Macro NODE_API_MODULE doesn't work with namespace in regfunc

[ikokostya]

Environment info

• Node.js version: v10.0.0
• node-addon-api version: 1.2.0

Steps to reproduce

Wrap functions from hello example to namespace:

diff --git a/1_hello_world/node-addon-api/hello.cc b/1_hello_world/node-addon-api/hello.cc
index 0957f53..f00bb77 100644
--- a/1_hello_world/node-addon-api/hello.cc
+++ b/1_hello_world/node-addon-api/hello.cc
@@ -1,5 +1,7 @@
 #include <napi.h>
 
+namespace node_lib {
+
 Napi::String Method(const Napi::CallbackInfo& info) {
   Napi::Env env = info.Env();
   return Napi::String::New(env, "world");
@@ -11,4 +13,6 @@ Napi::Object Init(Napi::Env env, Napi::Object exports) {
   return exports;
 }
 
-NODE_API_MODULE(hello, Init)
+}
+
+NODE_API_MODULE(hello, node_lib::Init)

Actual behavior

Compilation error

gyp info spawn make
gyp info spawn args [ 'BUILDTYPE=Release', '-C', 'build' ]
make: Entering directory '/home/kostya/proj/abi-stable-node-addon-examples/1_hello_world/node-addon-api/build'
  CXX(target) Release/obj.target/hello/hello.o
In file included from /home/kostya/proj/abi-stable-node-addon-examples/1_hello_world/node-addon-api/node_modules/node-addon-api/napi.h:1487:0,
                 from ../hello.cc:1:
/home/kostya/proj/abi-stable-node-addon-examples/1_hello_world/node-addon-api/node_modules/node-addon-api/napi-inl.h:159:14: error: ‘__napi_node_lib’ has not been declared
   napi_value __napi_ ## regfunc(napi_env env,             \
              ^
../hello.cc:18:1: note: in expansion of macro ‘NODE_API_MODULE’
 NODE_API_MODULE(hello, node_lib::Init)
 ^
In file included from /home/kostya/proj/abi-stable-node-addon-examples/1_hello_world/node-addon-api/node_modules/node-addon-api/napi.h:4:0,
                 from ../hello.cc:1:
/home/kostya/proj/abi-stable-node-addon-examples/1_hello_world/node-addon-api/node_modules/node-addon-api/napi-inl.h:163:24: error: ‘__napi_node_lib’ has not been declared
   NAPI_MODULE(modname, __napi_ ## regfunc);
                        ^
/home/kostya/.node-gyp/10.0.0/include/node/node_api.h:83:7: note: in definition of macro ‘NAPI_MODULE_X’
       regfunc,                                                        \
       ^
/home/kostya/proj/abi-stable-node-addon-examples/1_hello_world/node-addon-api/node_modules/node-addon-api/napi-inl.h:163:3: note: in expansion of macro ‘NAPI_MODULE’
   NAPI_MODULE(modname, __napi_ ## regfunc);
   ^
../hello.cc:18:1: note: in expansion of macro ‘NODE_API_MODULE’
 NODE_API_MODULE(hello, node_lib::Init)
 ^
hello.target.mk:95: recipe for target 'Release/obj.target/hello/hello.o' failed

Expected behavior

No errors like with nan version.

[gabrielschulhof]

NODE_API_MODULE prepends the string __napi_ to whatever function name you pass into it to create a new function that will be called when the module is loaded by Node.js.

Thus, if you pass in a function called FooInit, the macro will create a function named __napi_FooInit which ultimately results in Node.js calling FooInit.

OTOH, if you pass a namespaced function such as something::FooInit, the macro will unflinchingly prepend the prefix __napi_ to whatever it receives – in this case resulting in a function named __napi_something::FooInit. This is, of course, incorrect, since the namespace __napi_something doesn't exist.

That's why in the above error output the compiler complains that error: ‘__napi_node_lib’ has not been declared – because your namespace is node_lib, not __napi_node_lib.

I'll make a point to document this in node-gyp.md.