Merge pull request #255 from seemethere/add_more_verbose_debug_error_handling

Add more verbose debug error handling

sanic/exceptions.py

@@ -1,4 +1,5 @@
 from .response import text
+from .log import log
 from traceback import format_exc
 
 
@@ -56,18 +57,31 @@ class Handler:
         :return: Response object
         """
         handler = self.handlers.get(type(exception), self.default)
-        response = handler(request=request, exception=exception)
+        try:
+            response = handler(request=request, exception=exception)
+        except:
+            if self.sanic.debug:
+                response_message = (
+                    'Exception raised in exception handler "{}" '
+                    'for uri: "{}"\n{}').format(
+                        handler.__name__, request.url, format_exc())
+                log.error(response_message)
+                return text(response_message, 500)
+            else:
+                return text('An error occurred while handling an error', 500)
         return response
 
     def default(self, request, exception):
         if issubclass(type(exception), SanicException):
             return text(
-                "Error: {}".format(exception),
+                'Error: {}'.format(exception),
                 status=getattr(exception, 'status_code', 500))
         elif self.sanic.debug:
-            return text(
-                "Error: {}\nException: {}".format(
-                    exception, format_exc()), status=500)
+            response_message = (
+                'Exception occurred while handling uri: "{}"\n{}'.format(
+                    request.url, format_exc()))
+            log.error(response_message)
+            return text(response_message, status=500)
         else:
             return text(
-                "An error occurred while generating the request", status=500)
+                'An error occurred while generating the response', status=500)

tests/test_exceptions.py

@@ -1,51 +1,86 @@
+import pytest
+
 from sanic import Sanic
 from sanic.response import text
 from sanic.exceptions import InvalidUsage, ServerError, NotFound
 from sanic.utils import sanic_endpoint_test
 
-# ------------------------------------------------------------ #
-#  GET
-# ------------------------------------------------------------ #
 
-exception_app = Sanic('test_exceptions')
+class SanicExceptionTestException(Exception):
+    pass
 
 
-@exception_app.route('/')
-def handler(request):
-    return text('OK')
+@pytest.fixture(scope='module')
+def exception_app():
+    app = Sanic('test_exceptions')
+
+    @app.route('/')
+    def handler(request):
+        return text('OK')
+
+    @app.route('/error')
+    def handler_error(request):
+        raise ServerError("OK")
+
+    @app.route('/404')
+    def handler_404(request):
+        raise NotFound("OK")
+
+    @app.route('/invalid')
+    def handler_invalid(request):
+        raise InvalidUsage("OK")
+
+    @app.route('/divide_by_zero')
+    def handle_unhandled_exception(request):
+        1 / 0
+
+    @app.route('/error_in_error_handler_handler')
+    def custom_error_handler(request):
+        raise SanicExceptionTestException('Dummy message!')
+
+    @app.exception(SanicExceptionTestException)
+    def error_in_error_handler_handler(request, exception):
+        1 / 0
+
+    return app
 
 
-@exception_app.route('/error')
-def handler_error(request):
-    raise ServerError("OK")
-
-
-@exception_app.route('/404')
-def handler_404(request):
-    raise NotFound("OK")
-
-
-@exception_app.route('/invalid')
-def handler_invalid(request):
-    raise InvalidUsage("OK")
-
-
-def test_no_exception():
+def test_no_exception(exception_app):
+    """Test that a route works without an exception"""
     request, response = sanic_endpoint_test(exception_app)
     assert response.status == 200
     assert response.text == 'OK'
 
 
-def test_server_error_exception():
+def test_server_error_exception(exception_app):
+    """Test the built-in ServerError exception works"""
     request, response = sanic_endpoint_test(exception_app, uri='/error')
     assert response.status == 500
 
 
-def test_invalid_usage_exception():
+def test_invalid_usage_exception(exception_app):
+    """Test the built-in InvalidUsage exception works"""
     request, response = sanic_endpoint_test(exception_app, uri='/invalid')
     assert response.status == 400
 
 
-def test_not_found_exception():
+def test_not_found_exception(exception_app):
+    """Test the built-in NotFound exception works"""
     request, response = sanic_endpoint_test(exception_app, uri='/404')
     assert response.status == 404
+
+
+def test_handled_unhandled_exception(exception_app):
+    """Test that an exception not built into sanic is handled"""
+    request, response = sanic_endpoint_test(
+        exception_app, uri='/divide_by_zero')
+    assert response.status == 500
+    assert response.body == b'An error occurred while generating the response'
+
+
+def test_exception_in_exception_handler(exception_app):
+    """Test that an exception thrown in an error handler is handled"""
+    request, response = sanic_endpoint_test(
+        exception_app, uri='/error_in_error_handler_handler')
+    assert response.status == 500
+    assert response.body == b'An error occurred while handling an error'