Deprecate containsKey() in favor of doc["key"].is<T>()

See #2121

CHANGELOG.md

@@ -9,6 +9,7 @@ HEAD
 * Reduce the slot size (see table below)
 * Improve message when user forgets third arg of `serializeJson()` et al.
 * Set `ARDUINOJSON_USE_DOUBLE` to `0` by default on 8-bit architectures
+* Deprecate `containsKey()` in favor of `doc["key"].is<T>()`
 
 | Architecture | before   | after    |
 |--------------|----------|----------|
@@ -16,6 +17,25 @@ HEAD
 | 32-bit       | 16 bytes | 8 bytes  |
 | 64-bit       | 24 bytes | 16 bytes |
 
+> ### BREAKING CHANGES
+>
+> After being on the death row for years, the `containsKey()` method has finally been deprecated.
+> You should replace `doc.containsKey("key")` with `doc["key"].is<T>()`, which not only checks that the key exists but also that the value is of the expected type.
+>
+> ```cpp
+> // Before
+> if (doc.containsKey("value")) {
+>   int value = doc["value"];
+>   // ...
+> }
+>
+> // After
+> if (doc["value"].is<int>()) {
+>   int value = doc["value"];
+>   // ...
+> }
+> ```
+
 v7.1.0 (2024-06-27)
 ------
 

extras/tests/Deprecated/CMakeLists.txt

@@ -16,9 +16,10 @@ endif()
 
 add_executable(DeprecatedTests
 	add.cpp
+	BasicJsonDocument.cpp
+	containsKey.cpp
 	createNestedArray.cpp
 	createNestedObject.cpp
-	BasicJsonDocument.cpp
 	DynamicJsonDocument.cpp
 	macros.cpp
 	memoryUsage.cpp

