[squash] hide internals better

lib/events.js

@@ -148,9 +148,6 @@ function enhanceStackTrace(err, own) {
   err.stack = err.stack + sep + ownStack.join('\n');
 }
 
-const kExpandStack = Symbol('kExpandStack');
-Object.defineProperty(EventEmitter, 'kExpandStack', { value: kExpandStack });
-
 EventEmitter.prototype.emit = function emit(type, ...args) {
   let doError = (type === 'error');
 
@@ -167,9 +164,13 @@ EventEmitter.prototype.emit = function emit(type, ...args) {
       er = args[0];
     if (er instanceof Error) {
       try {
+        const { kExpandStackSymbol } = require('internal/util');
         const capture = {};
         Error.captureStackTrace(capture, EventEmitter.prototype.emit);
-        er[kExpandStack] = enhanceStackTrace.bind(null, er, capture);
+        Object.defineProperty(er, kExpandStackSymbol, {
+          value: enhanceStackTrace.bind(null, er, capture),
+          configurable: true
+        });
       } catch (e) {}
 
       // Note: The comments on the `throw` lines are intentional, they show

lib/internal/bootstrap_node.js

@@ -459,9 +459,9 @@
           // nothing to be done about it at this point.
         }
         try {
-          const { kExpandStack } = NativeModule.require('events');
-          if (typeof er[kExpandStack] === 'function')
-            er[kExpandStack]();
+          const { kExpandStackSymbol } = NativeModule.require('internal/util');
+          if (typeof er[kExpandStackSymbol] === 'function')
+            er[kExpandStackSymbol]();
         } catch (er) {}
         return false;
       }

lib/internal/util.js

@@ -371,5 +371,6 @@ module.exports = {
 
   // Used by the buffer module to capture an internal reference to the
   // default isEncoding implementation, just in case userland overrides it.
-  kIsEncodingSymbol: Symbol('node.isEncoding')
+  kIsEncodingSymbol: Symbol('kIsEncodingSymbol'),
+  kExpandStackSymbol: Symbol('kExpandStackSymbol')
 };