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// Copyright 2013 Dario Castañé. All rights reserved.
// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Based on src/pkg/reflect/deepequal.go from official
// golang's stdlib.
package mergo
import (
"fmt"
"reflect"
)
func hasExportedField(dst reflect.Value) (exported bool) {
for i, n := 0, dst.NumField(); i < n; i++ {
field := dst.Type().Field(i)
if field.Anonymous && dst.Field(i).Kind() == reflect.Struct {
exported = exported || hasExportedField(dst.Field(i))
} else {
exported = exported || len(field.PkgPath) == 0
}
}
return
}
type Config struct {
Overwrite bool
AppendSlice bool
Transformers Transformers
}
type Transformers interface {
Transformer(reflect.Type) func(dst, src reflect.Value) error
}
// Traverses recursively both values, assigning src's fields values to dst.
// The map argument tracks comparisons that have already been seen, which allows
// short circuiting on recursive types.
func deepMerge(dst, src reflect.Value, visited map[uintptr]*visit, depth int, config *Config) (err error) {
overwrite := config.Overwrite
if !src.IsValid() {
return
}
if dst.CanAddr() {
addr := dst.UnsafeAddr()
h := 17 * addr
seen := visited[h]
typ := dst.Type()
for p := seen; p != nil; p = p.next {
if p.ptr == addr && p.typ == typ {
return nil
}
}
// Remember, remember...
visited[h] = &visit{addr, typ, seen}
}
if config.Transformers != nil && !isEmptyValue(dst) {
if fn := config.Transformers.Transformer(dst.Type()); fn != nil {
err = fn(dst, src)
return
}
}
switch dst.Kind() {
case reflect.Struct:
if hasExportedField(dst) {
for i, n := 0, dst.NumField(); i < n; i++ {
if err = deepMerge(dst.Field(i), src.Field(i), visited, depth+1, config); err != nil {
return
}
}
} else {
if dst.CanSet() && !isEmptyValue(src) && (overwrite || isEmptyValue(dst)) {
dst.Set(src)
}
}
case reflect.Map:
if dst.IsNil() && !src.IsNil() {
dst.Set(reflect.MakeMap(dst.Type()))
}
for _, key := range src.MapKeys() {
srcElement := src.MapIndex(key)
if !srcElement.IsValid() {
continue
}
dstElement := dst.MapIndex(key)
switch srcElement.Kind() {
case reflect.Chan, reflect.Func, reflect.Map, reflect.Interface, reflect.Slice:
if srcElement.IsNil() {
continue
}
fallthrough
default:
if !srcElement.CanInterface() {
continue
}
switch reflect.TypeOf(srcElement.Interface()).Kind() {
case reflect.Struct:
fallthrough
case reflect.Ptr:
fallthrough
case reflect.Map:
srcMapElm := srcElement
dstMapElm := dstElement
if srcMapElm.CanInterface() {
srcMapElm = reflect.ValueOf(srcMapElm.Interface())
if dstMapElm.IsValid() {
dstMapElm = reflect.ValueOf(dstMapElm.Interface())
}
}
if err = deepMerge(dstMapElm, srcMapElm, visited, depth+1, config); err != nil {
return
}
case reflect.Slice:
srcSlice := reflect.ValueOf(srcElement.Interface())
var dstSlice reflect.Value
if !dstElement.IsValid() || dstElement.IsNil() {
dstSlice = reflect.MakeSlice(srcSlice.Type(), 0, srcSlice.Len())
} else {
dstSlice = reflect.ValueOf(dstElement.Interface())
}
if !isEmptyValue(src) && (overwrite || isEmptyValue(dst)) && !config.AppendSlice {
dstSlice = srcSlice
} else if config.AppendSlice {
if srcSlice.Type() != dstSlice.Type() {
return fmt.Errorf("cannot append two slice with different type (%s, %s)", srcSlice.Type(), dstSlice.Type())
}
dstSlice = reflect.AppendSlice(dstSlice, srcSlice)
}
dst.SetMapIndex(key, dstSlice)
}
}
if dstElement.IsValid() && reflect.TypeOf(srcElement.Interface()).Kind() == reflect.Map {
continue
}
if srcElement.IsValid() && (overwrite || (!dstElement.IsValid() || isEmptyValue(dstElement))) {
if dst.IsNil() {
dst.Set(reflect.MakeMap(dst.Type()))
}
dst.SetMapIndex(key, srcElement)
}
}
case reflect.Slice:
if !dst.CanSet() {
break
}
if !isEmptyValue(src) && (overwrite || isEmptyValue(dst)) && !config.AppendSlice {
dst.Set(src)
} else if config.AppendSlice {
if src.Type() != dst.Type() {
return fmt.Errorf("cannot append two slice with different type (%s, %s)", src.Type(), dst.Type())
}
dst.Set(reflect.AppendSlice(dst, src))
}
case reflect.Ptr:
fallthrough
case reflect.Interface:
if src.IsNil() {
break
}
if src.Kind() != reflect.Interface {
if dst.IsNil() || overwrite {
if dst.CanSet() && (overwrite || isEmptyValue(dst)) {
dst.Set(src)
}
} else if src.Kind() == reflect.Ptr {
if err = deepMerge(dst.Elem(), src.Elem(), visited, depth+1, config); err != nil {
return
}
} else if dst.Elem().Type() == src.Type() {
if err = deepMerge(dst.Elem(), src, visited, depth+1, config); err != nil {
return
}
} else {
return ErrDifferentArgumentsTypes
}
break
}
if dst.IsNil() || overwrite {
if dst.CanSet() && (overwrite || isEmptyValue(dst)) {
dst.Set(src)
}
} else if err = deepMerge(dst.Elem(), src.Elem(), visited, depth+1, config); err != nil {
return
}
default:
if dst.CanSet() && !isEmptyValue(src) && (overwrite || isEmptyValue(dst)) {
dst.Set(src)
}
}
return
}
// Merge will fill any empty for value type attributes on the dst struct using corresponding
// src attributes if they themselves are not empty. dst and src must be valid same-type structs
// and dst must be a pointer to struct.
// It won't merge unexported (private) fields and will do recursively any exported field.
func Merge(dst, src interface{}, opts ...func(*Config)) error {
return merge(dst, src, opts...)
}
// MergeWithOverwrite will do the same as Merge except that non-empty dst attributes will be overriden by
// non-empty src attribute values.
// Deprecated: use Merge(…) with WithOverride
func MergeWithOverwrite(dst, src interface{}, opts ...func(*Config)) error {
return merge(dst, src, append(opts, WithOverride)...)
}
// WithTransformers adds transformers to merge, allowing to customize the merging of some types.
func WithTransformers(transformers Transformers) func(*Config) {
return func(config *Config) {
config.Transformers = transformers
}
}
// WithOverride will make merge override non-empty dst attributes with non-empty src attributes values.
func WithOverride(config *Config) {
config.Overwrite = true
}
// WithAppendSlice will make merge append slices instead of overwriting it
func WithAppendSlice(config *Config) {
config.AppendSlice = true
}
func merge(dst, src interface{}, opts ...func(*Config)) error {
var (
vDst, vSrc reflect.Value
err error
)
config := &Config{}
for _, opt := range opts {
opt(config)
}
if vDst, vSrc, err = resolveValues(dst, src); err != nil {
return err
}
if vDst.Type() != vSrc.Type() {
return ErrDifferentArgumentsTypes
}
return deepMerge(vDst, vSrc, make(map[uintptr]*visit), 0, config)
}