feat: add ruff linter & formatter (#22576)

* chore: add ruff linter with base config

* ci: add ruff pre-commit hook

* ci: add ruff github actions workflow

* ci: run ruff only on changed files

.github/workflows/ruff.yml

@@ -0,0 +1,49 @@
+name: Ruff
+
+on:
+  push:
+    branches:
+      - main
+      - dev
+    paths:
+      - 'backend/**'
+      - 'pyproject.toml'
+  pull_request:
+    branches:
+      - main
+      - dev
+    paths:
+      - 'backend/**'
+      - 'pyproject.toml'
+
+jobs:
+  ruff:
+    name: 'Lint & Format Backend'
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - name: Get changed Python files
+        id: changed
+        run: |
+          if [ "${{ github.event_name }}" = "pull_request" ]; then
+            BASE=${{ github.event.pull_request.base.sha }}
+          else
+            BASE=${{ github.event.before }}
+          fi
+          FILES=$(git diff --name-only --diff-filter=ACMR "$BASE" HEAD -- 'backend/**.py' | xargs)
+          echo "files=$FILES" >> "$GITHUB_OUTPUT"
+
+      - name: Ruff check
+        if: steps.changed.outputs.files != ''
+        uses: astral-sh/ruff-action@v3
+        with:
+          args: check ${{ steps.changed.outputs.files }}
+
+      - name: Ruff format
+        if: steps.changed.outputs.files != ''
+        uses: astral-sh/ruff-action@v3
+        with:
+          args: format --check ${{ steps.changed.outputs.files }}

.pre-commit-config.yaml

@@ -0,0 +1,8 @@
+repos:
+  - repo: https://github.com/astral-sh/ruff-pre-commit
+    rev: v0.15.5
+    hooks:
+      - id: ruff
+        args: [--fix, backend]
+      - id: ruff-format
+        args: [backend]

pyproject.toml

@@ -213,4 +213,31 @@ ignore-words-list = 'ans'
 [dependency-groups]
 dev = [
     "pytest-asyncio>=1.0.0",
+    "ruff>=0.15.5",
 ]
+
+[tool.ruff]
+line-length = 120
+
+[tool.ruff.format]
+quote-style = "single"
+docstring-code-format = false
+
+[tool.ruff.lint]
+select = [
+  "E",    # pycodestyle errors
+  "F",    # pyflakes
+  "W",    # pycodestyle warnings
+  "I",    # isort
+  "UP",   # pyupgrade
+  "C90",  # mccabe
+  "Q",    # flake8-quotes
+  "ICN",  # flake8-import-conventions
+]
+
+# Plugin configs:
+flake8-import-conventions.banned-from = [ "ast", "datetime" ]
+flake8-import-conventions.aliases = { datetime = "dt" }
+flake8-quotes.inline-quotes = "single"
+mccabe.max-complexity = 10
+pydocstyle.convention = "google"