/
mapper_decode.go
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/
mapper_decode.go
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// Copyright 2016-2018, Pulumi Corporation.
//
// 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 mapper
import (
"encoding"
"fmt"
"reflect"
"github.com/pkg/errors"
"github.com/pulumi/pulumi/sdk/v3/go/common/util/contract"
)
// Decoder is a func that knows how to decode into particular type.
type Decoder func(m Mapper, obj map[string]interface{}) (interface{}, error)
// Decoders is a map from type to a decoder func that understands how to decode that type.
type Decoders map[reflect.Type]Decoder
// Decode decodes an entire map into a target object, using tag-directed mappings.
func (md *mapper) Decode(obj map[string]interface{}, target interface{}) MappingError {
// Fetch the destination types and validate that we can store into the target (i.e., a valid lval).
vdst := reflect.ValueOf(target)
contract.Assertf(vdst.Kind() == reflect.Ptr && !vdst.IsNil() && vdst.Elem().CanSet(),
"Target %v must be a non-nil, settable pointer", vdst.Type())
vdstType := vdst.Type().Elem()
contract.Assertf(vdstType.Kind() == reflect.Struct && !vdst.IsNil(),
"Target %v must be a struct type with `pulumi:\"x\"` tags to direct decoding", vdstType)
// Keep track of any errors that result.
var errs []error
// For each field in the struct that has a `pulumi:"name"`, look it up in the map by that `name`, issuing an error
// if it is missing or of the wrong type. For each field that is marked optional, e.g. `pulumi:"name,optional"`,
// do the same, but permit it to be missing without issuing an error.
flds := make(map[string]bool)
for _, fldtag := range md.structFieldsTags(vdstType) {
// Use the tag to direct unmarshaling.
key := fldtag.Key
if !fldtag.Skip {
fld := vdst.Elem().FieldByName(fldtag.Info.Name)
if err := md.DecodeValue(obj, vdstType, key, fld.Addr().Interface(), fldtag.Optional); err != nil {
errs = append(errs, err)
}
}
// Remember this key so we can be sure not to reject it later when checking for unrecognized fields.
flds[key] = true
}
// Afterwards, if there are any unrecognized fields, issue an error.
if !md.opts.IgnoreUnrecognized {
for k := range obj {
if !flds[k] {
err := NewUnrecognizedError(vdstType, k)
errs = append(errs, err)
}
}
}
// If there are no errors, return nil; else manufacture a decode error object.
if len(errs) == 0 {
return nil
}
return NewMappingError(errs)
}
// DecodeValue decodes primitive type fields. For fields of complex types, we use custom deserialization.
func (md *mapper) DecodeValue(obj map[string]interface{}, ty reflect.Type, key string,
target interface{}, optional bool) FieldError {
vdst := reflect.ValueOf(target)
contract.Assertf(vdst.Kind() == reflect.Ptr && !vdst.IsNil() && vdst.Elem().CanSet(),
"Target %v must be a non-nil, settable pointer", vdst.Type())
if v, has := obj[key]; has {
// The field exists; okay, try to map it to the right type.
vsrc := reflect.ValueOf(v)
// Ensure the source is valid; this is false if the value reflects the zero value.
if vsrc.IsValid() {
vdstType := vdst.Type().Elem()
// So long as the target element is a pointer, we have a pointer to pointer; dig through until we bottom out
// on the non-pointer type that matches the source. This assumes the source isn't itself a pointer!
contract.Assertf(vsrc.Type().Kind() != reflect.Ptr, "source is a pointer")
for vdstType.Kind() == reflect.Ptr {
vdst = vdst.Elem()
vdstType = vdstType.Elem()
if !vdst.Elem().CanSet() {
// If the pointer is nil, initialize it so we can set it below.
contract.Assert(vdst.IsNil())
vdst.Set(reflect.New(vdstType))
}
}
// Adjust the value if necessary; this handles recursive struct marshaling, interface unboxing, and more.
var err FieldError
if vsrc, err = md.adjustValueForAssignment(vsrc, vdstType, ty, key); err != nil {
return err
}
// Finally, provided everything is kosher, go ahead and store the value; otherwise, issue an error.
if vsrc.Type().AssignableTo(vdstType) {
vdst.Elem().Set(vsrc)
return nil
}
return NewWrongTypeError(ty, key, vdstType, vsrc.Type())
}
}
if !optional && !md.opts.IgnoreMissing {
// The field doesn't exist and yet it is required; issue an error.
return NewMissingError(ty, key)
}
return nil
}
var (
emptyObject = map[string]interface{}{}
textUnmarshalerType = reflect.TypeOf(new(encoding.TextUnmarshaler)).Elem()
)
// adjustValueForAssignment converts if possible to produce the target type.
