From 7f5409214b66f0b79e8016913397d54b50466137 Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@home-assistant.io>
Date: Fri, 27 Mar 2026 16:14:59 -1000
Subject: [PATCH] Use init_array_from helper for optimal codegen

Uses memcpy for trivially copyable types, element-wise copy otherwise.
ESPHOME_DEBUG_ASSERT catches size mismatches in integration tests.
---
 esphome/components/text_sensor/filter.h |  6 +-----
 esphome/core/helpers.h                  | 15 +++++++++++++++
 tests/integration/fixtures/.gitignore   |  5 +++++
 3 files changed, 21 insertions(+), 5 deletions(-)
 create mode 100644 tests/integration/fixtures/.gitignore

diff --git a/esphome/components/text_sensor/filter.h b/esphome/components/text_sensor/filter.h
index 0366c7fb41b..07832af9e2b 100644
--- a/esphome/components/text_sensor/filter.h
+++ b/esphome/components/text_sensor/filter.h
@@ -165,11 +165,7 @@ bool map_filter_apply(const Substitution *mappings, size_t count, std::string &v
 template<size_t N> class MapFilter : public Filter {
  public:
   explicit MapFilter(const std::initializer_list<Substitution> &mappings) {
-    ESPHOME_DEBUG_ASSERT(mappings.size() == N);
-    size_t i = 0;
-    for (const auto &m : mappings) {
-      this->mappings_[i++] = m;
-    }
+    init_array_from(this->mappings_, mappings);
   }
   bool new_value(std::string &value) override { return map_filter_apply(this->mappings_.data(), N, value); }
 
diff --git a/esphome/core/helpers.h b/esphome/core/helpers.h
index 82c6b3833ce..51feaa57c50 100644
--- a/esphome/core/helpers.h
+++ b/esphome/core/helpers.h
@@ -497,6 +497,21 @@ template<typename T, size_t MAX_CAPACITY = std::numeric_limits<uint16_t>::max()>
   index_type capacity_{0};
 };
 
+/// Initialize a std::array from an initializer_list. Uses memcpy for trivially copyable types (optimal codegen),
+/// falls back to element-wise copy for non-trivially copyable types (e.g. TemplatableValue).
+/// N is set by code generation; ESPHOME_DEBUG_ASSERT catches mismatches in debug/integration tests.
+template<typename T, size_t N> inline void init_array_from(std::array<T, N> &dest, std::initializer_list<T> src) {
+  ESPHOME_DEBUG_ASSERT(src.size() == N);
+  if constexpr (std::is_trivially_copyable_v<T>) {
+    __builtin_memcpy(dest.data(), src.begin(), N * sizeof(T));
+  } else {
+    size_t i = 0;
+    for (const auto &v : src) {
+      dest[i++] = v;
+    }
+  }
+}
+
 /// Fixed-capacity vector - allocates once at runtime, never reallocates
 /// This avoids std::vector template overhead (_M_realloc_insert, _M_default_append)
 /// when size is known at initialization but not at compile time
diff --git a/tests/integration/fixtures/.gitignore b/tests/integration/fixtures/.gitignore
new file mode 100644
index 00000000000..d8b4157aef9
--- /dev/null
+++ b/tests/integration/fixtures/.gitignore
@@ -0,0 +1,5 @@
+# Gitignore settings for ESPHome
+# This is an example and may include too much for your use-case.
+# You can modify this file to suit your needs.
+/.esphome/
+/secrets.yaml