extras/tests/Deprecated/containsKey.cpp

@@ -0,0 +1,210 @@
+// ArduinoJson - https://arduinojson.org
+// Copyright © 2014-2024, Benoit BLANCHON
+// MIT License
+
+#include <ArduinoJson.h>
+#include <catch.hpp>
+
+#include "Literals.hpp"
+
+TEST_CASE("JsonDocument::containsKey()") {
+  JsonDocument doc;
+
+  SECTION("returns true on object") {
+    doc["hello"] = "world";
+
+    REQUIRE(doc.containsKey("hello") == true);
+  }
+
+  SECTION("returns true when value is null") {
+    doc["hello"] = static_cast<const char*>(0);
+
+    REQUIRE(doc.containsKey("hello") == true);
+  }
+
+  SECTION("returns true when key is a std::string") {
+    doc["hello"] = "world";
+
+    REQUIRE(doc.containsKey("hello"_s) == true);
+  }
+
+  SECTION("returns false  on object") {
+    doc["world"] = "hello";
+
+    REQUIRE(doc.containsKey("hello") == false);
+  }
+
+  SECTION("returns false on array") {
+    doc.add("hello");
+
+    REQUIRE(doc.containsKey("hello") == false);
+  }
+
+  SECTION("returns false on null") {
+    REQUIRE(doc.containsKey("hello") == false);
+  }
+
+  SECTION("support JsonVariant") {
+    doc["hello"] = "world";
+    doc["key"] = "hello";
+
+    REQUIRE(doc.containsKey(doc["key"]) == true);
+    REQUIRE(doc.containsKey(doc["foo"]) == false);
+  }
+}
+
+TEST_CASE("MemberProxy::containsKey()") {
+  JsonDocument doc;
+  auto mp = doc["hello"];
+
+  SECTION("containsKey(const char*)") {
+    mp["key"] = "value";
+
+    REQUIRE(mp.containsKey("key") == true);
+    REQUIRE(mp.containsKey("key") == true);
+  }
+
+  SECTION("containsKey(std::string)") {
+    mp["key"] = "value";
+
+    REQUIRE(mp.containsKey("key"_s) == true);
+    REQUIRE(mp.containsKey("key"_s) == true);
+  }
+}
+
+TEST_CASE("JsonObject::containsKey()") {
+  JsonDocument doc;
+  JsonObject obj = doc.to<JsonObject>();
+  obj["hello"] = 42;
+
+  SECTION("returns true only if key is present") {
+    REQUIRE(false == obj.containsKey("world"));
+    REQUIRE(true == obj.containsKey("hello"));
+  }
+
+  SECTION("returns false after remove()") {
+    obj.remove("hello");
+
+    REQUIRE(false == obj.containsKey("hello"));
+  }
+
+#ifdef HAS_VARIABLE_LENGTH_ARRAY
+  SECTION("key is a VLA") {
+    size_t i = 16;
+    char vla[i];
+    strcpy(vla, "hello");
+
+    REQUIRE(true == obj.containsKey(vla));
+  }
+#endif
+
+  SECTION("key is a JsonVariant") {
+    doc["key"] = "hello";
+    REQUIRE(true == obj.containsKey(obj["key"]));
+    REQUIRE(false == obj.containsKey(obj["hello"]));
+  }
+
+  SECTION("std::string") {
+    REQUIRE(true == obj.containsKey("hello"_s));
+  }
+
+  SECTION("unsigned char[]") {
+    unsigned char key[] = "hello";
+    REQUIRE(true == obj.containsKey(key));
+  }
+}
+
+TEST_CASE("JsonObjectConst::containsKey()") {
+  JsonDocument doc;
+  doc["hello"] = 42;
+  auto obj = doc.as<JsonObjectConst>();
+
+  SECTION("supports const char*") {
+    REQUIRE(false == obj.containsKey("world"));
+    REQUIRE(true == obj.containsKey("hello"));
+  }
+
+  SECTION("supports std::string") {
+    REQUIRE(false == obj.containsKey("world"_s));
+    REQUIRE(true == obj.containsKey("hello"_s));
+  }
+
+#ifdef HAS_VARIABLE_LENGTH_ARRAY
+  SECTION("supports VLA") {
+    size_t i = 16;
+    char vla[i];
+    strcpy(vla, "hello");
+
+    REQUIRE(true == obj.containsKey(vla));
+  }
+#endif
+
+  SECTION("supports JsonVariant") {
+    doc["key"] = "hello";
+    REQUIRE(true == obj.containsKey(obj["key"]));
+    REQUIRE(false == obj.containsKey(obj["hello"]));
+  }
+}
+
+TEST_CASE("JsonVariant::containsKey()") {
+  JsonDocument doc;
+  JsonVariant var = doc.to<JsonVariant>();
+
+  SECTION("returns false is unbound") {
+    CHECK_FALSE(JsonVariant().containsKey("hello"));
+  }
+
+  SECTION("containsKey(const char*)") {
+    var["hello"] = "world";
+
+    REQUIRE(var.containsKey("hello") == true);
+    REQUIRE(var.containsKey("world") == false);
+  }
+
+  SECTION("containsKey(std::string)") {
+    var["hello"] = "world";
+
+    REQUIRE(var.containsKey("hello"_s) == true);
+    REQUIRE(var.containsKey("world"_s) == false);
+  }
+
+  SECTION("containsKey(JsonVariant)") {
+    var["hello"] = "world";
+    var["key"] = "hello";
+
+    REQUIRE(var.containsKey(doc["key"]) == true);
+    REQUIRE(var.containsKey(doc["foo"]) == false);
+  }
+}
+
+TEST_CASE("JsonVariantConst::containsKey()") {
+  JsonDocument doc;
+  doc["hello"] = "world";
+  JsonVariantConst var = doc.as<JsonVariant>();
+
+  SECTION("support const char*") {
+    REQUIRE(var.containsKey("hello") == true);
+    REQUIRE(var.containsKey("world") == false);
+  }
+
+  SECTION("support std::string") {
+    REQUIRE(var.containsKey("hello"_s) == true);
+    REQUIRE(var.containsKey("world"_s) == false);
+  }
+
+#ifdef HAS_VARIABLE_LENGTH_ARRAY
+  SECTION("supports VLA") {
+    size_t i = 16;
+    char vla[i];
+    strcpy(vla, "hello");
+
+    REQUIRE(true == var.containsKey(vla));
+  }
+#endif
+
+  SECTION("support JsonVariant") {
+    doc["key"] = "hello";
+    REQUIRE(var.containsKey(var["key"]) == true);
+    REQUIRE(var.containsKey(var["foo"]) == false);
+  }
+}

