DockerCLI/cli/command/formatter/reflect.go

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package formatter
import (
"encoding/json"
"reflect"
"unicode"
"github.com/pkg/errors"
)
// MarshalJSON marshals x into json
// It differs a bit from encoding/json MarshalJSON function for formatter
func MarshalJSON(x interface{}) ([]byte, error) {
m, err := marshalMap(x)
if err != nil {
return nil, err
}
return json.Marshal(m)
}
// marshalMap marshals x to map[string]interface{}
func marshalMap(x interface{}) (map[string]interface{}, error) {
val := reflect.ValueOf(x)
if val.Kind() != reflect.Ptr {
return nil, errors.Errorf("expected a pointer to a struct, got %v", val.Kind())
}
if val.IsNil() {
return nil, errors.Errorf("expected a pointer to a struct, got nil pointer")
}
valElem := val.Elem()
if valElem.Kind() != reflect.Struct {
return nil, errors.Errorf("expected a pointer to a struct, got a pointer to %v", valElem.Kind())
}
typ := val.Type()
m := make(map[string]interface{})
for i := 0; i < val.NumMethod(); i++ {
k, v, err := marshalForMethod(typ.Method(i), val.Method(i))
if err != nil {
return nil, err
}
if k != "" {
m[k] = v
}
}
return m, nil
}
var unmarshallableNames = map[string]struct{}{"FullHeader": {}}
// marshalForMethod returns the map key and the map value for marshalling the method.
// It returns ("", nil, nil) for valid but non-marshallable parameter. (e.g. "unexportedFunc()")
func marshalForMethod(typ reflect.Method, val reflect.Value) (string, interface{}, error) {
if val.Kind() != reflect.Func {
return "", nil, errors.Errorf("expected func, got %v", val.Kind())
}
name, numIn, numOut := typ.Name, val.Type().NumIn(), val.Type().NumOut()
_, blackListed := unmarshallableNames[name]
// FIXME: In text/template, (numOut == 2) is marshallable,
// if the type of the second param is error.
marshallable := unicode.IsUpper(rune(name[0])) && !blackListed &&
numIn == 0 && numOut == 1
if !marshallable {
return "", nil, nil
}
result := val.Call(make([]reflect.Value, numIn))
intf := result[0].Interface()
return name, intf, nil
}