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|
package gohcl
import (
"fmt"
"reflect"
"sort"
"strings"
"github.com/hashicorp/hcl/v2"
)
// ImpliedBodySchema produces a hcl.BodySchema derived from the type of the
// given value, which must be a struct value or a pointer to one. If an
// inappropriate value is passed, this function will panic.
//
// The second return argument indicates whether the given struct includes
// a "remain" field, and thus the returned schema is non-exhaustive.
//
// This uses the tags on the fields of the struct to discover how each
// field's value should be expressed within configuration. If an invalid
// mapping is attempted, this function will panic.
func ImpliedBodySchema(val interface{}) (schema *hcl.BodySchema, partial bool) {
ty := reflect.TypeOf(val)
if ty.Kind() == reflect.Ptr {
ty = ty.Elem()
}
if ty.Kind() != reflect.Struct {
panic(fmt.Sprintf("given value must be struct, not %T", val))
}
var attrSchemas []hcl.AttributeSchema
var blockSchemas []hcl.BlockHeaderSchema
tags := getFieldTags(ty)
attrNames := make([]string, 0, len(tags.Attributes))
for n := range tags.Attributes {
attrNames = append(attrNames, n)
}
sort.Strings(attrNames)
for _, n := range attrNames {
idx := tags.Attributes[n]
optional := tags.Optional[n]
field := ty.Field(idx)
var required bool
switch {
case field.Type.AssignableTo(exprType):
// If we're decoding to hcl.Expression then absense can be
// indicated via a null value, so we don't specify that
// the field is required during decoding.
required = false
case field.Type.Kind() != reflect.Ptr && !optional:
required = true
default:
required = false
}
attrSchemas = append(attrSchemas, hcl.AttributeSchema{
Name: n,
Required: required,
})
}
blockNames := make([]string, 0, len(tags.Blocks))
for n := range tags.Blocks {
blockNames = append(blockNames, n)
}
sort.Strings(blockNames)
for _, n := range blockNames {
idx := tags.Blocks[n]
field := ty.Field(idx)
fty := field.Type
if fty.Kind() == reflect.Slice {
fty = fty.Elem()
}
if fty.Kind() == reflect.Ptr {
fty = fty.Elem()
}
if fty.Kind() != reflect.Struct {
panic(fmt.Sprintf(
"hcl 'block' tag kind cannot be applied to %s field %s: struct required", field.Type.String(), field.Name,
))
}
ftags := getFieldTags(fty)
var labelNames []string
if len(ftags.Labels) > 0 {
labelNames = make([]string, len(ftags.Labels))
for i, l := range ftags.Labels {
labelNames[i] = l.Name
}
}
blockSchemas = append(blockSchemas, hcl.BlockHeaderSchema{
Type: n,
LabelNames: labelNames,
})
}
partial = tags.Remain != nil
schema = &hcl.BodySchema{
Attributes: attrSchemas,
Blocks: blockSchemas,
}
return schema, partial
}
type fieldTags struct {
Attributes map[string]int
Blocks map[string]int
Labels []labelField
Remain *int
Body *int
Optional map[string]bool
}
type labelField struct {
FieldIndex int
Name string
}
func getFieldTags(ty reflect.Type) *fieldTags {
ret := &fieldTags{
Attributes: map[string]int{},
Blocks: map[string]int{},
Optional: map[string]bool{},
}
ct := ty.NumField()
for i := 0; i < ct; i++ {
field := ty.Field(i)
tag := field.Tag.Get("hcl")
if tag == "" {
continue
}
comma := strings.Index(tag, ",")
var name, kind string
if comma != -1 {
name = tag[:comma]
kind = tag[comma+1:]
} else {
name = tag
kind = "attr"
}
switch kind {
case "attr":
ret.Attributes[name] = i
case "block":
ret.Blocks[name] = i
case "label":
ret.Labels = append(ret.Labels, labelField{
FieldIndex: i,
Name: name,
})
case "remain":
if ret.Remain != nil {
panic("only one 'remain' tag is permitted")
}
idx := i // copy, because this loop will continue assigning to i
ret.Remain = &idx
case "body":
if ret.Body != nil {
panic("only one 'body' tag is permitted")
}
idx := i // copy, because this loop will continue assigning to i
ret.Body = &idx
case "optional":
ret.Attributes[name] = i
ret.Optional[name] = true
default:
panic(fmt.Sprintf("invalid hcl field tag kind %q on %s %q", kind, field.Type.String(), field.Name))
}
}
return ret
}
|
