Add option to disable injecting context into error

README.md

@@ -112,14 +112,18 @@ function requestHandler() {
 }
 ```
 
-## cls.createNamespace(name)
+## cls.createNamespace(name, [options])
 
 * return: {Namespace}
 
 Each application wanting to use continuation-local values should create its own
 namespace. Reading from (or, more significantly, writing to) namespaces that
 don't belong to you is a faux pas.
 
+By default the current context will be added to any thrown error running in a
+namespace. If you wish to disable this behavior, set `options.injectErrorContext`
+to `false` (defaults to `true`).
+
 ## cls.getNamespace(name)
 
 * return: {Namespace}

context.js

@@ -14,12 +14,13 @@ var ERROR_SYMBOL = 'error@context';
 // load polyfill if native support is unavailable
 if (!process.addAsyncListener) require('async-listener');
 
-function Namespace(name) {
-  this.name   = name;
+function Namespace(name, injectErrorContext) {
+  this.name               = name;
   // changed in 2.7: no default context
-  this.active = null;
-  this._set   = [];
-  this.id     = null;
+  this.active             = null;
+  this._set               = [];
+  this.id                 = null;
+  this.injectErrorContext = injectErrorContext;
 }
 
 Namespace.prototype.set = function (key, value) {
@@ -49,7 +50,7 @@ Namespace.prototype.run = function (fn) {
     return context;
   }
   catch (exception) {
-    if (exception) {
+    if (this.injectErrorContext && exception) {
       exception[ERROR_SYMBOL] = context;
     }
     throw exception;
@@ -76,7 +77,7 @@ Namespace.prototype.bind = function (fn, context) {
       return fn.apply(this, arguments);
     }
     catch (exception) {
-      if (exception) {
+      if (this.injectErrorContext && exception) {
         exception[ERROR_SYMBOL] = context;
       }
       throw exception;
@@ -160,10 +161,16 @@ function get(name) {
   return process.namespaces[name];
 }
 
-function create(name) {
+function create(name, options) {
   assert.ok(name, "namespace must be given a name!");
 
-  var namespace = new Namespace(name);
+  options = options || {};
+  // `== null` tests for `null` and `undefined`
+  if (options.injectErrorContext == null) {
+    options.injectErrorContext = true;
+  }
+
+  var namespace = new Namespace(name, options.injectErrorContext);
   namespace.id = process.addAsyncListener({
     create : function () { return namespace.active; },
     before : function (context, storage) { if (storage) namespace.enter(storage); },

test/error-handling.tap.js

@@ -82,6 +82,31 @@ test("synchronous throw checks if error exists", function (t) {
   cls.destroyNamespace('cls@synchronous-null-error');
 });
 
+test("synchronous throw doesn't attach context", function (t) {
+  t.plan(2);
+
+  var namespace = cls.createNamespace('cls@synchronous-not-attached', {
+    injectErrorContext: false
+  });
+
+  namespace.run(function () {
+    namespace.set('value', 'transaction clear');
+    try {
+      namespace.run(function () {
+        namespace.set('value', 'transaction set');
+        throw new Error('cls@synchronous explosion');
+      });
+    }
+    catch (e) {
+      t.notOk(namespace.fromException(e), "context was not attached to error");
+    }
+
+    t.equal(namespace.get('value'), 'transaction clear', "everything was reset");
+  });
+
+  cls.destroyNamespace('cls@synchronous-not-attached');
+});
+
 test("throw in process.nextTick attaches the context", function (t) {
   t.plan(3);
 

test/namespaces.tap.js

@@ -6,7 +6,7 @@ var test = tap.test;
 var context = require('../context.js');
 
 test("namespace management", function (t) {
-  t.plan(8);
+  t.plan(10);
 
   t.throws(function () { context.createNamespace(); }, "name is required");
 
@@ -26,4 +26,9 @@ test("namespace management", function (t) {
                  "destroying works");
 
   t.notOk(process.namespaces.another, "namespace has been removed");
+
+  t.ok(namespace.injectErrorContext, "defaults to injecting error context");
+
+  namespace = context.createNamespace('explictOption', { injectErrorContext: false });
+  t.notOk(namespace.injectErrorContext, "setting injectErrorContext works");
 });