extras/tests/JsonDocument/CMakeLists.txt

@@ -9,7 +9,6 @@ add_executable(JsonDocumentTests
 	clear.cpp
 	compare.cpp
 	constructor.cpp
-	containsKey.cpp
 	ElementProxy.cpp
 	isNull.cpp
 	issue1120.cpp

extras/tests/JsonDocument/MemberProxy.cpp

@@ -93,25 +93,6 @@ TEST_CASE("MemberProxy::operator==()") {
   }
 }
 
-TEST_CASE("MemberProxy::containsKey()") {
-  JsonDocument doc;
-  MemberProxy mp = doc["hello"];
-
-  SECTION("containsKey(const char*)") {
-    mp["key"] = "value";
-
-    REQUIRE(mp.containsKey("key") == true);
-    REQUIRE(mp.containsKey("key") == true);
-  }
-
-  SECTION("containsKey(std::string)") {
-    mp["key"] = "value";
-
-    REQUIRE(mp.containsKey("key"_s) == true);
-    REQUIRE(mp.containsKey("key"_s) == true);
-  }
-}
-
 TEST_CASE("MemberProxy::operator|()") {
   JsonDocument doc;
 

extras/tests/JsonDocument/containsKey.cpp

@@ -1,54 +0,0 @@
-// ArduinoJson - https://arduinojson.org
-// Copyright © 2014-2024, Benoit BLANCHON
-// MIT License
-
-#include <ArduinoJson.h>
-#include <catch.hpp>
-
-#include "Literals.hpp"
-
-TEST_CASE("JsonDocument::containsKey()") {
-  JsonDocument doc;
-
-  SECTION("returns true on object") {
-    doc["hello"] = "world";
-
-    REQUIRE(doc.containsKey("hello") == true);
-  }
-
-  SECTION("returns true when value is null") {
-    doc["hello"] = static_cast<const char*>(0);
-
-    REQUIRE(doc.containsKey("hello") == true);
-  }
-
-  SECTION("returns true when key is a std::string") {
-    doc["hello"] = "world";
-
-    REQUIRE(doc.containsKey("hello"_s) == true);
-  }
-
-  SECTION("returns false  on object") {
-    doc["world"] = "hello";
-
-    REQUIRE(doc.containsKey("hello") == false);
-  }
-
-  SECTION("returns false on array") {
-    doc.add("hello");
-
-    REQUIRE(doc.containsKey("hello") == false);
-  }
-
-  SECTION("returns false on null") {
-    REQUIRE(doc.containsKey("hello") == false);
-  }
-
-  SECTION("support JsonVariant") {
-    doc["hello"] = "world";
-    doc["key"] = "hello";
-
-    REQUIRE(doc.containsKey(doc["key"]) == true);
-    REQUIRE(doc.containsKey(doc["foo"]) == false);
-  }
-}

extras/tests/JsonObject/CMakeLists.txt

@@ -5,7 +5,6 @@
 add_executable(JsonObjectTests
 	clear.cpp
 	compare.cpp
-	containsKey.cpp
 	equals.cpp
 	isNull.cpp
 	iterator.cpp