func (md *mapper) adjustValueForAssignment(val reflect.Value,
to reflect.Type, ty reflect.Type, key string) (reflect.Value, FieldError) {
for !val.Type().AssignableTo(to) {
// The source cannot be assigned directly to the destination. Go through all known conversions.
if val.Type().ConvertibleTo(to) {
// A simple conversion exists to make this right.
val = val.Convert(to)
} else if to.Kind() == reflect.Ptr && val.Type().AssignableTo(to.Elem()) {
// If the target is a pointer, turn the target into a pointer. If it's not addressable, make a copy.
if val.CanAddr() {
val = val.Addr()
} else {
slot := reflect.New(val.Type().Elem())
copy := reflect.ValueOf(val.Interface())
contract.Assert(copy.CanAddr())
slot.Set(copy)
val = slot
}
} else if val.Kind() == reflect.Interface {
// It could be that the source is an interface{} with the right element type (or the right element type
// through a series of successive conversions); go ahead and give it a try.
val = val.Elem()
} else if val.Type().Kind() == reflect.Slice && to.Kind() == reflect.Slice {
// If a slice, everything's ok so long as the elements are compatible.
arr := reflect.New(to).Elem()
for i := 0; i < val.Len(); i++ {
elem := val.Index(i)
if !elem.Type().AssignableTo(to.Elem()) {
ekey := fmt.Sprintf("%v[%v]", key, i)
var err FieldError
if elem, err = md.adjustValueForAssignment(elem, to.Elem(), ty, ekey); err != nil {
return val, err
}
if !elem.Type().AssignableTo(to.Elem()) {
return val, NewWrongTypeError(ty, ekey, to.Elem(), elem.Type())
}
}
arr = reflect.Append(arr, elem)
}
val = arr
} else if val.Type().Kind() == reflect.Map && to.Kind() == reflect.Map {
// Similarly, if a map, everything's ok so long as elements and keys are compatible.
m := reflect.MakeMap(to)
for _, k := range val.MapKeys() {
entry := val.MapIndex(k)
if !k.Type().AssignableTo(to.Key()) {
kkey := fmt.Sprintf("%v[%v] key", key, k.Interface())
var err FieldError
if k, err = md.adjustValueForAssignment(k, to.Key(), ty, kkey); err != nil {
return val, err
}
if !k.Type().AssignableTo(to.Key()) {
return val, NewWrongTypeError(ty, kkey, to.Key(), k.Type())
}
}
if !entry.Type().AssignableTo(to.Elem()) {
ekey := fmt.Sprintf("%v[%v] value", key, k.Interface())
var err FieldError
if entry, err = md.adjustValueForAssignment(entry, to.Elem(), ty, ekey); err != nil {
return val, err
}
if !entry.Type().AssignableTo(to.Elem()) {
return val, NewWrongTypeError(ty, ekey, to.Elem(), entry.Type())
}
}
m.SetMapIndex(k, entry)
}
val = m
} else if val.Type() == reflect.TypeOf(emptyObject) {
// The value is an object and needs to be decoded into a value.
obj := val.Interface().(map[string]interface{})
if decode, has := md.opts.CustomDecoders[to]; has {
// A custom decoder exists; use it to unmarshal the type.
target, err := decode(md, obj)
if err != nil {
return val, NewTypeFieldError(ty, key, err)
}
val = reflect.ValueOf(target)
} else if to.Kind() == reflect.Struct || (to.Kind() == reflect.Ptr && to.Elem().Kind() == reflect.Struct) {
// If the target is a struct, we can use the built-in decoding logic.
var target interface{}
if to.Kind() == reflect.Ptr {
target = reflect.New(to.Elem()).Interface()
} else {
target = reflect.New(to).Interface()
}
if err := md.Decode(obj, target); err != nil {
return val, NewTypeFieldError(ty, key, err)
}
val = reflect.ValueOf(target).Elem()
} else {
return val, NewTypeFieldError(ty, key,
errors.Errorf(
"Cannot decode Object{} to type %v; it isn't a struct, and no custom decoder exists", to))
}
} else if val.Type().Kind() == reflect.String {
// If the source is a string, see if the target implements encoding.TextUnmarshaler.
target := reflect.New(to)
if target.Type().Implements(textUnmarshalerType) {
um := target.Interface().(encoding.TextUnmarshaler)
if err := um.UnmarshalText([]byte(val.String())); err != nil {
return val, NewTypeFieldError(ty, key, err)
}
val = target.Elem()
} else {
break
}
} else {
break
}
}
return val, nil
}