chore(ci): pin ruff and add pre-commit hooks (PROF-15511) (#174)

* style: ruff-format python_safe_point_bias README

Fixes ruff format --check CI failure (extra blank line in code block).

* chore(ci): pin ruff 0.15.5 and add pre-commit hooks

Pin CI ruff to match pyproject.toml expectations and add a minimal
pre-commit config (ruff-format + ruff --fix) so local runs match CI.

* chore: add scripts/lint and scripts/format for local ruff checks

Mirror dd-trace-py's scripts/lint workflow without git hooks — works with Datadog global core.hooksPath. Matches the pinned CI ruff job.

* fix(ci): run ruff --fix before format for convergence

ruff check --fix can rewrite imports; formatting last avoids leaving
files unformatted after a single scripts/format or pre-commit run.

* chore(ci): single ruff pin via requirements-dev.txt

- Add requirements-dev.txt as the only ruff version pin
- CI and scripts reference it; local pre-commit hook runs scripts/lint
- Document Python lint setup in README

* refactor(scripts): share ruff setup in ruff-common.sh

Author: vlad-scherbich

.github/workflows/ci.yml

@@ -29,7 +29,7 @@ jobs:
         with:
           python-version: "3.11"
       - name: Install ruff
-        run: pip install --no-cache-dir ruff
+        run: pip install --no-cache-dir -r requirements-dev.txt
       - name: Run ruff format check
         run: ruff format --check .
       - name: Run ruff lint check

.pre-commit-config.yaml

@@ -0,0 +1,11 @@
+# Optional git hooks for Python scenario files (same checks as CI — see scripts/lint).
+# Setup: pip install -r requirements-dev.txt pre-commit && pre-commit install
+# On Datadog laptops with global core.hooksPath, use ./scripts/lint instead of pre-commit install.
+repos:
+  - repo: local
+    hooks:
+      - id: ruff
+        name: ruff (scripts/lint)
+        entry: scripts/lint
+        language: system
+        types: [python]

README.md

@@ -10,6 +10,28 @@ Checkout #profiling-library-pager to get notified of test failures.
 Install go >= 1.25.1: `brew install go`, `choco install go`, etc.
 Install docker.
 
+### Python lint (scenario workloads)
+
+CI and local checks use [Ruff](https://docs.astral.sh/ruff/). Install once:
+
+```sh
+pip install -r requirements-dev.txt
+```
+
+```sh
+./scripts/lint          # check (matches the ci.yml ruff job)
+./scripts/format        # auto-fix formatting and lint
+```
+
+Optional git hooks (skip on Datadog laptops that use global `core.hooksPath` — run `./scripts/lint` manually instead):
+
+```sh
+pip install pre-commit
+pre-commit install
+```
+
+Ruff version is pinned only in `requirements-dev.txt`.
+
 ### Running Tests
 
 ```sh

requirements-dev.txt

@@ -0,0 +1,2 @@
+# Python dev tools for repo-wide lint/format (ci.yml, scripts/lint, scripts/format, pre-commit).
+ruff==0.15.5

scenarios/python_safe_point_bias_3.11/README.md

@@ -10,6 +10,7 @@ Verifies that the Python profiler correctly attributes CPU time to `slow_method`
 def empty_method() -> None:
     pass
 
+
 def slow_method() -> None:
     while time() < end_time:
         x = "h" + "e" + "l" + "l" + "o" + ","

scripts/format

@@ -0,0 +1,9 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+source "$(dirname "${BASH_SOURCE[0]}")/ruff-common.sh"
+ruff_common_setup
+ruff_resolve_targets "$@"
+
+ruff check --fix "${RUFF_TARGETS[@]}"
+ruff format "${RUFF_TARGETS[@]}"

scripts/lint

@@ -0,0 +1,10 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+# Matches the ruff job in .github/workflows/ci.yml (see also scripts/format).
+source "$(dirname "${BASH_SOURCE[0]}")/ruff-common.sh"
+ruff_common_setup
+ruff_resolve_targets "$@"
+
+ruff format --check "${RUFF_TARGETS[@]}"
+ruff check "${RUFF_TARGETS[@]}"

scripts/ruff-common.sh

@@ -0,0 +1,17 @@
+# Shared setup for scripts/lint and scripts/format.
+ruff_common_setup() {
+  RUFF_ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+  cd "$RUFF_ROOT"
+
+  if ! command -v ruff >/dev/null 2>&1; then
+    echo "ruff not found; install with: pip install -r $RUFF_ROOT/requirements-dev.txt" >&2
+    exit 1
+  fi
+}
+
+ruff_resolve_targets() {
+  RUFF_TARGETS=("$@")
+  if [ "${#RUFF_TARGETS[@]}" -eq 0 ]; then
+    RUFF_TARGETS=(".")
+  fi
+}