Fixes mdlavin#12: Work around Bluebird long stack traces chomping 'Ca…

…used by'

index.js

@@ -1,5 +1,18 @@
 var inherits = require('inherits');
 
+function buildNestedCause (nested) {
+    var append = '\n';
+
+    // Bluebird long stack traces will drop any
+    // trace lines that don't match /^\s*at\s*/
+    // see https://github.com/mdlavin/nested-error-stacks/issues/12
+    if (process.env.BLUEBIRD_DEBUG || process.env.BLUEBIRD_LONG_STACK_TRACES) {
+        append += 'at ';
+    }
+    append += 'Caused By: ' + nested.stack;
+    return append;
+}
+
 var NestedError = function (message, nested) {
     this.nested = nested;
 
@@ -21,7 +34,7 @@ var NestedError = function (message, nested) {
             get: function () {
                 var stack = oldStackDescriptor.get.call(this);
                 if (this.nested) {
-                    stack += '\nCaused By: ' + this.nested.stack;
+                    stack += buildNestedCause(this.nested);
                 }
                 return stack;
             }

package.json

@@ -28,6 +28,7 @@
     "inherits": "~2.0.1"
   },
   "devDependencies": {
+    "bluebird": "^3.5.0",
     "chai": "~1.9.1",
     "mocha": "~1.18.2",
     "uuid": "~1.4.1"

test.js

@@ -86,4 +86,65 @@ describe('NestedErrors', function ()  {
         expect(messageDescriptor).to.be.undefined;
     });
 
+    context('Bluebird long stack trace support', function () {
+        var origEnv;
+
+        beforeEach(function () {
+            delete require.cache[require.resolve('bluebird')]
+            origEnv = process.env;
+        });
+
+        afterEach(function () {
+            process.env = origEnv;
+        });
+
+        it('without Bluebird long stack traces, includes child stack in \
+stacktrace without \'at\' prepended', function () {
+            var Promise = require('bluebird');
+
+            var childMessage = uuid.v1();
+            var child = new Error(childMessage);
+            var message = uuid.v1();
+            var nested = new NestedError(message, child);
+
+            return Promise.reject(child)
+                .catch(function (err) {
+                    expect(nested.stack).to.contain('Caused By: ' + child.stack);
+                    expect(nested.stack).to.not.contain('at Caused By: ' + child.stack);
+                });
+        });
+
+        it('with BLUEBIRD_DEBUG=1, includes child stack in stacktrace \
+with \'at\' prepended', function () {
+            process.env.BLUEBIRD_DEBUG=1;
+            var Promise = require('bluebird');
+
+            var childMessage = uuid.v1();
+            var child = new Error(childMessage);
+            var message = uuid.v1();
+            var nested = new NestedError(message, child);
+
+            return Promise.reject(child)
+                .catch(function (err) {
+                    expect(nested.stack).to.contain('at Caused By: ' + child.stack);
+                });
+        });
+
+        it('with BLUEBIRD_LONG_STACK_TRACES=1, includes child stack in \
+stacktrace with \'at\' prepended', function () {
+            process.env.BLUEBIRD_LONG_STACK_TRACES=1;
+            var Promise = require('bluebird');
+
+            var childMessage = uuid.v1();
+            var child = new Error(childMessage);
+            var message = uuid.v1();
+            var nested = new NestedError(message, child);
+
+            return Promise.reject(child)
+                .catch(function (err) {
+                    expect(nested.stack).to.contain('at Caused By: ' + child.stack);
+                });
+        });
+    });
+
 });