extras/tests/JsonObject/containsKey.cpp

@@ -1,39 +0,0 @@
-// ArduinoJson - https://arduinojson.org
-// Copyright © 2014-2024, Benoit BLANCHON
-// MIT License
-
-#include <ArduinoJson.h>
-#include <catch.hpp>
-
-TEST_CASE("JsonObject::containsKey()") {
-  JsonDocument doc;
-  JsonObject obj = doc.to<JsonObject>();
-  obj["hello"] = 42;
-
-  SECTION("returns true only if key is present") {
-    REQUIRE(false == obj.containsKey("world"));
-    REQUIRE(true == obj.containsKey("hello"));
-  }
-
-  SECTION("returns false after remove()") {
-    obj.remove("hello");
-
-    REQUIRE(false == obj.containsKey("hello"));
-  }
-
-#ifdef HAS_VARIABLE_LENGTH_ARRAY
-  SECTION("key is a VLA") {
-    size_t i = 16;
-    char vla[i];
-    strcpy(vla, "hello");
-
-    REQUIRE(true == obj.containsKey(vla));
-  }
-#endif
-
-  SECTION("key is a JsonVariant") {
-    doc["key"] = "hello";
-    REQUIRE(true == obj.containsKey(obj["key"]));
-    REQUIRE(false == obj.containsKey(obj["hello"]));
-  }
-}

extras/tests/JsonObject/std_string.cpp

@@ -34,13 +34,6 @@ TEST_CASE("std::string") {
     REQUIRE("value"_s == obj["key"_s]);
   }
 
-  SECTION("containsKey()") {
-    char json[] = "{\"key\":\"value\"}";
-    deserializeJson(doc, json);
-    JsonObject obj = doc.as<JsonObject>();
-    REQUIRE(true == obj.containsKey("key"_s));
-  }
-
   SECTION("remove()") {
     JsonObject obj = doc.to<JsonObject>();
     obj["key"] = "value";

extras/tests/JsonObjectConst/CMakeLists.txt

@@ -3,7 +3,6 @@
 # MIT License
 
 add_executable(JsonObjectConstTests
-	containsKey.cpp
 	equals.cpp
 	isNull.cpp
 	iterator.cpp

extras/tests/JsonObjectConst/containsKey.cpp

@@ -1,40 +0,0 @@
-// ArduinoJson - https://arduinojson.org
-// Copyright © 2014-2024, Benoit BLANCHON
-// MIT License
-
-#include <ArduinoJson.h>
-#include <catch.hpp>
-
-#include "Literals.hpp"
-
-TEST_CASE("JsonObjectConst::containsKey()") {
-  JsonDocument doc;
-  doc["hello"] = 42;
-  auto obj = doc.as<JsonObjectConst>();
-
-  SECTION("supports const char*") {
-    REQUIRE(false == obj.containsKey("world"));
-    REQUIRE(true == obj.containsKey("hello"));
-  }
-
-  SECTION("supports std::string") {
-    REQUIRE(false == obj.containsKey("world"_s));
-    REQUIRE(true == obj.containsKey("hello"_s));
-  }
-
-#ifdef HAS_VARIABLE_LENGTH_ARRAY
-  SECTION("supports VLA") {
-    size_t i = 16;
-    char vla[i];
-    strcpy(vla, "hello");
-
-    REQUIRE(true == obj.containsKey(vla));
-  }
-#endif
-
-  SECTION("supports JsonVariant") {
-    doc["key"] = "hello";
-    REQUIRE(true == obj.containsKey(obj["key"]));
-    REQUIRE(false == obj.containsKey(obj["hello"]));
-  }
-}

extras/tests/JsonVariant/CMakeLists.txt

@@ -7,7 +7,6 @@ add_executable(JsonVariantTests
 	as.cpp
 	clear.cpp
 	compare.cpp
-	containsKey.cpp
 	converters.cpp
 	copy.cpp
 	is.cpp

