From 0ea879d727db0dcf3367424b05564787446a9de9 Mon Sep 17 00:00:00 2001
From: Colin Leroy-Mira <colin.leroy-mira@unabiz.com>
Date: Mon, 23 Jun 2025 11:26:17 +0200
Subject: [PATCH] Fix warning on nil tag

Signed-off-by: Colin Leroy-Mira <colin.leroy-mira@unabiz.com>
---
 lib/fluent/plugin/prometheus/placeholder_expander.rb | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/lib/fluent/plugin/prometheus/placeholder_expander.rb b/lib/fluent/plugin/prometheus/placeholder_expander.rb
index 53f5d28..79f205a 100644
--- a/lib/fluent/plugin/prometheus/placeholder_expander.rb
+++ b/lib/fluent/plugin/prometheus/placeholder_expander.rb
@@ -39,6 +39,8 @@ def build(placeholder_values)
         private
 
         def build_tag(tag)
+          return [] if tag.nil?
+
           tags = tag.split('.')
 
           placeholders = { '${tag}' => tag }