New(field.Type().Elem()))
}
field = field.Addr()
dctx := DecodeContext{Registry: r.Registry, Truncate: fd.truncate || r.Truncate}
if fd.decoder == nil {
return newDecodeError(fd.name, ErrNoDecoder{Type: field.Elem().Type()})
}
if decoder, ok := fd.decoder.(ValueDecoder); ok {
err = decoder.DecodeValue(dctx, vr, field.Elem())
if err != nil {
return newDecodeError(fd.name, err)
}
continue
}
err = fd.decoder.DecodeValue(dctx, vr, field)
if err != nil {
return newDecodeError(fd.name, err)
}
}
return nil
}
func (sc *StructCodec) isZero(i interface{}) bool {
v := reflect.ValueOf(i)
// check the value validity
if !v.IsValid() {
return true
}
if z, ok := v.Interface().(Zeroer); ok && (v.Kind() != reflect.Ptr || !v.IsNil()) {
return z.IsZero()
}
switch v.Kind() {
case reflect.Array, reflect.Map, reflect.Slice, reflect.String:
return v.Len() == 0
case reflect.Bool:
return !v.Bool()
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
return v.Int() == 0
case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
return v.Uint() == 0
case reflect.Float32, reflect.Float64:
return v.Float() == 0
case reflect.Interface, reflect.Ptr:
return v.IsNil()
case reflect.Struct:
if sc.EncodeOmitDefaultStruct {
vt := v.Type()
if vt == tTime {
return v.Interface().(time.Time).IsZero()
}
for i := 0; i < v.NumField(); i++ {
if vt.Field(i).PkgPath != "" && !vt.Field(i).Anonymous {
continue // Private field
}
fld := v.Field(i)
if !sc.isZero(fld.Interface()) {
return false
}
}
return true
}
}
return false
}
type structDescription struct {
fm map[string]fieldDescription
fl []fieldDescription
inlineMap int
inline bool
}
type fieldDescription struct {
name string // BSON key name
fieldName string // struct field name
idx int
omitEmpty bool
minSize bool
truncate bool
inline []int
encoder ValueEncoder
decoder ValueDecoder
}
type byIndex []fieldDescription
func (bi byIndex) Len() int { return len(bi) }
func (bi byIndex) Swap(i, j int) { bi[i], bi[j] = bi[j], bi[i] }
func (bi byIndex) Less(i, j int) bool {
// If a field is inlined, its index in the top level struct is stored at inline[0]
iIdx, jIdx := bi[i].idx, bi[j].idx
if len(bi[i].inline) > 0 {
iIdx = bi[i].inline[0]
}
if len(bi[j].inline) > 0 {
jIdx = bi[j].inline[0]
}
if iIdx != jIdx {
return iIdx < jIdx
}
for k, biik := range bi[i].inline {
if k >= len(bi[j].inline) {
return false
}
if biik != bi[j].inline[k] {
return biik < bi[j].inline[k]
}
}
return len(bi[i].inline) < len(bi[j].inline)
}
func (sc *StructCodec) describeStruct(r *Registry, t reflect.Type) (*structDescription, error) {
// We need to analyze the struct, including getting the tags, collecting
// information about inlining, and create a map of the field name to the field.
sc.l.RLock()
ds, exists := sc.cache[t]
sc.l.RUnlock()
if exists {
return ds, nil
}
numFields := t.NumField()
sd := &structDescription{
fm: make(map[string]fieldDescription, numFields),
fl: make([]fieldDescription, 0, numFields),
inlineMap: -1,
}
var fields []fieldDescription
for i := 0; i < numFields; i++ {
sf := t.Field(i)
if sf.PkgPath != "" && (!sc.AllowUnexportedFields || !sf.Anonymous) {
// field is private or unexported fields aren't allowed, ignore
continue
}
sfType := sf.Type
encoder, err := r.LookupEncoder(sfType)
if err != nil {
encoder = nil
}
decoder, err := r.LookupDecoder(sfType)
if err != nil {
decoder = nil
}
description := fieldDescription{
fieldName: sf.Name,
idx: i,
encoder: encoder,
decoder: decoder,
}
stags, err := sc.parser.ParseStructTags(sf)
if err != nil {
return nil, err
}
if stags.Skip {
continue
}
description.name = stags.Name
description.omitEmpty = stags.OmitEmpty
description.minSize = stags.MinSize
description.truncate = stags.Truncate
if stags.Inline {
sd.inline = true
switch sfType.Kind() {
case reflect.Map:
if sd.inlineMap >= 0 {
return nil, errors.New("(struct " + t.String() + ") multiple inline maps")
}
if sfType.Key() != tString {
return nil, errors.New("(struct " + t.String() + ") inline map must have a string keys")
}
sd.inlineMap = description.idx
case reflect.Ptr:
sfType = sfType.Elem()
if sfType.Kind() != reflect.Struct {
return nil, fmt.Errorf("(struct %s) inline fields must be a struct, a struct pointer, or a map", t.String())
}
fallthrough
case reflect.Struct:
inlinesf, err := sc.describeStruct(r, sfType)
if err != nil {
return nil, err
}
for _, fd := range inlinesf.fl {
if fd.inline == nil {
fd.inline = []int{i, fd.idx}
} else {
fd.inline = append([]int{i}, fd.inline...)