extras/tests/JsonVariant/containsKey.cpp

@@ -1,36 +0,0 @@
-// ArduinoJson - https://arduinojson.org
-// Copyright © 2014-2024, Benoit BLANCHON
-// MIT License
-
-#include <ArduinoJson.h>
-#include <stdint.h>
-#include <catch.hpp>
-
-#include "Literals.hpp"
-
-TEST_CASE("JsonVariant::containsKey()") {
-  JsonDocument doc;
-  JsonVariant var = doc.to<JsonVariant>();
-
-  SECTION("containsKey(const char*)") {
-    var["hello"] = "world";
-
-    REQUIRE(var.containsKey("hello") == true);
-    REQUIRE(var.containsKey("world") == false);
-  }
-
-  SECTION("containsKey(std::string)") {
-    var["hello"] = "world";
-
-    REQUIRE(var.containsKey("hello"_s) == true);
-    REQUIRE(var.containsKey("world"_s) == false);
-  }
-
-  SECTION("containsKey(JsonVariant)") {
-    var["hello"] = "world";
-    var["key"] = "hello";
-
-    REQUIRE(var.containsKey(doc["key"]) == true);
-    REQUIRE(var.containsKey(doc["foo"]) == false);
-  }
-}

extras/tests/JsonVariant/unbound.cpp

@@ -73,10 +73,6 @@ TEST_CASE("Unbound JsonVariant") {
     CHECK_FALSE(variant["key"_s].set(1));
   }
 
-  SECTION("containsKey()") {
-    CHECK_FALSE(variant.containsKey("hello"));
-  }
-
   SECTION("remove()") {
     variant.remove(0);
     variant.remove("hello");

extras/tests/JsonVariantConst/CMakeLists.txt

@@ -4,7 +4,6 @@
 
 add_executable(JsonVariantConstTests
 	as.cpp
-	containsKey.cpp
 	is.cpp
 	isnull.cpp
 	nesting.cpp

extras/tests/JsonVariantConst/containsKey.cpp

@@ -1,41 +0,0 @@
-// ArduinoJson - https://arduinojson.org
-// Copyright © 2014-2024, Benoit BLANCHON
-// MIT License
-
-#include <ArduinoJson.h>
-#include <stdint.h>
-#include <catch.hpp>
-
-#include "Literals.hpp"
-
-TEST_CASE("JsonVariantConst::containsKey()") {
-  JsonDocument doc;
-  doc["hello"] = "world";
-  JsonVariantConst var = doc.as<JsonVariant>();
-
-  SECTION("support const char*") {
-    REQUIRE(var.containsKey("hello") == true);
-    REQUIRE(var.containsKey("world") == false);
-  }
-
-  SECTION("support std::string") {
-    REQUIRE(var.containsKey("hello"_s) == true);
-    REQUIRE(var.containsKey("world"_s) == false);
-  }
-
-#ifdef HAS_VARIABLE_LENGTH_ARRAY
-  SECTION("supports VLA") {
-    size_t i = 16;
-    char vla[i];
-    strcpy(vla, "hello");
-
-    REQUIRE(true == var.containsKey(vla));
-  }
-#endif
-
-  SECTION("support JsonVariant") {
-    doc["key"] = "hello";
-    REQUIRE(var.containsKey(var["key"]) == true);
-    REQUIRE(var.containsKey(var["foo"]) == false);
-  }
-}

extras/tests/Misc/unsigned_char.cpp

@@ -176,15 +176,6 @@ TEST_CASE("unsigned char[]") {
     }
 #endif
 
-    SECTION("containsKey()") {
-      unsigned char key[] = "hello";
-
-      JsonDocument doc;
-      deserializeJson(doc, "{\"hello\":\"world\"}");
-      JsonObject obj = doc.as<JsonObject>();
-      REQUIRE(true == obj.containsKey(key));
-    }
-
     SECTION("remove()") {
       unsigned char key[] = "hello";
 

src/ArduinoJson/Document/JsonDocument.hpp

@@ -150,24 +150,27 @@ class JsonDocument : public detail::VariantOperators<const JsonDocument&> {
     return getVariant().template to<T>();
   }
 
