From bdf72caffdf304888e3875b823080c5a86887211 Mon Sep 17 00:00:00 2001
From: Florian Zouhar <mail@zouhar.io>
Date: Tue, 6 Aug 2024 20:05:00 -0700
Subject: [PATCH] default value implementation * default value config * set
 default value in context source if metadata empty

fixes #34412
---
 extension/headerssetterextension/config.go               | 9 +++++----
 extension/headerssetterextension/extension.go            | 3 ++-
 .../headerssetterextension/internal/source/context.go    | 5 +++--
 3 files changed, 10 insertions(+), 7 deletions(-)

diff --git a/extension/headerssetterextension/config.go b/extension/headerssetterextension/config.go
index 5b73e9912f8f..6eade8416b4d 100644
--- a/extension/headerssetterextension/config.go
+++ b/extension/headerssetterextension/config.go
@@ -19,10 +19,11 @@ type Config struct {
 }
 
 type HeaderConfig struct {
-	Action      ActionValue `mapstructure:"action"`
-	Key         *string     `mapstructure:"key"`
-	Value       *string     `mapstructure:"value"`
-	FromContext *string     `mapstructure:"from_context"`
+	Action       ActionValue `mapstructure:"action"`
+	Key          *string     `mapstructure:"key"`
+	Value        *string     `mapstructure:"value"`
+	FromContext  *string     `mapstructure:"from_context"`
+	DefaultValue *string     `mapstructure:"default_value"`
 }
 
 // ActionValue is the enum to capture the four types of actions to perform on a header
diff --git a/extension/headerssetterextension/extension.go b/extension/headerssetterextension/extension.go
index ae2c0afbb752..5bdf447c0ed4 100644
--- a/extension/headerssetterextension/extension.go
+++ b/extension/headerssetterextension/extension.go
@@ -36,7 +36,8 @@ func newHeadersSetterExtension(cfg *Config, logger *zap.Logger) (auth.Client, er
 			}
 		} else if header.FromContext != nil {
 			s = &source.ContextSource{
-				Key: *header.FromContext,
+				Key:          *header.FromContext,
+				DefaultValue: *header.DefaultValue,
 			}
 		}
 
diff --git a/extension/headerssetterextension/internal/source/context.go b/extension/headerssetterextension/internal/source/context.go
index 7cd40b7dadb2..20b15fb2f7eb 100644
--- a/extension/headerssetterextension/internal/source/context.go
+++ b/extension/headerssetterextension/internal/source/context.go
@@ -13,7 +13,8 @@ import (
 var _ Source = (*ContextSource)(nil)
 
 type ContextSource struct {
-	Key string
+	Key          string
+	DefaultValue string
 }
 
 func (ts *ContextSource) Get(ctx context.Context) (string, error) {
@@ -21,7 +22,7 @@ func (ts *ContextSource) Get(ctx context.Context) (string, error) {
 	ss := cl.Metadata.Get(ts.Key)
 
 	if len(ss) == 0 {
-		return "", nil
+		return ts.DefaultValue, nil
 	}
 
 	if len(ss) > 1 {