}
fields = append(fields, fd)
}
default:
return nil, fmt.Errorf("(struct %s) inline fields must be a struct, a struct pointer, or a map", t.String())
}
continue
}
fields = append(fields, description)
}
// Sort fieldDescriptions by name and use dominance rules to determine which should be added for each name
sort.Slice(fields, func(i, j int) bool {
x := fields
// sort field by name, breaking ties with depth, then
// breaking ties with index sequence.
if x[i].name != x[j].name {
return x[i].name < x[j].name
}
if len(x[i].inline) != len(x[j].inline) {
return len(x[i].inline) < len(x[j].inline)
}
return byIndex(x).Less(i, j)
})
for advance, i := 0, 0; i < len(fields); i += advance {
// One iteration per name.
// Find the sequence of fields with the name of this first field.
fi := fields[i]
name := fi.name
for advance = 1; i+advance < len(fields); advance++ {
fj := fields[i+advance]
if fj.name != name {
break
}
}
if advance == 1 { // Only one field with this name
sd.fl = append(sd.fl, fi)
sd.fm[name] = fi
continue
}
dominant, ok := dominantField(fields[i : i+advance])
if !ok || !sc.OverwriteDuplicatedInlinedFields {
return nil, fmt.Errorf("struct %s) duplicated key %s", t.String(), name)
}
sd.fl = append(sd.fl, dominant)
sd.fm[name] = dominant
}
sort.Sort(byIndex(sd.fl))
sc.l.Lock()
sc.cache[t] = sd
sc.l.Unlock()
return sd, nil
}
// dominantField looks through the fields, all of which are known to
// have the same name, to find the single field that dominates the
// others using Go's inlining rules. If there are multiple top-level
// fields, the boolean will be false: This condition is an error in Go
// and we skip all the fields.
func dominantField(fields []fieldDescription) (fieldDescription, bool) {
// The fields are sorted in increasing index-length order, then by presence of tag.
// That means that the first field is the dominant one. We need only check
// for error cases: two fields at top level.
if len(fields) > 1 &&
len(fields[0].inline) == len(fields[1].inline) {
return fieldDescription{}, false
}
return fields[0], true
}
func fieldByIndexErr(v reflect.Value, index []int) (result reflect.Value, err error) {
defer func() {
if recovered := recover(); recovered != nil {
switch r := recovered.(type) {
case string:
err = fmt.Errorf("%s", r)
case error:
err = r
}
}
}()
result = v.FieldByIndex(index)
return
}
func getInlineField(val reflect.Value, index []int) (reflect.Value, error) {
field, err := fieldByIndexErr(val, index)
if err == nil {
return field, nil
}
// if parent of this element doesn't exist, fix its parent
inlineParent := index[:len(index)-1]
var fParent reflect.Value
if fParent, err = fieldByIndexErr(val, inlineParent); err != nil {
fParent, err = getInlineField(val, inlineParent)
if err != nil {
return fParent, err
}
}
fParent.Set(reflect.New(fParent.Type().Elem()))
return fieldByIndexErr(val, index)
}
// DeepZero returns recursive zero object
func deepZero(st reflect.Type) (result reflect.Value) {
result = reflect.Indirect(reflect.New(st))
if result.Kind() == reflect.Struct {
for i := 0; i < result.NumField(); i++ {
if f := result.Field(i); f.Kind() == reflect.Ptr {
if f.CanInterface() {
if ft := reflect.TypeOf(f.Interface()); ft.Elem().Kind() == reflect.Struct {
result.Field(i).Set(recursivePointerTo(deepZero(ft.Elem())))
}
}
}
}
}
return
}
// recursivePointerTo calls reflect.New(v.Type) but recursively for its fields inside
func recursivePointerTo(v reflect.Value) reflect.Value {
v = reflect.Indirect(v)
result := reflect.New(v.Type())
if v.Kind() == reflect.Struct {
for i := 0; i < v.NumField(); i++ {
if f := v.Field(i); f.Kind() == reflect.Ptr {
if f.Elem().Kind() == reflect.Struct {
result.Elem().Field(i).Set(recursivePointerTo(f))
}
}
}
}
return result
}