-  // Returns true if the root object contains the specified key.
+  // DEPRECATED: use obj["key"].is<T>() instead
   // https://arduinojson.org/v7/api/jsondocument/containskey/
   template <typename TChar>
+  ARDUINOJSON_DEPRECATED("use doc[\"key\"].is<T>() instead")
   bool containsKey(TChar* key) const {
     return data_.getMember(detail::adaptString(key), &resources_) != 0;
   }
 
-  // Returns true if the root object contains the specified key.
+  // DEPRECATED: use obj[key].is<T>() instead
   // https://arduinojson.org/v7/api/jsondocument/containskey/
   template <typename TString>
+  ARDUINOJSON_DEPRECATED("use doc[key].is<T>() instead")
   detail::enable_if_t<detail::IsString<TString>::value, bool> containsKey(
       const TString& key) const {
     return data_.getMember(detail::adaptString(key), &resources_) != 0;
   }
 
-  // Returns true if the root object contains the specified key.
+  // DEPRECATED: use obj[key].is<T>() instead
   // https://arduinojson.org/v7/api/jsondocument/containskey/
   template <typename TVariant>
+  ARDUINOJSON_DEPRECATED("use doc[key].is<T>() instead")
   detail::enable_if_t<detail::IsVariant<TVariant>::value, bool> containsKey(
       const TVariant& key) const {
     return containsKey(key.template as<const char*>());

src/ArduinoJson/Object/JsonObject.hpp

@@ -161,27 +161,30 @@ class JsonObject : public detail::VariantOperators<JsonObject> {
                                      resources_);
   }
 
-  // Returns true if the object contains the specified key.
+  // DEPRECATED: use obj[key].is<T>() instead
   // https://arduinojson.org/v7/api/jsonobject/containskey/
   template <typename TString>
+  ARDUINOJSON_DEPRECATED("use obj[key].is<T>() instead")
   detail::enable_if_t<detail::IsString<TString>::value, bool> containsKey(
       const TString& key) const {
     return detail::ObjectData::getMember(data_, detail::adaptString(key),
                                          resources_) != 0;
   }
 
-  // Returns true if the object contains the specified key.
+  // DEPRECATED: use obj["key"].is<T>() instead
   // https://arduinojson.org/v7/api/jsonobject/containskey/
   template <typename TChar>
+  ARDUINOJSON_DEPRECATED("use obj[\"key\"].is<T>() instead")
   detail::enable_if_t<detail::IsString<TChar*>::value, bool> containsKey(
       TChar* key) const {
     return detail::ObjectData::getMember(data_, detail::adaptString(key),
                                          resources_) != 0;
   }
 
-  // Returns true if the object contains the specified key.
+  // DEPRECATED: use obj[key].is<T>() instead
   // https://arduinojson.org/v7/api/jsonobject/containskey/
   template <typename TVariant>
+  ARDUINOJSON_DEPRECATED("use obj[key].is<T>() instead")
   detail::enable_if_t<detail::IsVariant<TVariant>::value, bool> containsKey(
       const TVariant& key) const {
     return containsKey(key.template as<const char*>());

src/ArduinoJson/Object/JsonObjectConst.hpp

@@ -68,26 +68,29 @@ class JsonObjectConst : public detail::VariantOperators<JsonObjectConst> {
     return iterator();
   }
 
-  // Returns true if the object contains the specified key.
+  // DEPRECATED: use obj[key].is<T>() instead
   // https://arduinojson.org/v7/api/jsonobjectconst/containskey/
   template <typename TString>
+  ARDUINOJSON_DEPRECATED("use obj[key].is<T>() instead")
   detail::enable_if_t<detail::IsString<TString>::value, bool> containsKey(
       const TString& key) const {
     return detail::ObjectData::getMember(data_, detail::adaptString(key),
                                          resources_) != 0;
   }
 
