module: maintain separate cache for native modules

Fixes: nodejs#6160

lib/module.js

@@ -10,6 +10,7 @@ const fs = require('fs');
 const path = require('path');
 const internalModuleReadFile = process.binding('fs').internalModuleReadFile;
 const internalModuleStat = process.binding('fs').internalModuleStat;
+const internalModuleRealpath = process.binding('fs').internalModuleRealpath;
 
 const splitRe = process.platform === 'win32' ? /[\/\\]/ : /\//;
 const isIndexRe = /^index\.\w+?$/;
@@ -438,9 +439,20 @@ Module._extensions['.json'] = function(module, filename) {
 };
 
 
+const nativeModuleCache = {};
+
 //Native extension for .node
 Module._extensions['.node'] = function(module, filename) {
-  return process.dlopen(module, path._makeLong(filename));
+  const normalizedPath = internalModuleRealpath(path._makeLong(filename));
+  const cachedNativeModule = nativeModuleCache[normalizedPath];
+
+  if (cachedNativeModule) {
+    module.exports = cachedNativeModule;
+    return;
+  }
+
+  process.dlopen(module, path._makeLong(filename));
+  nativeModuleCache[normalizedPath] = module.exports;
 };
 
 

src/node_file.cc

@@ -581,6 +581,25 @@ static void InternalModuleStat(const FunctionCallbackInfo<Value>& args) {
   args.GetReturnValue().Set(rc);
 }
 
+static void InternalModuleRealpath(const FunctionCallbackInfo<Value>& args) {
+  Environment* env = Environment::GetCurrent(args);
+
+  CHECK(args[0]->IsString());
+  node::Utf8Value path(env->isolate(), args[0]);
+
+  uv_fs_t req;
+  int rc = uv_fs_realpath(env->event_loop(), &req, *path, nullptr);
+  if (rc == 0) {
+    const char* r = static_cast<const char*>(req.ptr);
+    Local<String> str = String::NewFromUtf8(env->isolate(),
+      r, v8::NewStringType::kNormal).ToLocalChecked();
+    args.GetReturnValue().Set(str);
+  } else {
+    args.GetReturnValue().Set(args[0]);
+  }
+  uv_fs_req_cleanup(&req);
+}
+
 static void Stat(const FunctionCallbackInfo<Value>& args) {
   Environment* env = Environment::GetCurrent(args);
 
@@ -1422,6 +1441,7 @@ void InitFs(Local<Object> target,
   env->SetMethod(target, "readdir", ReadDir);
   env->SetMethod(target, "internalModuleReadFile", InternalModuleReadFile);
   env->SetMethod(target, "internalModuleStat", InternalModuleStat);
+  env->SetMethod(target, "internalModuleRealpath", InternalModuleRealpath);
   env->SetMethod(target, "stat", Stat);
   env->SetMethod(target, "lstat", LStat);
   env->SetMethod(target, "fstat", FStat);

test/addons/clear-cache/binding.cc

@@ -0,0 +1,13 @@
+#include <node.h>
+#include <v8.h>
+
+void Method(const v8::FunctionCallbackInfo<v8::Value>& args) {
+  v8::Isolate* isolate = args.GetIsolate();
+  args.GetReturnValue().Set(v8::String::NewFromUtf8(isolate, "world"));
+}
+
+void init(v8::Local<v8::Object> target) {
+  NODE_SET_METHOD(target, "hello", Method);
+}
+
+NODE_MODULE(binding, init);

test/addons/clear-cache/binding.gyp

@@ -0,0 +1,8 @@
+{
+  'targets': [
+    {
+      'target_name': 'binding',
+      'sources': [ 'binding.cc' ]
+    }
+  ]
+}

test/addons/clear-cache/test.js

@@ -0,0 +1,13 @@
+'use strict';
+require('../../common');
+const assert = require('assert');
+
+function clearCache() {
+  Object.keys(require.cache).forEach((key) => delete require.cache[key]);
+}
+
+const val1 = require('./build/release/binding.node').hello;
+clearCache();
+const val2 = require('./build/release/binding.node').hello;
+
+assert(val1 == val2);