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package gohcl
import (
"fmt"
"reflect"
"sort"
"github.com/hashicorp/hcl2/hclwrite"
"github.com/zclconf/go-cty/cty/gocty"
)
// EncodeIntoBody replaces the contents of the given hclwrite Body with
// attributes and blocks derived from the given value, which must be a
// struct value or a pointer to a struct value with the struct tags defined
// in this package.
//
// This function can work only with fully-decoded data. It will ignore any
// fields tagged as "remain", any fields that decode attributes into either
// hcl.Attribute or hcl.Expression values, and any fields that decode blocks
// into hcl.Attributes values. This function does not have enough information
// to complete the decoding of these types.
//
// Any fields tagged as "label" are ignored by this function. Use EncodeAsBlock
// to produce a whole hclwrite.Block including block labels.
//
// As long as a suitable value is given to encode and the destination body
// is non-nil, this function will always complete. It will panic in case of
// any errors in the calling program, such as passing an inappropriate type
// or a nil body.
//
// The layout of the resulting HCL source is derived from the ordering of
// the struct fields, with blank lines around nested blocks of different types.
// Fields representing attributes should usually precede those representing
// blocks so that the attributes can group togather in the result. For more
// control, use the hclwrite API directly.
func EncodeIntoBody(val interface{}, dst *hclwrite.Body) {
rv := reflect.ValueOf(val)
ty := rv.Type()
if ty.Kind() == reflect.Ptr {
rv = rv.Elem()
ty = rv.Type()
}
if ty.Kind() != reflect.Struct {
panic(fmt.Sprintf("value is %s, not struct", ty.Kind()))
}
tags := getFieldTags(ty)
populateBody(rv, ty, tags, dst)
}
// EncodeAsBlock creates a new hclwrite.Block populated with the data from
// the given value, which must be a struct or pointer to struct with the
// struct tags defined in this package.
//
// If the given struct type has fields tagged with "label" tags then they
// will be used in order to annotate the created block with labels.
//
// This function has the same constraints as EncodeIntoBody and will panic
// if they are violated.
func EncodeAsBlock(val interface{}, blockType string) *hclwrite.Block {
rv := reflect.ValueOf(val)
ty := rv.Type()
if ty.Kind() == reflect.Ptr {
rv = rv.Elem()
ty = rv.Type()
}
if ty.Kind() != reflect.Struct {
panic(fmt.Sprintf("value is %s, not struct", ty.Kind()))
}
tags := getFieldTags(ty)
labels := make([]string, len(tags.Labels))
for i, lf := range tags.Labels {
lv := rv.Field(lf.FieldIndex)
// We just stringify whatever we find. It should always be a string
// but if not then we'll still do something reasonable.
labels[i] = fmt.Sprintf("%s", lv.Interface())
}
block := hclwrite.NewBlock(blockType, labels)
populateBody(rv, ty, tags, block.Body())
return block
}
func populateBody(rv reflect.Value, ty reflect.Type, tags *fieldTags, dst *hclwrite.Body) {
nameIdxs := make(map[string]int, len(tags.Attributes)+len(tags.Blocks))
namesOrder := make([]string, 0, len(tags.Attributes)+len(tags.Blocks))
for n, i := range tags.Attributes {
nameIdxs[n] = i
namesOrder = append(namesOrder, n)
}
for n, i := range tags.Blocks {
nameIdxs[n] = i
namesOrder = append(namesOrder, n)
}
sort.SliceStable(namesOrder, func(i, j int) bool {
ni, nj := namesOrder[i], namesOrder[j]
return nameIdxs[ni] < nameIdxs[nj]
})
dst.Clear()
prevWasBlock := false
for _, name := range namesOrder {
fieldIdx := nameIdxs[name]
field := ty.Field(fieldIdx)
fieldTy := field.Type
fieldVal := rv.Field(fieldIdx)
if fieldTy.Kind() == reflect.Ptr {
fieldTy = fieldTy.Elem()
fieldVal = fieldVal.Elem()
}
if _, isAttr := tags.Attributes[name]; isAttr {
if exprType.AssignableTo(fieldTy) || attrType.AssignableTo(fieldTy) {
continue // ignore undecoded fields
}
if !fieldVal.IsValid() {
continue // ignore (field value is nil pointer)
}
if fieldTy.Kind() == reflect.Ptr && fieldVal.IsNil() {
continue // ignore
}
if prevWasBlock {
dst.AppendNewline()
prevWasBlock = false
}
valTy, err := gocty.ImpliedType(fieldVal.Interface())
if err != nil {
panic(fmt.Sprintf("cannot encode %T as HCL expression: %s", fieldVal.Interface(), err))
}
val, err := gocty.ToCtyValue(fieldVal.Interface(), valTy)
if err != nil {
// This should never happen, since we should always be able
// to decode into the implied type.
panic(fmt.Sprintf("failed to encode %T as %#v: %s", fieldVal.Interface(), valTy, err))
}
dst.SetAttributeValue(name, val)
} else { // must be a block, then
elemTy := fieldTy
isSeq := false
if elemTy.Kind() == reflect.Slice || elemTy.Kind() == reflect.Array {
isSeq = true
elemTy = elemTy.Elem()
}
if bodyType.AssignableTo(elemTy) || attrsType.AssignableTo(elemTy) {
continue // ignore undecoded fields
}
prevWasBlock = false
if isSeq {
l := fieldVal.Len()
for i := 0; i < l; i++ {
elemVal := fieldVal.Index(i)
if !elemVal.IsValid() {
continue // ignore (elem value is nil pointer)
}
if elemTy.Kind() == reflect.Ptr && elemVal.IsNil() {
continue // ignore
}
block := EncodeAsBlock(elemVal.Interface(), name)
if !prevWasBlock {
dst.AppendNewline()
prevWasBlock = true
}
dst.AppendBlock(block)
}
} else {
if !fieldVal.IsValid() {
continue // ignore (field value is nil pointer)
}
if elemTy.Kind() == reflect.Ptr && fieldVal.IsNil() {
continue // ignore
}
block := EncodeAsBlock(fieldVal.Interface(), name)
if !prevWasBlock {
dst.AppendNewline()
prevWasBlock = true
}
dst.AppendBlock(block)
}
}
}
}
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