Removed the copy-constructor of JsonDocument (issue #1189)

CHANGELOG.md

@@ -15,6 +15,7 @@ HEAD
 * Added `BasicJsonDocument::garbageCollect()` (issue #1195)
 * Added `StaticJsonDocument::garbageCollect()`
 * Changed copy-constructor of `BasicJsonDocument` to preserve the capacity of the source.
+* Removed copy-constructor of `JsonDocument` (issue #1189)
 
 > ### BREAKING CHANGES
 > 
@@ -37,6 +38,23 @@ HEAD
 > I made this change to get consistent results between copy-constructor and move-constructor, and whether RVO applies or not.
 >
 > If you use the copy-constructor to optimize your documents, you can use `garbageCollect()` or `shrinkToFit()` instead.
+>
+> #### Copy-constructor of `JsonDocument`
+>
+> In previous versions, it was possible to create a function that take a `JsonDocument` by value.
+>
+> ```c++
+> void myFunction(JsonDocument doc) {}
+> ```
+>
+> This function gives the wrong clues because it doesn't receive a copy of the `JsonDocument`, only a sliced version.
+> It worked because the copy constructor copied the internal pointers, but it was an accident.
+>
+> From now, if you need to pass a `JsonDocument` to a function, you must use a reference:
+>
+> ```c++
+> void myFunction(JsonDocument& doc) {}
+> ```
 
 v6.14.1 (2020-01-27)
 -------

extras/tests/Misc/CMakeLists.txt

@@ -20,23 +20,35 @@ set_target_properties(MiscTests PROPERTIES UNITY_BUILD OFF)
 
 add_test(Misc MiscTests)
 
-
-add_executable(Issue978
-	Issue978.cpp
-)
-set_target_properties(Issue978
+macro(build_should_fail target)
+	set_target_properties(${target}
 		PROPERTIES
 	    	EXCLUDE_FROM_ALL TRUE
 	        EXCLUDE_FROM_DEFAULT_BUILD TRUE
 	)
 	add_test(
 		NAME
-		Issue978
+			${target}
 	    COMMAND
-    	${CMAKE_COMMAND} --build . --target Issue978 --config $<CONFIGURATION>
+	    	${CMAKE_COMMAND} --build . --target ${target} --config $<CONFIGURATION>
 	    WORKING_DIRECTORY
 	    	${CMAKE_BINARY_DIR}
 	)
-set_tests_properties(Issue978 
+	set_tests_properties(${target} 
+
+
+
 		PROPERTIES
 			WILL_FAIL TRUE)
+endmacro()
+
+
+add_executable(Issue978
+	Issue978.cpp
+)
+build_should_fail(Issue978)
+
+add_executable(Issue1189
+	Issue1189.cpp
+)
+build_should_fail(Issue1189)

extras/tests/Misc/Issue1189.cpp

@@ -0,0 +1,13 @@
+// ArduinoJson - arduinojson.org
+// Copyright Benoit Blanchon 2014-2020
+// MIT License
+
+#include <ArduinoJson.h>
+
+// a function should not be able to get a JsonDocument by value
+void f(JsonDocument) {}
+
+int main() {
+  DynamicJsonDocument doc(1024);
+  f(doc);
+}

src/ArduinoJson/Document/JsonDocument.hpp

@@ -319,6 +319,10 @@ class JsonDocument : public Visitable {
 
   MemoryPool _pool;
   VariantData _data;
+
+ private:
+  JsonDocument(const JsonDocument&);
+  JsonDocument& operator=(const JsonDocument&);
 };
 
 }  // namespace ARDUINOJSON_NAMESPACE