github.com/justincormack/cli@v0.0.0-20201215022714-831ebeae9675/cli/command/formatter/reflect.go (about)

     1  package formatter
     2  
     3  import (
     4  	"encoding/json"
     5  	"reflect"
     6  	"unicode"
     7  
     8  	"github.com/pkg/errors"
     9  )
    10  
    11  // MarshalJSON marshals x into json
    12  // It differs a bit from encoding/json MarshalJSON function for formatter
    13  func MarshalJSON(x interface{}) ([]byte, error) {
    14  	m, err := marshalMap(x)
    15  	if err != nil {
    16  		return nil, err
    17  	}
    18  	return json.Marshal(m)
    19  }
    20  
    21  // marshalMap marshals x to map[string]interface{}
    22  func marshalMap(x interface{}) (map[string]interface{}, error) {
    23  	val := reflect.ValueOf(x)
    24  	if val.Kind() != reflect.Ptr {
    25  		return nil, errors.Errorf("expected a pointer to a struct, got %v", val.Kind())
    26  	}
    27  	if val.IsNil() {
    28  		return nil, errors.Errorf("expected a pointer to a struct, got nil pointer")
    29  	}
    30  	valElem := val.Elem()
    31  	if valElem.Kind() != reflect.Struct {
    32  		return nil, errors.Errorf("expected a pointer to a struct, got a pointer to %v", valElem.Kind())
    33  	}
    34  	typ := val.Type()
    35  	m := make(map[string]interface{})
    36  	for i := 0; i < val.NumMethod(); i++ {
    37  		k, v, err := marshalForMethod(typ.Method(i), val.Method(i))
    38  		if err != nil {
    39  			return nil, err
    40  		}
    41  		if k != "" {
    42  			m[k] = v
    43  		}
    44  	}
    45  	return m, nil
    46  }
    47  
    48  var unmarshallableNames = map[string]struct{}{"FullHeader": {}}
    49  
    50  // marshalForMethod returns the map key and the map value for marshalling the method.
    51  // It returns ("", nil, nil) for valid but non-marshallable parameter. (e.g. "unexportedFunc()")
    52  func marshalForMethod(typ reflect.Method, val reflect.Value) (string, interface{}, error) {
    53  	if val.Kind() != reflect.Func {
    54  		return "", nil, errors.Errorf("expected func, got %v", val.Kind())
    55  	}
    56  	name, numIn, numOut := typ.Name, val.Type().NumIn(), val.Type().NumOut()
    57  	_, blackListed := unmarshallableNames[name]
    58  	// FIXME: In text/template, (numOut == 2) is marshallable,
    59  	//        if the type of the second param is error.
    60  	marshallable := unicode.IsUpper(rune(name[0])) && !blackListed &&
    61  		numIn == 0 && numOut == 1
    62  	if !marshallable {
    63  		return "", nil, nil
    64  	}
    65  	result := val.Call(make([]reflect.Value, numIn))
    66  	intf := result[0].Interface()
    67  	return name, intf, nil
    68  }