Replace internal joined error with errors.Join

internal/errors/errors.go

@@ -0,0 +1,11 @@
+package errors
+
+import "errors"
+
+func New(text string) error {
+	return errors.New(text)
+}
+
+func As(err error, target interface{}) bool {
+	return errors.As(err, target)
+}

internal/errors/join.go

@@ -0,0 +1,9 @@
+//go:build go1.20
+
+package errors
+
+import "errors"
+
+func Join(errs ...error) error {
+	return errors.Join(errs...)
+}

internal/errors/join_go1_19.go

@@ -0,0 +1,61 @@
+//go:build !go1.20
+
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package errors
+
+// Join returns an error that wraps the given errors.
+// Any nil error values are discarded.
+// Join returns nil if every value in errs is nil.
+// The error formats as the concatenation of the strings obtained
+// by calling the Error method of each element of errs, with a newline
+// between each string.
+//
+// A non-nil error returned by Join implements the Unwrap() []error method.
+func Join(errs ...error) error {
+	n := 0
+	for _, err := range errs {
+		if err != nil {
+			n++
+		}
+	}
+	if n == 0 {
+		return nil
+	}
+	e := &joinError{
+		errs: make([]error, 0, n),
+	}
+	for _, err := range errs {
+		if err != nil {
+			e.errs = append(e.errs, err)
+		}
+	}
+	return e
+}
+
+type joinError struct {
+	errs []error
+}
+
+func (e *joinError) Error() string {
+	// Since Join returns nil if every value in errs is nil,
+	// e.errs cannot be empty.
+	if len(e.errs) == 1 {
+		return e.errs[0].Error()
+	}
+
+	b := []byte(e.errs[0].Error())
+	for _, err := range e.errs[1:] {
+		b = append(b, '\n')
+		b = append(b, err.Error()...)
+	}
+	// At this point, b has at least one byte '\n'.
+	// return unsafe.String(&b[0], len(b))
+	return string(b)
+}
+
+func (e *joinError) Unwrap() []error {
+	return e.errs
+}

mapstructure.go

@@ -160,12 +160,13 @@ package mapstructure
 
 import (
 	"encoding/json"
-	"errors"
 	"fmt"
 	"reflect"
 	"sort"
 	"strconv"
 	"strings"
+
+	"github.com/go-viper/mapstructure/v2/internal/errors"
 )
 
 // DecodeHookFunc is the callback function that can be used for
@@ -414,7 +415,15 @@ func NewDecoder(config *DecoderConfig) (*Decoder, error) {
 // Decode decodes the given raw interface to the target pointer specified
 // by the configuration.
 func (d *Decoder) Decode(input interface{}) error {
-	return d.decode("", input, reflect.ValueOf(d.config.Result).Elem())
+	err := d.decode("", input, reflect.ValueOf(d.config.Result).Elem())
+
+	// Retain some of the original behavior when multiple errors ocurr
+	var joinedErr interface{ Unwrap() []error }
+	if errors.As(err, &joinedErr) {
+		return fmt.Errorf("decoding failed due to the following error(s):\n\n%w", err)
+	}
+
+	return err
 }
 
 // Decodes an unknown data type into a specific reflection value.
@@ -881,7 +890,7 @@ func (d *Decoder) decodeMapFromMap(name string, dataVal reflect.Value, val refle
 	valElemType := valType.Elem()
 
 	// Accumulate errors
-	errors := make([]string, 0)
+	var errs []error
 
 	// If the input data is empty, then we just match what the input data is.
 	if dataVal.Len() == 0 {
@@ -903,15 +912,15 @@ func (d *Decoder) decodeMapFromMap(name string, dataVal reflect.Value, val refle
 		// First decode the key into the proper type
 		currentKey := reflect.Indirect(reflect.New(valKeyType))
 		if err := d.decode(fieldName, k.Interface(), currentKey); err != nil {
-			errors = appendErrors(errors, err)
+			errs = append(errs, err)
 			continue
 		}
 
 		// Next decode the data into the proper type
 		v := dataVal.MapIndex(k).Interface()
 		currentVal := reflect.Indirect(reflect.New(valElemType))
 		if err := d.decode(fieldName, v, currentVal); err != nil {
-			errors = appendErrors(errors, err)
+			errs = append(errs, err)
 			continue
 		}
 
@@ -921,12 +930,7 @@ func (d *Decoder) decodeMapFromMap(name string, dataVal reflect.Value, val refle
 	// Set the built up map to the value
 	val.Set(valMap)
 
-	// If we had errors, return those
-	if len(errors) > 0 {
-		return &joinedError{errors}
-	}
-
-	return nil
+	return errors.Join(errs...)
 }
 
 func (d *Decoder) decodeMapFromStruct(name string, dataVal reflect.Value, val reflect.Value, valMap reflect.Value) error {
@@ -1164,7 +1168,7 @@ func (d *Decoder) decodeSlice(name string, data interface{}, val reflect.Value)
 	}
 
 	// Accumulate any errors
-	errors := make([]string, 0)
+	var errs []error
 
 	for i := 0; i < dataVal.Len(); i++ {
 		currentData := dataVal.Index(i).Interface()
@@ -1175,19 +1179,14 @@ func (d *Decoder) decodeSlice(name string, data interface{}, val reflect.Value)
 
 		fieldName := name + "[" + strconv.Itoa(i) + "]"
 		if err := d.decode(fieldName, currentData, currentField); err != nil {
-			errors = appendErrors(errors, err)
+			errs = append(errs, err)
 		}
 	}
 
