Correctly handle exception from 'done'.

index.js

@@ -110,7 +110,9 @@
                 'return function(' + toList(args, 'done') + ') {\n' +
                 '    if(done) {\n' +
                 '        promiseFn.call(' + toList(params) + ').then(\n' +
-                '            function(result) {done(null, result);},\n' +
+                // Call `done()` inside `setTimeout()`, so that if `done` throws an error, it will
+                // be turned into an uncaught exception, instead of being swallowed by the Promise.
+                '            function(result) {setTimeout(function() {done(null, result);}, 0);},\n' +
                 '            function(err) {done(err);}\n' +
                 '        );\n' +
                 '        return null;\n' +
@@ -156,7 +158,14 @@
             }
 
             if(done) {
-                answer.then(function(result) {done(null, result);}, done);
+                answer.then(
+                    function(result) {
+                        // Call `done()` inside `setTimeout()`, so that if `done` throws an error, it will
+                        // be turned into an uncaught exception, instead of being swallowed by the Promise.
+                        setTimeout(function() {done(null, result);}, 0);
+                    },
+                    done
+                );
                 answer = null;
             }
 

test/addCallbackTest.js

@@ -1,11 +1,13 @@
 'use strict';
 
 const chai = require('chai');
-const pb = require('..');
 
 chai.use(require('chai-as-promised'));
 const {expect} = chai;
 
+const {expectUncaughtException} = require('./testUtils');
+const pb = require('..');
+
 describe('addCallback', () => {
     [
         {fn: Promise.resolve(7), comment: 'promise'},
@@ -27,8 +29,12 @@ describe('addCallback', () => {
         });
     });
 
+    const rejected = Promise.reject(new Error('boom'));
+    // This is here to stop Node from raising a "Potentially Unhandled Rejection Error".
+    rejected.catch(() => null);
+
     [
-        {fn: Promise.reject(new Error('boom')), comment: 'promise'},
+        {fn: rejected, comment: 'promise'},
         {fn: () => Promise.reject(new Error('boom')), comment: 'fn'},
         {fn: () => {throw new Error('boom');}, comment: 'throw'}
     ].forEach(({fn, comment}) => {
@@ -57,4 +63,17 @@ describe('addCallback', () => {
             () => pb.addCallback(null, {})
         ).to.throw('addCallback() don\'t know what to do with object');
     });
+
+    it('should deal correctly with exception from `done`', () => {
+        const fn = (done=null) => pb.addCallback(done, Promise.resolve('hello'));
+        const done = () => {throw new Error('boom')};
+
+        // We're calling into `fn`, but `done` is throwing an exception after `fn` is complete.  In
+        // an all-callback based world, this would cause an uncaught exception.  There's no better way to
+        // handle this, so make sure we get an uncaught exception here.
+        return expectUncaughtException(
+            () => fn(done)
+        );
+
+    });
 });

test/test.js

@@ -5,6 +5,7 @@ const chai = require('chai');
 chai.use(require('chai-as-promised'));
 const {expect} = chai;
 
+const {expectUncaughtException} = require('./testUtils');
 const promiseBreaker = require('../index');
 
 const makeTestCases = function(testFn, fns) {
@@ -253,4 +254,16 @@ describe("Use custom promise", () => {
             expect(result).to.equal(3);
         });
     });
+
+    it('should deal correctly with exception from `done`', () => {
+        const fn = promiseBreaker.break(() => Promise.resolve('hello'));
+        const done = () => {throw new Error('boom')};
+
+        // We're calling into `fn`, but `done` is throwing an exception after `fn` is complete.  In
+        // an all-callback based world, this would cause an uncaught exception.  There's no better way to
+        // handle this, so make sure we get an uncaught exception here.
+        return expectUncaughtException(
+            () => fn(done)
+        );
+    });
 });

test/testUtils.js

@@ -0,0 +1,13 @@
+exports.expectUncaughtException = function(fn) {
+    // Remove mocha's uncaughtException handler.
+    const originalListeners = process.listeners('uncaughtException');
+    originalListeners.forEach(listener => process.removeListener('uncaughtException', listener));
+
+    return new Promise(resolve => {
+        process.once('uncaughtException', resolve);
+        fn();
+    })
+    .then(() => {
+        originalListeners.forEach(listener => process.on('uncaughtException', listener))
+    });
+}