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reflect.go
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reflect.go
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package tmpl
import (
"fmt"
"reflect"
)
type FieldNode struct {
Value reflect.Value
StructField reflect.StructField
Parent *FieldNode
Children []*FieldNode
}
func (node *FieldNode) IsKind(kind reflect.Kind) (reflect.Kind, bool) {
if node.StructField.Type.Kind() == reflect.Interface && node.Value.Kind() != kind {
return node.Value.Kind(), false
} else if node.StructField.Type.Kind() != kind {
return node.StructField.Type.Kind(), false
} else {
return kind, true
}
}
func (node *FieldNode) GetKind() reflect.Kind {
if node.StructField.Type.Kind() == reflect.Interface {
return node.Value.Kind()
} else {
return node.StructField.Type.Kind()
}
}
func (node *FieldNode) FindPath(path []string) *FieldNode {
if len(path) == 0 {
return node
}
for _, child := range node.Children {
if child.StructField.Name == path[0] {
return child.FindPath(path[1:])
}
}
return nil
}
// createFieldTree can be used to create a tree structure of the fields in a struct
func createFieldTree(structOrPtr interface{}) (root *FieldNode, err error) {
root = &FieldNode{
Value: reflect.ValueOf(structOrPtr),
StructField: reflect.StructField{
Name: fmt.Sprintf("%T", structOrPtr),
},
Parent: nil,
Children: make([]*FieldNode, 0),
}
if root.Value.Kind() == reflect.Ptr {
// detect all methods on this pointer
val := root.Value
for i := 0; i < val.NumMethod(); i++ {
methodVal := val.Method(i)
methodTyp := val.Type().Method(i)
node := &FieldNode{
Value: methodVal,
StructField: reflect.StructField{
Name: methodTyp.Name,
Type: methodTyp.Type,
},
Parent: root,
Children: make([]*FieldNode, 0),
}
root.Children = append(root.Children, node)
// for each of the values returned by this method,
// create a field tree and append it as a child
for j := 0; j < methodVal.Type().NumOut(); j++ {
retTyp := methodVal.Type().Out(j)
var retVal reflect.Value
if retTyp.Kind() == reflect.Ptr {
retVal = reflect.New(retTyp.Elem())
} else {
retVal = reflect.New(retTyp).Elem()
}
retTypSwitch:
switch retTyp.Kind() {
case reflect.Ptr:
fallthrough
case reflect.Struct:
// check for circular dependencies, if found, append the parent node
// as a child of the returned tree instead of recurring again
for temp := node.Parent; temp != nil; temp = temp.Parent {
if temp.Value.Type() == retTyp {
node.Children = append(node.Children, temp.Children...)
break retTypSwitch
}
}
tree, err := createFieldTree(retVal.Interface())
if err != nil {
return root, err
}
// the children of the returned tree should be children of this node
node.Children = append(node.Children, tree.Children...)
}
}
}
// convert this pointer to a value
root.Value = val.Elem()
}
if root.Value.Kind() != reflect.Struct {
return
}
val := root.Value
for i := 0; i < val.NumField(); i++ {
iface := zeroValueInterfaceFromField(val.Field(i))
if iface != nil {
node, err := createFieldTree(iface)
if err != nil {
return nil, err
}
node.StructField = val.Type().Field(i)
node.Parent = root
root.Children = append(root.Children, node)
//support embedded struct fields
if node.StructField.Anonymous {
for _, child := range node.Children {
child.Parent = root
root.Children = append(root.Children, child)
}
}
} else if val.Field(i).Kind() == reflect.Struct {
node := &FieldNode{
Value: val.Field(i),
StructField: val.Type().Field(i),
Parent: root,
Children: make([]*FieldNode, 0),
}
root.Children = append(root.Children, node)
} else {
node := &FieldNode{
Value: val.Field(i),
StructField: reflect.StructField{
Name: val.Type().Field(i).Name,
Type: val.Type().Field(i).Type,
},
Parent: root,
Children: make([]*FieldNode, 0),
}
root.Children = append(root.Children, node)
}
}
return root, nil
}
func recurseFieldsImplementing[T interface{}](structOrPtr interface{}, fn func(val T, field reflect.StructField) error) error {
val := reflect.ValueOf(structOrPtr)
if val.Kind() == reflect.Ptr {
val = val.Elem()
}
iface := zeroValueInterfaceFromField(val)
if t, ok := iface.(T); ok {
err := fn(t, reflect.StructField{
Name: fmt.Sprintf("%T", structOrPtr),
})
if err != nil {
return err
}
}
for i := 0; i < val.NumField(); i++ {
field := val.Field(i)
if field.Kind() != reflect.Ptr &&
field.Kind() != reflect.Slice &&
field.Kind() != reflect.Struct {
continue
}
iface := zeroValueInterfaceFromField(field)
if t, ok := iface.(T); ok {
err := fn(t, val.Type().Field(i))
if err != nil {
return err
}
err = recurseFieldsImplementing[T](t, fn)
if err != nil {
return err
}
}
}
return nil
}
// zeroValueInterfaceFromField converts a reflected field to a zero'd version of itself as an interface type.
// this makes it easier to perform type assertions on reflected struct fields
func zeroValueInterfaceFromField(field reflect.Value) interface{} {
switch field.Kind() {
case reflect.Struct:
if field.Type().Kind() == reflect.Ptr {
return reflect.New(field.Type().Elem()).Interface()
} else {
return reflect.New(field.Type()).Interface()
}
case reflect.Ptr:
fallthrough
case reflect.Slice:
if field.Type().Elem().Kind() == reflect.Ptr {
return reflect.New(field.Type().Elem().Elem()).Interface()
} else {
return reflect.New(field.Type().Elem()).Interface()
}
}
return nil
}