From f0e84e4933b0d4120cd30ac1e0054ae67319f773 Mon Sep 17 00:00:00 2001
From: Benoit Blanchon <git@benoitblanchon.fr>
Date: Mon, 7 Apr 2025 09:46:02 +0200
Subject: [PATCH] Fix support for `const char[]`

Fixes #2166
---
 CHANGELOG.md                                  |  1 +
 extras/tests/Misc/CMakeLists.txt              |  1 +
 extras/tests/Misc/StringAdapters.cpp          |  1 +
 extras/tests/Misc/issue2166.cpp               | 22 +++++++++++++++++++
 .../Strings/Adapters/RamString.hpp            | 10 +++++++++
 5 files changed, 35 insertions(+)
 create mode 100644 extras/tests/Misc/issue2166.cpp

diff --git a/CHANGELOG.md b/CHANGELOG.md
index ff2d14ab..ccefd7c8 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,7 @@ HEAD
 ----
 
 * Optimize storage of tiny strings (up to 3 characters)
+* Fix support for `const char[]` (issue #2166)
 
 v7.3.1 (2025-02-27)
 ------
diff --git a/extras/tests/Misc/CMakeLists.txt b/extras/tests/Misc/CMakeLists.txt
index 4edd2ba5..05be1ca8 100644
--- a/extras/tests/Misc/CMakeLists.txt
+++ b/extras/tests/Misc/CMakeLists.txt
@@ -7,6 +7,7 @@ add_executable(MiscTests
 	conflicts.cpp
 	issue1967.cpp
 	issue2129.cpp
+	issue2166.cpp
 	JsonString.cpp
 	NoArduinoHeader.cpp
 	printable.cpp
diff --git a/extras/tests/Misc/StringAdapters.cpp b/extras/tests/Misc/StringAdapters.cpp
index c2ebf1fd..99178975 100644
--- a/extras/tests/Misc/StringAdapters.cpp
+++ b/extras/tests/Misc/StringAdapters.cpp
@@ -128,6 +128,7 @@ TEST_CASE("IsString<T>") {
   CHECK(IsString<const __FlashStringHelper*>::value == true);
   CHECK(IsString<const char*>::value == true);
   CHECK(IsString<const char[8]>::value == true);
+  CHECK(IsString<const char[]>::value == true);
   CHECK(IsString<::String>::value == true);
   CHECK(IsString<::StringSumHelper>::value == true);
   CHECK(IsString<const EmptyStruct*>::value == false);
diff --git a/extras/tests/Misc/issue2166.cpp b/extras/tests/Misc/issue2166.cpp
new file mode 100644
index 00000000..f068bd62
--- /dev/null
+++ b/extras/tests/Misc/issue2166.cpp
@@ -0,0 +1,22 @@
+// ArduinoJson - https://arduinojson.org
+// Copyright © 2014-2025, Benoit BLANCHON
+// MIT License
+
+#include <ArduinoJson.h>
+#include <catch.hpp>
+
+struct CCLASS {
+  static const char mszKey[];
+};
+
+TEST_CASE("Issue #2166") {
+  JsonDocument doc;
+  doc[CCLASS::mszKey] = 12;
+  REQUIRE(doc.as<std::string>() == "{\"test3\":12}");
+
+  JsonObject obj = doc.to<JsonObject>();
+  obj[CCLASS::mszKey] = 12;
+  REQUIRE(doc.as<std::string>() == "{\"test3\":12}");
+}
+
+const char CCLASS::mszKey[] = "test3";
diff --git a/src/ArduinoJson/Strings/Adapters/RamString.hpp b/src/ArduinoJson/Strings/Adapters/RamString.hpp
index deb09980..c269ffb7 100644
--- a/src/ArduinoJson/Strings/Adapters/RamString.hpp
+++ b/src/ArduinoJson/Strings/Adapters/RamString.hpp
@@ -76,6 +76,16 @@ struct StringAdapter<TChar*, enable_if_t<IsChar<TChar>::value>> {
   }
 };
 
+template <typename TChar>
+struct StringAdapter<TChar[], enable_if_t<IsChar<TChar>::value>> {
+  using AdaptedString = RamString;
+
+  static AdaptedString adapt(const TChar* p) {
+    auto str = reinterpret_cast<const char*>(p);
+    return AdaptedString(str, str ? ::strlen(str) : 0);
+  }
+};
+
 template <size_t N>
 struct StringAdapter<const char (&)[N]> {
   using AdaptedString = RamString;