From 27c609531ddd7936b3e4ebfab42e6273cf28bd72 Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@home-assistant.io>
Date: Fri, 27 Mar 2026 13:34:36 -1000
Subject: [PATCH] [text_sensor] Use std::array in MapFilter

---
 esphome/components/text_sensor/__init__.py |  2 +-
 esphome/components/text_sensor/filter.cpp  | 14 ++++++--------
 esphome/components/text_sensor/filter.h    | 22 ++++++++++++++++++----
 3 files changed, 25 insertions(+), 13 deletions(-)

diff --git a/esphome/components/text_sensor/__init__.py b/esphome/components/text_sensor/__init__.py
index 97f394ecf7..8598fa06b2 100644
--- a/esphome/components/text_sensor/__init__.py
+++ b/esphome/components/text_sensor/__init__.py
@@ -136,7 +136,7 @@ async def map_filter_to_code(config, filter_id):
         )
         for conf in config
     ]
-    return cg.new_Pvariable(filter_id, mappings)
+    return cg.new_Pvariable(filter_id, cg.TemplateArguments(len(mappings)), mappings)
 
 
 validate_device_class = cv.one_of(*DEVICE_CLASSES, lower=True, space="_")
diff --git a/esphome/components/text_sensor/filter.cpp b/esphome/components/text_sensor/filter.cpp
index f7c6a695fb..bc044f3a73 100644
--- a/esphome/components/text_sensor/filter.cpp
+++ b/esphome/components/text_sensor/filter.cpp
@@ -93,17 +93,15 @@ bool SubstituteFilter::new_value(std::string &value) {
   return true;
 }
 
-// Map
-MapFilter::MapFilter(const std::initializer_list<Substitution> &mappings) : mappings_(mappings) {}
-
-bool MapFilter::new_value(std::string &value) {
-  for (const auto &mapping : this->mappings_) {
-    if (value == mapping.from) {
-      value.assign(mapping.to);
+// Map — non-template helper
+bool map_filter_apply(const Substitution *mappings, size_t count, std::string &value) {
+  for (size_t i = 0; i < count; i++) {
+    if (value == mappings[i].from) {
+      value.assign(mappings[i].to);
       return true;
     }
   }
-  return true;  // Pass through if no match
+  return true;
 }
 
 }  // namespace esphome::text_sensor
diff --git a/esphome/components/text_sensor/filter.h b/esphome/components/text_sensor/filter.h
index 8a8bc55c8e..ccc52e2770 100644
--- a/esphome/components/text_sensor/filter.h
+++ b/esphome/components/text_sensor/filter.h
@@ -3,6 +3,8 @@
 #include "esphome/core/defines.h"
 #ifdef USE_TEXT_SENSOR_FILTER
 
+#include <array>
+
 #include "esphome/core/component.h"
 #include "esphome/core/helpers.h"
 
@@ -131,6 +133,9 @@ class SubstituteFilter : public Filter {
   FixedVector<Substitution> substitutions_;
 };
 
+/// Non-template helper (implementation in filter.cpp)
+bool map_filter_apply(const Substitution *mappings, size_t count, std::string &value);
+
 /** A filter that maps values from one set to another
  *
  * Uses linear search instead of std::map for typical small datasets (2-20 mappings).
@@ -154,14 +159,23 @@ class SubstituteFilter : public Filter {
  * - Faster for typical ESPHome usage (2-10 mappings common, 20+ rare)
  *
  * Break-even point: ~35-40 mappings, but ESPHome configs rarely exceed 20
+ *
+ * N is set by code generation to match the exact number of mappings configured in YAML.
  */
-class MapFilter : public Filter {
+template<size_t N> class MapFilter : public Filter {
  public:
-  explicit MapFilter(const std::initializer_list<Substitution> &mappings);
-  bool new_value(std::string &value) override;
+  explicit MapFilter(const std::initializer_list<Substitution> &mappings) {
+    size_t i = 0;
+    for (const auto &m : mappings) {
+      if (i >= N)
+        break;
+      this->mappings_[i++] = m;
+    }
+  }
+  bool new_value(std::string &value) override { return map_filter_apply(this->mappings_.data(), N, value); }
 
  protected:
-  FixedVector<Substitution> mappings_;
+  std::array<Substitution, N> mappings_{};
 };
 
 }  // namespace esphome::text_sensor