Falcon integration does not respect custom exception handlers

[alexmic]

How do you use Sentry?

Sentry Saas (sentry.io)

Version

1.5.6

Steps to Reproduce

1. Attach a custom exception handler:

import marshmallow

def marshmallow_validation_error_handler(req, res, exc, params):
    """Transforms a marshmallow validation error into the appropriate HTTP response."""
    raise falcon.HTTPError(400)

api.add_error_handler(marshmallow.ValidationError, marshmallow_validation_error_handler)

2. Do an API request that leads to a validation error

Expected Result

The marshmallow exception should not have been reported to Sentry.

Actual Result

The custom exception leads to a 4xx, not a 5xx, yet it is still reported as an unhandled error on Sentry.

[sl0thentr0py]

thx for reporting @alexmic, if you want it fixed sooner, PRs always welcome!

[khuongduy354]

I have a question,

In the docs, Sentry detect if Falcon is in dependencies, I've been looking for the code doing that but haven't found it yet.
At first, I guess the dependencies detection code is inside the init method

But after reading class Client and Hub, these just takes integration options parameters, and doesn't do dependencies scan.

Can you show me where that part is ?

[sentrivana]

Hey @khuongduy354, you're looking for the setup_integrations function which is called at client setup here:

sentry-python/sentry_sdk/client.py

Line 263 in 3176dde

self.integrations = setup_integrations(

These are the specific parts responsible for the detection:

sentry-python/sentry_sdk/integrations/__init__.py

Lines 38 to 45 in 3176dde

	for import_string in all_import_strings:
	try:
	module, cls = import_string.rsplit(".", 1)
	yield getattr(import_module(module), cls)
	except (DidNotEnable, SyntaxError) as e:
	logger.debug(
	"Did not import default integration %s: %s", import_string, e
	)

and

sentry-python/sentry_sdk/integrations/__init__.py

Line 140 in 3176dde

except DidNotEnable as e:

(An integration raises a special DidNotEnable exception if it fails to import the instrumented library and that tells this code that the library is not installed and the integration for it shouldn't be enabled.)

But please note that someone's already working on this issue.

[szokeasaurusrex]

We have fixed this issue for Falcon versions 3.0 and above only. In case anyone encounters this same bug in an older Falcon version, please feel free to submit a new issue, referencing this one.