-  // Returns true if the object contains the specified key.
+  // DEPRECATED: use obj["key"].is<T>() instead
   // https://arduinojson.org/v7/api/jsonobjectconst/containskey/
   template <typename TChar>
+  ARDUINOJSON_DEPRECATED("use obj[\"key\"].is<T>() instead")
   bool containsKey(TChar* key) const {
     return detail::ObjectData::getMember(data_, detail::adaptString(key),
                                          resources_) != 0;
   }
 
-  // Returns true if the object contains the specified key.
+  // DEPRECATED: use obj[key].is<T>() instead
   // https://arduinojson.org/v7/api/jsonobjectconst/containskey/
   template <typename TVariant>
+  ARDUINOJSON_DEPRECATED("use obj[key].is<T>() instead")
   detail::enable_if_t<detail::IsVariant<TVariant>::value, bool> containsKey(
       const TVariant& key) const {
     return containsKey(key.template as<const char*>());

src/ArduinoJson/Variant/JsonVariantConst.hpp

@@ -139,25 +139,30 @@ class JsonVariantConst : public detail::VariantTag,
       return operator[](key.template as<const char*>());
   }
 
-  // Returns true if tge object contains the specified key.
+  // DEPRECATED: use obj[key].is<T>() instead
   // https://arduinojson.org/v7/api/jsonvariantconst/containskey/
   template <typename TString>
+  ARDUINOJSON_DEPRECATED("use var[key].is<T>() instead")
   detail::enable_if_t<detail::IsString<TString>::value, bool> containsKey(
       const TString& key) const {
     return detail::VariantData::getMember(getData(), detail::adaptString(key),
                                           resources_) != 0;
   }
 
-  // Returns true if tge object contains the specified key.
+  // DEPRECATED: use obj["key"].is<T>() instead
   // https://arduinojson.org/v7/api/jsonvariantconst/containskey/
   template <typename TChar>
+  ARDUINOJSON_DEPRECATED("use obj[\"key\"].is<T>() instead")
   detail::enable_if_t<detail::IsString<TChar*>::value, bool> containsKey(
       TChar* key) const {
     return detail::VariantData::getMember(getData(), detail::adaptString(key),
                                           resources_) != 0;
   }
 
+  // DEPRECATED: use obj[key].is<T>() instead
+  // https://arduinojson.org/v7/api/jsonvariantconst/containskey/
   template <typename TVariant>
+  ARDUINOJSON_DEPRECATED("use var[key].is<T>() instead")
   detail::enable_if_t<detail::IsVariant<TVariant>::value, bool> containsKey(
       const TVariant& key) const {
     return containsKey(key.template as<const char*>());

src/ArduinoJson/Variant/VariantRefBase.hpp

@@ -165,20 +165,23 @@ class VariantRefBase : public VariantTag {
   // https://arduinojson.org/v7/api/jsonvariant/subscript/
   ElementProxy<TDerived> operator[](size_t index) const;
 
-  // Returns true if the object contains the specified key.
+  // DEPRECATED: use obj[key].is<T>() instead
   // https://arduinojson.org/v7/api/jsonvariant/containskey/
   template <typename TString>
+  ARDUINOJSON_DEPRECATED("use obj[key].is<T>() instead")
   enable_if_t<IsString<TString>::value, bool> containsKey(
       const TString& key) const;
 
-  // Returns true if the object contains the specified key.
+  // DEPRECATED: use obj["key"].is<T>() instead
   // https://arduinojson.org/v7/api/jsonvariant/containskey/
   template <typename TChar>
+  ARDUINOJSON_DEPRECATED("use obj[\"key\"].is<T>() instead")
   enable_if_t<IsString<TChar*>::value, bool> containsKey(TChar* key) const;
 
-  // Returns true if the object contains the specified key.
+  // DEPRECATED: use obj[key].is<T>() instead
   // https://arduinojson.org/v7/api/jsonvariant/containskey/
   template <typename TVariant>
+  ARDUINOJSON_DEPRECATED("use obj[key].is<T>() instead")
   enable_if_t<IsVariant<TVariant>::value, bool> containsKey(
       const TVariant& key) const;