Add a stub for shallowCopy()

extras/tests/Deprecated/CMakeLists.txt

@@ -18,6 +18,7 @@ add_executable(DeprecatedTests
 	BasicJsonDocument.cpp
 	DynamicJsonDocument.cpp
 	memoryUsage.cpp
+	shallowCopy.cpp
 	StaticJsonDocument.cpp
 )
 

extras/tests/Deprecated/shallowCopy.cpp

@@ -0,0 +1,14 @@
+// ArduinoJson - https://arduinojson.org
+// Copyright © 2014-2023, Benoit BLANCHON
+// MIT License
+
+#include <ArduinoJson.h>
+#include <catch.hpp>
+
+TEST_CASE("shallowCopy()") {
+  JsonDocument doc1, doc2;
+  doc1["b"] = "c";
+  doc2["a"].shallowCopy(doc1);
+
+  REQUIRE(doc2.as<std::string>() == "{\"a\":{\"b\":\"c\"}}");
+}

src/ArduinoJson/Variant/VariantRefBase.hpp

@@ -227,6 +227,12 @@ class VariantRefBase : public VariantTag {
     return 0;
   }
 
+  // DEPRECATED: performs a deep copy
+  ARDUINOJSON_DEPRECATED("performs a deep copy")
+  void shallowCopy(JsonVariantConst src) const {
+    set(src);
+  }
+
  private:
   TDerived& derived() {
     return static_cast<TDerived&>(*this);