Convert C++ std::shared_ptr(NULL) to JS null (#85)

* convert C++ std::shared_ptr(NULL) to JS null

* update the changelog

CHANGES-JSE

@@ -7,6 +7,10 @@ the issue number to the end of the URL: https://github.com/swig/swig/issues/
 Version 5.0.6
 ===========================
 
+2024-10-16: mmomtchev
+            [JavaScript] Fix [mmomtchev/swig#84](https://github.com/mmomtchev/swig/issues/84),
+            `std::shared_ptr` typemaps do not work with `NULL` values
+
 2024-10-16: mmomtchev
             [JavaScript] Use TypeScript type branding for representing C/C++
             opaque objects and allow `null` values

Examples/test-suite/cpp11_shared_ptr_nullptr_in_containers.i

@@ -24,7 +24,7 @@ public:
 
 %}
 
-%template() std::vector<std::shared_ptr<C> >;
+%template(c_array) std::vector<std::shared_ptr<C> >;
 
 %inline %{
 

Examples/test-suite/javascript/cpp11_shared_ptr_nullptr_in_containers_runme.js

@@ -0,0 +1,21 @@
+var cpp11_shared_ptr_nullptr_in_containers = require('cpp11_shared_ptr_nullptr_in_containers');
+
+const a = /* await */(cpp11_shared_ptr_nullptr_in_containers.ret_vec_c_shared_ptr());
+if (!(a instanceof cpp11_shared_ptr_nullptr_in_containers.c_array))
+  throw new Error('Did not receive an array');
+
+if (/* await */(a.size()) !== 3)
+  throw new Error('Expected 3 elements');
+
+
+const values = [0, null, 2];
+for (const i in values) {
+  const el = /* await */(a.get(+i));
+  if (values[i] === null) {
+    if (el !== null)
+      throw new Error(`${i} element is not null`);
+  } else {
+    if (/* await */(el.get_m()) !== values[i])
+      throw new Error(`${i} element is not ${values[i]}`);
+  }
+}

Lib/javascript/napi/std_shared_ptr.i

@@ -43,20 +43,24 @@
 // (the *& trick is needed because $1 is a SwigValueWrapper)
 %typemap(out) std::shared_ptr<CONST TYPE> {
   %set_output(SWIG_NewPointerObj(const_cast<TYPE *>($1.get()), $descriptor(TYPE *), SWIG_POINTER_OWN | %newpointer_flags));
-  auto *owner = new std::shared_ptr<CONST TYPE>(*&$1);
-  auto finalizer = new SWIG_NAPI_Finalizer([owner](){
-    delete owner;
-  });
-  SWIG_NAPI_SetFinalizer(env, $result, finalizer);
+  if (!$result.IsNull()) {
+    auto *owner = new std::shared_ptr<CONST TYPE>(*&$1);
+    auto finalizer = new SWIG_NAPI_Finalizer([owner](){
+      delete owner;
+    });
+    SWIG_NAPI_SetFinalizer(env, $result, finalizer);
+  }
 }
 
 %typemap(out) std::shared_ptr<CONST TYPE> & {
   %set_output(SWIG_NewPointerObj(const_cast<TYPE *>($1->get()), $descriptor(TYPE *), $owner | %newpointer_flags));
-  auto owner = new std::shared_ptr<CONST TYPE>(*$1);
-  auto finalizer = new SWIG_NAPI_Finalizer([owner](){
-    delete owner;
-  });
-  SWIG_NAPI_SetFinalizer(env, $result, finalizer);
+  if (!$result.IsNull()) {
+    auto owner = new std::shared_ptr<CONST TYPE>(*$1);
+    auto finalizer = new SWIG_NAPI_Finalizer([owner](){
+      delete owner;
+    });
+    SWIG_NAPI_SetFinalizer(env, $result, finalizer);
+  }
 }
 
 %typemap(in, numinputs=0) std::shared_ptr<CONST TYPE> &OUTPUT {