 	// Finally, set the value to the slice we built up
 	val.Set(valSlice)
 
-	// If there were errors, we return those
-	if len(errors) > 0 {
-		return &joinedError{errors}
-	}
-
-	return nil
+	return errors.Join(errs...)
 }
 
 func (d *Decoder) decodeArray(name string, data interface{}, val reflect.Value) error {
@@ -1233,27 +1232,22 @@ func (d *Decoder) decodeArray(name string, data interface{}, val reflect.Value)
 	}
 
 	// Accumulate any errors
-	errors := make([]string, 0)
+	var errs []error
 
 	for i := 0; i < dataVal.Len(); i++ {
 		currentData := dataVal.Index(i).Interface()
 		currentField := valArray.Index(i)
 
 		fieldName := name + "[" + strconv.Itoa(i) + "]"
 		if err := d.decode(fieldName, currentData, currentField); err != nil {
-			errors = appendErrors(errors, err)
+			errs = append(errs, err)
 		}
 	}
 
 	// Finally, set the value to the array we built up
 	val.Set(valArray)
 
-	// If there were errors, we return those
-	if len(errors) > 0 {
-		return &joinedError{errors}
-	}
-
-	return nil
+	return errors.Join(errs...)
 }
 
 func (d *Decoder) decodeStruct(name string, data interface{}, val reflect.Value) error {
@@ -1315,7 +1309,8 @@ func (d *Decoder) decodeStructFromMap(name string, dataVal, val reflect.Value) e
 	}
 
 	targetValKeysUnused := make(map[interface{}]struct{})
-	errors := make([]string, 0)
+
+	var errs []error
 
 	// This slice will keep track of all the structs we'll be decoding.
 	// There can be more than one struct if there are embedded structs
@@ -1369,8 +1364,7 @@ func (d *Decoder) decodeStructFromMap(name string, dataVal, val reflect.Value) e
 
 			if squash {
 				if fieldVal.Kind() != reflect.Struct {
-					errors = appendErrors(errors,
-						fmt.Errorf("%s: unsupported type for squash: %s", fieldType.Name, fieldVal.Kind()))
+					errs = append(errs, fmt.Errorf("%s: unsupported type for squash: %s", fieldType.Name, fieldVal.Kind()))
 				} else {
 					structs = append(structs, fieldVal)
 				}
@@ -1449,7 +1443,7 @@ func (d *Decoder) decodeStructFromMap(name string, dataVal, val reflect.Value) e
 		}
 
 		if err := d.decode(fieldName, rawMapVal.Interface(), fieldValue); err != nil {
-			errors = appendErrors(errors, err)
+			errs = append(errs, err)
 		}
 	}
 
@@ -1464,7 +1458,7 @@ func (d *Decoder) decodeStructFromMap(name string, dataVal, val reflect.Value) e
 
 		// Decode it as-if we were just decoding this map onto our map.
 		if err := d.decodeMap(name, remain, remainField.val); err != nil {
-			errors = appendErrors(errors, err)
+			errs = append(errs, err)
 		}
 
 		// Set the map to nil so we have none so that the next check will
@@ -1480,7 +1474,7 @@ func (d *Decoder) decodeStructFromMap(name string, dataVal, val reflect.Value) e
 		sort.Strings(keys)
 
 		err := fmt.Errorf("'%s' has invalid keys: %s", name, strings.Join(keys, ", "))
-		errors = appendErrors(errors, err)
+		errs = append(errs, err)
 	}
 
 	if d.config.ErrorUnset && len(targetValKeysUnused) > 0 {
@@ -1491,11 +1485,11 @@ func (d *Decoder) decodeStructFromMap(name string, dataVal, val reflect.Value) e
 		sort.Strings(keys)
 
 		err := fmt.Errorf("'%s' has unset fields: %s", name, strings.Join(keys, ", "))
-		errors = appendErrors(errors, err)
+		errs = append(errs, err)
 	}
 
-	if len(errors) > 0 {
-		return &joinedError{errors}
+	if err := errors.Join(errs...); err != nil {
+		return err
 	}
 
 	// Add the unused keys to the list of unused keys if we're tracking metadata

mapstructure_examples_test.go

@@ -63,13 +63,13 @@ func ExampleDecode_errors() {
 
 	fmt.Println(err.Error())
 	// Output:
-	// 5 error(s) decoding:
+	// decoding failed due to the following error(s):
 	//
-	// * 'Age' expected type 'int', got unconvertible type 'string', value: 'bad value'
-	// * 'Emails[0]' expected type 'string', got unconvertible type 'int', value: '1'
-	// * 'Emails[1]' expected type 'string', got unconvertible type 'int', value: '2'
-	// * 'Emails[2]' expected type 'string', got unconvertible type 'int', value: '3'
-	// * 'Name' expected type 'string', got unconvertible type 'int', value: '123'
+	// 'Name' expected type 'string', got unconvertible type 'int', value: '123'
+	// 'Age' expected type 'int', got unconvertible type 'string', value: 'bad value'
+	// 'Emails[0]' expected type 'string', got unconvertible type 'int', value: '1'
+	// 'Emails[1]' expected type 'string', got unconvertible type 'int', value: '2'
+	// 'Emails[2]' expected type 'string', got unconvertible type 'int', value: '3'
 }
 
 func ExampleDecode_metadata() {