jsonpatch - walk.go

     1  package jsonpatch
     2  
     3  import (
     4  	"errors"
     5  	"iter"
     6  	"reflect"
     7  	"strconv"
     8  	"strings"
     9  )
    10  
    11  func walkType(t any, path iter.Seq[string], allowArray bool) (any, error) {
    12  	v := reflect.ValueOf(t)
    13  
    14  	for p := range path {
    15  		if v.Kind() == reflect.Pointer {
    16  			v = v.Elem()
    17  		}
    18  
    19  		var (
    20  			found   reflect.Value
    21  			index   uint64
    22  			isIndex bool
    23  		)
    24  
    25  		if allowArray {
    26  			var err error
    27  
    28  			index, err = strconv.ParseUint(p, 10, 64)
    29  			isIndex = err == nil && index >= 0
    30  		}
    31  
    32  		if isIndex && (v.Kind() == reflect.Array || v.Kind() == reflect.Slice) {
    33  			if uint64(v.Len()) <= index {
    34  				return nil, ErrInvalidPath
    35  			}
    36  
    37  			v = v.Index(int(index))
    38  
    39  			continue
    40  		} else if v.Kind() != reflect.Struct {
    41  			return nil, ErrInvalidValue
    42  		}
    43  
    44  		typeDepths := []reflect.Value{v}
    45  
    46  		for typeDepths != nil {
    47  			var anonStructs []reflect.Value
    48  
    49  			for _, typ := range typeDepths {
    50  				for field := range typ.Type().Fields() {
    51  					if field.Anonymous {
    52  						anonStructs = append(anonStructs, typ.FieldByName(field.Name))
    53  					} else if t, _, _ := strings.Cut(field.Tag.Get("json"), ","); t == p || t == "" && field.Name == p {
    54  						if found.IsValid() {
    55  							return nil, ErrInvalidValue
    56  						}
    57  
    58  						found = typ.FieldByName(field.Name)
    59  					}
    60  				}
    61  			}
    62  
    63  			if len(anonStructs) > 0 && !found.IsValid() {
    64  				typeDepths = anonStructs
    65  			} else {
    66  				typeDepths = nil
    67  			}
    68  		}
    69  
    70  		if !found.IsValid() {
    71  			return nil, ErrInvalidPath
    72  		}
    73  
    74  		v = found
    75  	}
    76  
    77  	if !v.CanSet() {
    78  		return nil, ErrInvalidValue
    79  	}
    80  
    81  	return v.Addr().Interface(), nil
    82  }
    83  
    84  var (
    85  	ErrInvalidValue = errors.New("invalid value")
    86  	ErrInvalidPath  = errors.New("invalid path")
    87  )
    88