Allowing tracebacks to be surfaced through abort

Currently, anytime abort(...) is called, It raises a new
exception which then suppresses any existing tracebacks.
This causes error monitoring systems like NewRelic to
report back worthless surface-level tracebacks that have
nothing to do with the application.
This change allows for the exception type to change, but
keep the existing traceback (if one exists). This allows
for monitoring systems to see a real traceback that can
be correlated to logged information.

Change-Id: Ibe6eb37e25b74d1dcfca76dfc1f5bbce28d34e85

2 files changed, 34 insertions, 6 deletions

diff --git a/pecan/core.py b/pecan/core.py
index a6525ca..14b9ad3 100644
--- a/pecan/core.py
+++ b/pecan/core.py
@@ -8,6 +8,7 @@ from mimetypes import guess_type, add_type
 from os.path import splitext
 import logging
 import operator
+import sys
 import types
 
 import six
@@ -123,12 +124,24 @@ def abort(status_code=None, detail='', headers=None, comment=None, **kw):
     :param comment: A comment to include in the response.
     '''
 
-    raise exc.status_map[status_code](
-        detail=detail,
-        headers=headers,
-        comment=comment,
-        **kw
-    )
+    # If there is a traceback, we need to catch it for a re-raise
+    try:
+        _, _, traceback = sys.exc_info()
+        webob_exception = exc.status_map[status_code](
+            detail=detail,
+            headers=headers,
+            comment=comment,
+            **kw
+        )
+
+        if six.PY3:
+            raise webob_exception.with_traceback(traceback)
+        else:
+            # Using exec to avoid python 3 parsers from crashing
+            exec('raise webob_exception, None, traceback')
+    finally:
+        # Per the suggestion of the Python docs, delete the traceback object
+        del traceback
 
 
 def redirect(location=None, internal=False, code=None, headers={},
diff --git a/pecan/tests/test_base.py b/pecan/tests/test_base.py
index e6adf0e..785b522 100644
--- a/pecan/tests/test_base.py
+++ b/pecan/tests/test_base.py
@@ -3,6 +3,7 @@
 import sys
 import os
 import json
+import traceback
 import warnings
 
 import webob
@@ -1121,6 +1122,20 @@ class TestAbort(PecanTestCase):
         r = app.get('/', status=401)
         assert r.status_int == 401
 
+    def test_abort_keeps_traceback(self):
+        last_exc, last_traceback = None, None
+
+        try:
+            try:
+                raise Exception('Bottom Exception')
+            except:
+                abort(404)
+        except Exception:
+            last_exc, _, last_traceback = sys.exc_info()
+
+        assert last_exc is HTTPNotFound
+        assert 'Bottom Exception' in traceback.format_tb(last_traceback)[-1]
+
 
 class TestScriptName(PecanTestCase):