Confusion with src and running in different directories

[joecox]

When I run Ruff with the isort rule from different directories, I get different results. I could use some help if I am misunderstanding or have misconfigured something.

Minimal reproducible example: https://github.com/joecox/ruff-rel-example.
ruff: 0.9.2

In a nutshell, with the structure:

.
└── backend
    ├── a.py
    ├── b.py
    ├── pyproject.toml
    └── uv.lock

With pyproject.toml:

[project]
...
dependencies = [
    "requests>=2.32.3",
]

[tool.ruff]
src = [
    ".",
]
[tool.ruff.lint]
select = ["I"]

And a.py importing one third-party import, and one first-party import:

from requests import get

from b import foo

Running Ruff from backend produces no errors:

$ cd backend && uvx --from "ruff==0.9.2" ruff check .
All checks passed!

But running Ruff from the root folder does not recognize the first-party import as such:

$ uvx --from "ruff==0.9.2" ruff check --diff --config=backend/pyproject.toml .
--- backend/a.py
+++ backend/a.py
@@ -1,3 +1,2 @@
-from requests import get
-
 from b import foo
+from requests import get

Would fix 1 error.

[dhruvmanila]

Thank you for taking the time to create a minimal reproducible example repository, that helps in understanding the issue quickly.

The reason this is happening is because of the --config option which if provided will try to resolve the path using the current working directory and make the current working directory as the project root. This means that both b and requests are considered as third party as seen using the --verbose flag:

$ ruff check --no-cache --diff --config=backend/pyproject.toml -v .
[2025-01-17][10:43:33][ruff::resolve][DEBUG] Using user-specified configuration file at: backend/pyproject.toml
...
[2025-01-17][10:43:33][ruff_linter::rules::isort::categorize][DEBUG] Categorized 'requests' as Known(ThirdParty) (NoMatch)
[2025-01-17][10:43:33][ruff_linter::rules::isort::categorize][DEBUG] Categorized 'b' as Known(ThirdParty) (NoMatch)
[2025-01-17][10:43:33][ruff_linter::rules::isort::categorize][DEBUG] Categorized 'b' as Known(ThirdParty) (NoMatch)
[2025-01-17][10:43:33][ruff_linter::rules::isort::categorize][DEBUG] Categorized 'requests' as Known(ThirdParty) (NoMatch)

And, when you run ruff from the backend/ directory, it'll correctly categorize b as known first party import:

$ ruff check --no-cache --diff -v .
[2025-01-17][10:45:52][ruff::resolve][DEBUG] Using configuration file (via parent) at: /private/tmp/ruff-rel-example/backend/pyproject.toml
...
[2025-01-17][10:45:52][ruff_linter::rules::isort::categorize][DEBUG] Categorized 'requests' as Known(ThirdParty) (NoMatch)
[2025-01-17][10:45:52][ruff_linter::rules::isort::categorize][DEBUG] Categorized 'b' as Known(FirstParty) (SourceMatch("/private/tmp/ruff-rel-example/backend"))

Related: #10989 (specifically, from #10989 (comment))

Can you provide more details about your intended workflow? Why do you need to use the --config option?

[joecox]

I'm running outside of backend due to pre-commit. But I think this is answered/resolved.

Here's what I think happened:

1. I ran ruff check as part of pre-commit without specifying a folder, and saw unexpected changes.
2. I ran with -v, saw [DEBUG] Using Ruff default settings, and misinterpreted this as meaning my pyproject.toml wasn't being respected.
3. I applied --config without having seen or understood this key part of the docs: https://docs.astral.sh/ruff/configuration/#config-file-discovery

any relative paths in that configuration file (like exclude globs or src paths) are resolved relative to the current working directory.

Confirmed that the fix is as simple as:

uvx --from "ruff==0.9.2" ruff check backend

Thanks!