domain: set .domain non-enumerable on resources

In particular, this comes into play in the node repl, which apparently
enables domains by default. Whenever any Promise gets inspected, a
`.domain` property is displayed, which is *very confusing*, especially
since it has some kind of WeakReference attached to it, which is not yet
a language feature.

This change will prevent it from showing up in casual inspection, but
will leave it available for use.

lib/domain.js

@@ -58,7 +58,12 @@ const asyncHook = createHook({
     if (process.domain !== null && process.domain !== undefined) {
       // If this operation is created while in a domain, let's mark it
       pairing.set(asyncId, process.domain[kWeak]);
-      resource.domain = process.domain;
+      Object.defineProperty(resource, 'domain', {
+        configurable: true,
+        enumerable: false,
+        value: process.domain,
+        writable: true
+      });
     }
   },
   before(asyncId) {
@@ -196,7 +201,12 @@ Domain.prototype._errorHandler = function(er) {
   var caught = false;
 
   if (!util.isPrimitive(er)) {
-    er.domain = this;
+    Object.defineProperty(er, 'domain', {
+      configurable: true,
+      enumerable: false,
+      value: this,
+      writable: true
+    });
     er.domainThrown = true;
   }
 
@@ -313,7 +323,12 @@ Domain.prototype.add = function(ee) {
     }
   }
 
-  ee.domain = this;
+  Object.defineProperty(ee, 'domain', {
+    configurable: true,
+    enumerable: false,
+    value: this,
+    writable: true
+  });
   this.members.push(ee);
 };
 
@@ -352,7 +367,12 @@ function intercepted(_this, self, cb, fnargs) {
     var er = fnargs[0];
     er.domainBound = cb;
     er.domainThrown = false;
-    er.domain = self;
+    Object.defineProperty(er, 'domain', {
+      configurable: true,
+      enumerable: false,
+      value: self,
+      writable: true
+    });
     self.emit('error', er);
     return;
   }
@@ -406,7 +426,12 @@ Domain.prototype.bind = function(cb) {
     return bound(this, self, cb, arguments);
   }
 
-  runBound.domain = this;
+  Object.defineProperty(runBound, 'domain', {
+    configurable: true,
+    enumerable: false,
+    value: this,
+    writable: true
+  });
 
   return runBound;
 };
@@ -416,7 +441,12 @@ EventEmitter.usingDomains = true;
 
 const eventInit = EventEmitter.init;
 EventEmitter.init = function() {
-  this.domain = null;
+  Object.defineProperty(this, 'domain', {
+    configurable: true,
+    enumerable: false,
+    value: null,
+    writable: true
+  });
   if (exports.active && !(this instanceof exports.Domain)) {
     this.domain = exports.active;
   }
@@ -445,7 +475,12 @@ EventEmitter.prototype.emit = function(...args) {
 
     if (typeof er === 'object') {
       er.domainEmitter = this;
-      er.domain = domain;
+      Object.defineProperty(er, 'domain', {
+        configurable: true,
+        enumerable: false,
+        value: domain,
+        writable: true
+      });
       er.domainThrown = false;
     }
 

test/parallel/test-domain-add-remove.js

@@ -4,13 +4,15 @@ require('../common');
 const assert = require('assert');
 const domain = require('domain');
 const EventEmitter = require('events');
+const isEnumerable = Function.call.bind(Object.prototype.propertyIsEnumerable);
 
 const d = new domain.Domain();
 const e = new EventEmitter();
 const e2 = new EventEmitter();
 
 d.add(e);
 assert.strictEqual(e.domain, d);
+assert.strictEqual(isEnumerable(e, 'domain'), false);
 
 // Adding the same event to a domain should not change the member count
 let previousMemberCount = d.members.length;
@@ -19,8 +21,10 @@ assert.strictEqual(previousMemberCount, d.members.length);
 
 d.add(e2);
 assert.strictEqual(e2.domain, d);
+assert.strictEqual(isEnumerable(e2, 'domain'), false);
 
 previousMemberCount = d.members.length;
 d.remove(e2);
 assert.notStrictEqual(e2.domain, d);
+assert.strictEqual(isEnumerable(e2, 'domain'), false);
 assert.strictEqual(previousMemberCount - 1, d.members.length);

test/parallel/test-domain-async-id-map-leak.js

@@ -6,6 +6,7 @@ const assert = require('assert');
 const async_hooks = require('async_hooks');
 const domain = require('domain');
 const EventEmitter = require('events');
+const isEnumerable = Function.call.bind(Object.prototype.propertyIsEnumerable);
 
 // This test makes sure that the (async id → domain) map which is part of the
 // domain module does not get in the way of garbage collection.
@@ -21,7 +22,9 @@ d.run(() => {
 
   emitter.linkToResource = resource;
   assert.strictEqual(emitter.domain, d);
+  assert.strictEqual(isEnumerable(emitter, 'domain'), false);
   assert.strictEqual(resource.domain, d);
+  assert.strictEqual(isEnumerable(resource, 'domain'), false);
 
   // This would otherwise be a circular chain now:
   // emitter → resource → async id ⇒ domain → emitter.

test/parallel/test-domain-implicit-binding.js

@@ -4,13 +4,15 @@ const common = require('../common');
 const assert = require('assert');
 const domain = require('domain');
 const fs = require('fs');
+const isEnumerable = Function.call.bind(Object.prototype.propertyIsEnumerable);
 
 {
   const d = new domain.Domain();
 
   d.on('error', common.mustCall((err) => {
     assert.strictEqual(err.message, 'foobar');
     assert.strictEqual(err.domain, d);
+    assert.strictEqual(isEnumerable(err, 'domain'), false);
     assert.strictEqual(err.domainEmitter, undefined);
     assert.strictEqual(err.domainBound, undefined);
     assert.strictEqual(err.domainThrown, true);

test/parallel/test-domain-timer.js

@@ -3,12 +3,14 @@
 const common = require('../common');
 const assert = require('assert');
 const domain = require('domain');
+const isEnumerable = Function.call.bind(Object.prototype.propertyIsEnumerable);
 
 const d = new domain.Domain();
 
 d.on('error', common.mustCall((err) => {
   assert.strictEqual(err.message, 'foobar');
   assert.strictEqual(err.domain, d);
+  assert.strictEqual(isEnumerable(err, 'domain'), false);
   assert.strictEqual(err.domainEmitter, undefined);
   assert.strictEqual(err.domainBound, undefined);
   assert.strictEqual(err.domainThrown, true);