github.com/linchen2chris/hugo@v0.0.0-20230307053224-cec209389705/tpl/collections/symdiff.go (about)

     1  // Copyright 2018 The Hugo Authors. All rights reserved.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  // http://www.apache.org/licenses/LICENSE-2.0
     7  //
     8  // Unless required by applicable law or agreed to in writing, software
     9  // distributed under the License is distributed on an "AS IS" BASIS,
    10  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    11  // See the License for the specific language governing permissions and
    12  // limitations under the License.
    13  
    14  package collections
    15  
    16  import (
    17  	"fmt"
    18  	"reflect"
    19  )
    20  
    21  // SymDiff returns the symmetric difference of s1 and s2.
    22  // Arguments must be either a slice or an array of comparable types.
    23  func (ns *Namespace) SymDiff(s2, s1 any) (any, error) {
    24  	ids1, err := collectIdentities(s1)
    25  	if err != nil {
    26  		return nil, err
    27  	}
    28  	ids2, err := collectIdentities(s2)
    29  	if err != nil {
    30  		return nil, err
    31  	}
    32  
    33  	var slice reflect.Value
    34  	var sliceElemType reflect.Type
    35  
    36  	for i, s := range []any{s1, s2} {
    37  		v := reflect.ValueOf(s)
    38  
    39  		switch v.Kind() {
    40  		case reflect.Array, reflect.Slice:
    41  			if i == 0 {
    42  				sliceType := v.Type()
    43  				sliceElemType = sliceType.Elem()
    44  				slice = reflect.MakeSlice(sliceType, 0, 0)
    45  			}
    46  
    47  			for i := 0; i < v.Len(); i++ {
    48  				ev, _ := indirectInterface(v.Index(i))
    49  				key := normalize(ev)
    50  
    51  				// Append if the key is not in their intersection.
    52  				if ids1[key] != ids2[key] {
    53  					v, err := convertValue(ev, sliceElemType)
    54  					if err != nil {
    55  						return nil, fmt.Errorf("symdiff: failed to convert value: %w", err)
    56  					}
    57  					slice = reflect.Append(slice, v)
    58  				}
    59  			}
    60  		default:
    61  			return nil, fmt.Errorf("arguments to symdiff must be slices or arrays")
    62  		}
    63  	}
    64  
    65  	return slice.Interface(), nil
    66  }