[PATCH 03/14] Add ruff import checks to b4 CI

[Tamir Duberstein <tamird@gmail.com>]

Run ruff as part of the b4 CI check script and enable import sorting in
Ruff so import ordering regressions show up in the review UI.

Keep Ruff as a subprocess and document the related upstream API
limitation.

Signed-off-by: Tamir Duberstein <tamird@gmail.com>
---
 pyproject.toml             |  4 ++--
 src/liblore/__init__.py    |  1 -
 src/liblore/node.py        |  3 +--
 src/liblore/utils.py       |  3 +--
 tests/conftest.py          |  3 +--
 tests/test_auth_headers.py |  1 -
 tests/test_email_utils.py  |  1 -
 tests/test_formatting.py   |  3 +--
 tests/test_mbox.py         |  4 +---
 tests/test_node.py         |  1 -
 tools/b4-ci-check.py       | 21 +++++++++++++++++++++
 11 files changed, 28 insertions(+), 17 deletions(-)

diff --git a/pyproject.toml b/pyproject.toml
index 7c9e1da..38be519 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -57,5 +57,5 @@ strict = true
 module = "authheaders"
 ignore_missing_imports = true
 
-[tool.ruff]
-target-version = "py39"
+[tool.ruff.lint]
+extend-select = ["I"]
diff --git a/src/liblore/__init__.py b/src/liblore/__init__.py
index ff4314a..1ffaaeb 100644
--- a/src/liblore/__init__.py
+++ b/src/liblore/__init__.py
@@ -3,7 +3,6 @@
 """liblore — shared library for public-inbox / lore.kernel.org access."""
 import email.charset
 import email.policy
-
 from email.message import EmailMessage
 
 __version__ = '0.7.1'
diff --git a/src/liblore/node.py b/src/liblore/node.py
index 5fb6343..66da1d7 100644
--- a/src/liblore/node.py
+++ b/src/liblore/node.py
@@ -15,11 +15,10 @@ import time
 import types
 import urllib.parse
 from datetime import datetime, timezone
+from email.message import EmailMessage
 
 import requests
 
-from email.message import EmailMessage
-
 from liblore import LibloreError, RemoteError
 from liblore.utils import (
     get_strict_thread,
diff --git a/src/liblore/utils.py b/src/liblore/utils.py
index 8d485da..e8926c6 100644
--- a/src/liblore/utils.py
+++ b/src/liblore/utils.py
@@ -3,7 +3,6 @@
 """Message parsing, email utilities, threading, and mbox splitting."""
 from __future__ import annotations
 
-from collections.abc import Sequence
 import datetime
 import email.header
 import email.parser
@@ -14,7 +13,7 @@ import logging
 import re
 import textwrap
 import urllib.parse
-
+from collections.abc import Sequence
 from email.message import EmailMessage
 
 from liblore import emlpolicy
diff --git a/tests/conftest.py b/tests/conftest.py
index b84fc35..ec8ec80 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -4,12 +4,11 @@ from __future__ import annotations
 
 import email.utils
 import textwrap
+from email.message import EmailMessage
 from typing import Protocol
 
 import pytest
 
-from email.message import EmailMessage
-
 from liblore import emlpolicy
 
 
diff --git a/tests/test_auth_headers.py b/tests/test_auth_headers.py
index 9edf4cd..9097048 100644
--- a/tests/test_auth_headers.py
+++ b/tests/test_auth_headers.py
@@ -13,7 +13,6 @@ import pytest
 from liblore import LibloreError
 from liblore.node import LoreNode
 
-
 # =====================================================================
 # Import-time validation
 # =====================================================================
diff --git a/tests/test_email_utils.py b/tests/test_email_utils.py
index ad8775f..74216d4 100644
--- a/tests/test_email_utils.py
+++ b/tests/test_email_utils.py
@@ -16,7 +16,6 @@ from liblore.utils import (
 )
 
 
-
 class TestMsgGetSubject:
     def test_plain_subject(self, make_msg: MsgFactory) -> None:
         msg = make_msg(subject='Just a plain subject')
diff --git a/tests/test_formatting.py b/tests/test_formatting.py
index a13593e..cb3cf80 100644
--- a/tests/test_formatting.py
+++ b/tests/test_formatting.py
@@ -2,10 +2,9 @@
 """Tests for email formatting and thread minimization."""
 from __future__ import annotations
 
-import pytest
-
 from email.message import EmailMessage
 
+import pytest
 from conftest import MsgFactory
 
 from liblore.utils import (
diff --git a/tests/test_mbox.py b/tests/test_mbox.py
index 3815e3f..9bc2271 100644
--- a/tests/test_mbox.py
+++ b/tests/test_mbox.py
@@ -3,9 +3,9 @@
 from __future__ import annotations
 
 import textwrap
-
 from email.message import EmailMessage
 
+from liblore import emlpolicy
 from liblore.utils import (
     get_clean_msgid,
     get_preferred_duplicate,
@@ -15,8 +15,6 @@ from liblore.utils import (
     split_mbox_as_bytes,
 )
 
-from liblore import emlpolicy
-
 
 class TestSplitMbox:
     def test_splits_two_messages(self, sample_mbox: bytes) -> None:
diff --git a/tests/test_node.py b/tests/test_node.py
index c2e7bf3..54d76d8 100644
--- a/tests/test_node.py
+++ b/tests/test_node.py
@@ -14,7 +14,6 @@ import requests
 from liblore import RemoteError
 from liblore.node import LoreNode
 
-
 # =====================================================================
 # Session management
 # =====================================================================
diff --git a/tools/b4-ci-check.py b/tools/b4-ci-check.py
index a51e19e..1bc5de1 100644
--- a/tools/b4-ci-check.py
+++ b/tools/b4-ci-check.py
@@ -5,6 +5,7 @@ from __future__ import annotations
 
 import json
 import os
+import subprocess
 import sys
 from contextlib import redirect_stderr, redirect_stdout
 from dataclasses import dataclass
@@ -32,12 +33,32 @@ def run_pytest(args: list[str]) -> tuple[str, str, int]:
     return stdout_buffer.getvalue(), stderr_buffer.getvalue(), status
 
 
+def run_subprocess(tool: str) -> Callable[[list[str]], tuple[str, str, int]]:
+    def run(args: list[str]) -> tuple[str, str, int]:
+        proc = subprocess.run(
+            [tool, *args],
+            capture_output=True,
+            text=True,
+        )
+        return proc.stdout, proc.stderr, proc.returncode
+
+    return run
+
+
 def main() -> None:
     sys.stdin.buffer.read()
 
     repo_root = Path(__file__).resolve().parent.parent
     os.chdir(repo_root)
     checks = [
+        Check(
+            tool='ruff lint',
+            args=['check'],
+            pass_summary='ruff lint passed',
+            # Ruff is invoked as a subprocess due to API limitations:
+            # https://github.com/astral-sh/ruff/issues/659
+            run=run_subprocess('ruff'),
+        ),
         # Mypy can emit JSON via "--output json", but b4 only renders details
         # as plain text, so preserving the normal formatter is more readable.
         Check(

-- 
2.53.0