From 8c1b96127969350e2a6acb8e677d3cca50de6e12 Mon Sep 17 00:00:00 2001
From: Yauhen Lazurkin <foryauhen@gmail.com>
Date: Fri, 23 Sep 2016 23:32:50 +0300
Subject: [PATCH] Issue-105 Add support of time.Duration in v.UnmarshalExact

---
 viper.go | 32 +++++++++++++-------------------
 1 file changed, 13 insertions(+), 19 deletions(-)

diff --git a/viper.go b/viper.go
index 1b381dd..4f15709 100644
--- a/viper.go
+++ b/viper.go
@@ -611,19 +611,7 @@ func (v *Viper) UnmarshalKey(key string, rawVal interface{}) error {
 // on the fields of the structure are properly set.
 func Unmarshal(rawVal interface{}) error { return v.Unmarshal(rawVal) }
 func (v *Viper) Unmarshal(rawVal interface{}) error {
-	config := &mapstructure.DecoderConfig{
-		Metadata:         nil,
-		Result:           rawVal,
-		WeaklyTypedInput: true,
-		DecodeHook:       mapstructure.StringToTimeDurationHookFunc(),
-	}
-
-	decoder, err := mapstructure.NewDecoder(config)
-	if err != nil {
-		return err
-	}
-
-	err = decoder.Decode(v.AllSettings())
+	err := decode(v.AllSettings(), defaultDecoderConfig(rawVal))
 
 	if err != nil {
 		return err
@@ -634,16 +622,19 @@ func (v *Viper) Unmarshal(rawVal interface{}) error {
 	return nil
 }
 
-// A wrapper around mapstructure.Decode that mimics the WeakDecode functionality
-// while erroring on non existing vals in the destination struct
-func weakDecodeExact(input, output interface{}) error {
-	config := &mapstructure.DecoderConfig{
-		ErrorUnused:      true,
+// defaultDecoderConfig returns default mapsstructure.DecoderConfig with suppot
+// of time.Duration values
+func defaultDecoderConfig(output interface{}) *mapstructure.DecoderConfig {
+	return &mapstructure.DecoderConfig{
 		Metadata:         nil,
 		Result:           output,
 		WeaklyTypedInput: true,
+		DecodeHook:       mapstructure.StringToTimeDurationHookFunc(),
 	}
+}
 
+// A wrapper around mapstructure.Decode that mimics the WeakDecode functionality
+func decode(input interface{}, config *mapstructure.DecoderConfig) error {
 	decoder, err := mapstructure.NewDecoder(config)
 	if err != nil {
 		return err
@@ -654,7 +645,10 @@ func weakDecodeExact(input, output interface{}) error {
 // Unmarshals the config into a Struct, erroring if a field is non-existant
 // in the destination struct
 func (v *Viper) UnmarshalExact(rawVal interface{}) error {
-	err := weakDecodeExact(v.AllSettings(), rawVal)
+	config := defaultDecoderConfig(rawVal)
+	config.ErrorUnused = true
+
+	err := decode(v.AllSettings(), config)
 
 	if err != nil {
 		return err