✨ Suppress modules in Rich tracebacks with pretty_exceptions_suppress

[harkabeeparolus]

It would be useful to provide our users with the Rich traceback suppress parameter. This would allow developers to suppress uninteresting stack frames in tracebacks from other Python frameworks.

For example, python-github, which gives a verbose traceback with many frames on a simple GitlabAuthenticationError. I would like to be able to suppress this entire call stack, but it doesn't work:

#! /usr/bin/env -S uv run --script

# /// script
# dependencies = [ "python-gitlab", "typer", "rich" ]
# ///

import gitlab
import rich.traceback
import typer

# This code does nothing; Typer will override it
rich.traceback.install(suppress=[gitlab])

def main():
    gl = gitlab.Gitlab()
    print(gl.pagesdomains.list())

typer.run(main)

But with this pull request, you can suppress modules directly with Typer():

#! /usr/bin/env -S uv run --script

# /// script
# dependencies = [ "python-gitlab", "typer" ]
# ///

import gitlab
import typer

app = typer.Typer(pretty_exceptions_suppress=[gitlab])

@app.command()
def main():
    gl = gitlab.Gitlab()
    print(gl.pagesdomains.list())

app()

[github-actions]

📝 Docs preview

Last commit a2f39df at: https://bbb0094b.typertiangolo.pages.dev

Modified Pages

• https://bbb0094b.typertiangolo.pages.dev/tutorial/exceptions/ - (before)

[svlandeg]

Thanks @harkabeeparolus! I'll try to review this week or the next 🙏

[svlandeg]

Thanks for the PR!

I think the feature request in itself might make sense, though I'd have to double check with Tiangolo whether he'd want this or not.

Unfortunately the implementation in this PR is not good enough, as it uses a mock-up lib that users won't have in their env, and the test is not actually functional.

[svlandeg]

As we'll be vendoring Click in the near future, I suggest to not include the reference here.

Suggested change

	If you are developing with Python frameworks other than **Typer** and **Click**,
	If you are developing with other Python frameworks besides **Typer**,

[svlandeg]

I see that you're mocking the installation of gitlab for this to run in the test suite.

What I dislike about using gitlab as an example here, is that users reading the tutorial would have to install the lib just to replicate this one example.

Is there a different example, with already installed libraries, you can think of to showcase this functionality?

[svlandeg]

Similar to the other sections in this part of the tutorial, this section should show the output before and after setting this new var.

[svlandeg]

In general we tend to avoid comments in the source files, as they are displayed verbatim in the tutorial, which should have all the relevant information.

Suggested change

	# This will raise an exception if not authenticated:
	# GitlabAuthenticationError: 401: 401 Unauthorized
	# But the traceback will not show any lines from the gitlab module!

[svlandeg]

There's no need for noqa: E402 here, just move the import to the top of the file.

[svlandeg]

I'm afraid I disagree - this test doesn't actually test anything. What should get tested, is whether or not the traceback is suppressed. Switching to an actual lib that is in the environment (instead of doing all this mocking) would probably resolve that.

[harkabeeparolus]

Thank you for the review! @svlandeg ☺️

I see your point about not testing the actual suppression of traceback content. I thought that since this is a standard Rich feature, we'd effectively be testing whether internal Rich features are working or not. And I thought that would be Rich's responsibility.

However, since Typer de facto breaks this standard Rich feature (by overriding it), it would make sense to test what actually happens to the end user. Fair enough. 😊

I'll try to Google or brainstorm some kind of scenario with a long traceback stack through the Python standard library, I guess. 🤔

[harkabeeparolus]

I think I found a good use case, with only Python standard library modules. With an unknown URL protocol you get five (!) stack frames from urllib.request. 😳

Try this one with and without my PR, to really see how much mess the default Rich traceback formatter normally can remove in these scenarios:

import urllib.request

import typer

app = typer.Typer(pretty_exceptions_suppress=[urllib.request])


@app.command()
def main():
    urllib.request.urlopen("unknown://example.com")


app()

I'll look into updating my PR with this scenario instead of python-gitlab in the next few days, so we can actually test the business logic. And add a before-and-after that could be used to frighten small children. 😱 I think it'll be an improvement. ☺️

[svlandeg]

Sounds great!