From d77e7a7fbf29fc1658774bdea46676c997def41c Mon Sep 17 00:00:00 2001
From: Mark Sagi-Kazar <mark.sagikazar@gmail.com>
Date: Fri, 4 Jan 2019 23:17:38 +0100
Subject: [PATCH] Add string replacer interface

---
 README.md |  6 +++---
 viper.go  | 14 ++++++++++----
 2 files changed, 13 insertions(+), 7 deletions(-)

diff --git a/README.md b/README.md
index 0208eac..63b7f3c 100644
--- a/README.md
+++ b/README.md
@@ -185,8 +185,8 @@ with ENV:
  * `AutomaticEnv()`
  * `BindEnv(string...) : error`
  * `SetEnvPrefix(string)`
- * `SetEnvKeyReplacer(string...) *strings.Replacer`
-  * `AllowEmptyEnvVar(bool)`
+ * `SetEnvKeyReplacer(StringReplacer)`
+ * `AllowEmptyEnvVar(bool)`
 
 _When working with ENV variables, it’s important to recognize that Viper
 treats ENV variables as case sensitive._
@@ -213,7 +213,7 @@ time a `viper.Get` request is made. It will apply the following rules. It will
 check for a environment variable with a name matching the key uppercased and
 prefixed with the `EnvPrefix` if set.
 
-`SetEnvKeyReplacer` allows you to use a `strings.Replacer` object to rewrite Env
+`SetEnvKeyReplacer` allows you to use a `StringReplacer` object to rewrite Env
 keys to an extent. This is useful if you want to use `-` or something in your
 `Get()` calls, but want your environmental variables to use `_` delimiters. An
 example of using it can be found in `viper_test.go`.
diff --git a/viper.go b/viper.go
index cee37b2..caa9609 100644
--- a/viper.go
+++ b/viper.go
@@ -131,6 +131,12 @@ func DecodeHook(hook mapstructure.DecodeHookFunc) DecoderConfigOption {
 	}
 }
 
+// StringReplacer applies a set of replacements to a string.
+type StringReplacer interface {
+	// Replace returns a copy of s with all replacements performed.
+	Replace(s string) string
+}
+
 // Viper is a prioritized configuration registry. It
 // maintains a set of configuration sources, fetches
 // values to populate those, and provides them according
@@ -186,7 +192,7 @@ type Viper struct {
 	envPrefix  string
 
 	automaticEnvApplied bool
-	envKeyReplacer      *strings.Replacer
+	envKeyReplacer      StringReplacer
 	allowEmptyEnv       bool
 
 	config         map[string]interface{}
@@ -1095,11 +1101,11 @@ func (v *Viper) AutomaticEnv() {
 	v.automaticEnvApplied = true
 }
 
-// SetEnvKeyReplacer sets the strings.Replacer on the viper object
+// SetEnvKeyReplacer sets the StringReplacer on the viper object
 // Useful for mapping an environmental variable to a key that does
 // not match it.
-func SetEnvKeyReplacer(r *strings.Replacer) { v.SetEnvKeyReplacer(r) }
-func (v *Viper) SetEnvKeyReplacer(r *strings.Replacer) {
+func SetEnvKeyReplacer(r StringReplacer) { v.SetEnvKeyReplacer(r) }
+func (v *Viper) SetEnvKeyReplacer(r StringReplacer) {
 	v.envKeyReplacer = r
 }