Formatting and Linting - Aspect Build

This lesson uses Aspect’s rules_lint to give automatic formatting and linting using ruff, a fast Rust-based re-implementation of the black formatter and flake8. Change the application code to contain some formatting and linting issues:

Use a mix of single and double quotes, which the formatter can safely fix without asking.
Add an unused import, which the formatter can auto-fix. However, since imports can have side effects, this may be unsafe.
Make a mistaken formatting string, {scheme (missing the closing curly brace), which the linter points out but has to be fixed manually.

So the file should now look like this:

import requests
from mylib import say
import os

x = requests.get('{scheme://w3schools.com/python/demopage.htm'.format("https"))

say.stamped(x.text)

Formatting

Before running the formatter, add the code to git if you haven’t already. You only want to format files that are tracked by version control.

% git init

Now run the format task with the Aspect CLI:

aspect format

You can see the quotes are now consistently double-quotes in the file.

With the tools/bazel wrapper installed, your team can keep typing bazel format and Bazelisk routes it through the Aspect CLI. Without the CLI you can still run the underlying formatter target directly with bazel run //tools/format.

Linting

Run bazel lint app/... to lint all targets beneath the app folder.

The lint command is provided by the Aspect CLI. If your org doesn’t use it, you can simulate a similar workflow with a script you check in.

You should see a result like the following. It reports both lint errors introduced, and offers to fix one of them.

You could choose “Show Diff” in this interactive prompt if you’d like to preview the change which is about to be applied. Choose “Yes” or “All” to update the source file. The unused import os is now removed from the source file. The other lint error still appears if you run bazel lint app/... again.

The exit code from bazel lint is non-zero. This indicates that ruff has been configured to report these as errors, and would block your workflow if linting is run as a CI step for example. You can use the pyproject.toml file to configure ruff differently.

​Formatting

​Linting

Formatting

Linting