ci: Introduce buildifier style check (#10)

.github/actions/setup/action.yml

@@ -0,0 +1,14 @@
+---
+name: Set up environment
+
+runs:
+  using: composite
+  steps:
+    - name: Install bazelisk
+      shell: bash
+      run: |
+        bazelisk_dir="$(realpath "$(mktemp -d -p .)")"
+        wget https://github.com/bazelbuild/bazelisk/releases/download/v1.19.0/bazelisk-linux-amd64 \
+          -O "${bazelisk_dir}/bazelisk"
+        chmod +x "${bazelisk_dir}/bazelisk"
+        echo "${bazelisk_dir}" >> "${GITHUB_PATH}"

.github/workflows/tests.yml

@@ -0,0 +1,42 @@
+---
+name: Run unit tests
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  unit-test:
+    runs-on: ubuntu-22.04
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+        with:
+          ref: ${{ github.head_ref }}
+      - name: Set up
+        uses: ./.github/actions/setup
+      - name: Run unit tests
+        run: ./execute_tests.bash
+
+  style-check:
+    runs-on: ubuntu-22.04
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+        with:
+          ref: ${{ github.head_ref }}
+      - name: Set up
+        uses: ./.github/actions/setup
+      - name: Run formatters and linters
+        run: ./style_check.bash
+      - name: Fail if some files are changed
+        run: |
+          if ! git diff --exit-code; then
+            echo "ERROR: Files are changed by formatters" >&2
+            exit 1
+          fi

MODULE.bazel

@@ -1,16 +1,20 @@
 """Module for `rules_build_error`.
 """
 
-module(name = "rules_build_error", version = "0.1.0")
+module(
+    name = "rules_build_error",
+    version = "0.1.0",
+)
 
 bazel_dep(name = "bazel_skylib", version = "1.5.0", dev_dependency = True)
-
 bazel_dep(name = "toolchains_llvm", version = "1.0.0", dev_dependency = True)
 
 llvm = use_extension("@toolchains_llvm//toolchain/extensions:llvm.bzl", "llvm")
 llvm.toolchain(
     llvm_version = "17.0.6",
 )
-
 use_repo(llvm, "llvm_toolchain")
+
 register_toolchains("@llvm_toolchain//:all")
+
+bazel_dep(name = "buildifier_prebuilt", version = "6.4.0", dev_dependency = True)

style_check.bash

@@ -0,0 +1,20 @@
+#!/usr/bin/env bash
+#
+# Code style checker (linter and formatter)
+
+set -euo pipefail
+
+# Bazel executable with some arguments
+BAZEL_EXECUTABLE=(
+    "env"
+    "-i"
+    BAZEL_DO_NOT_DETECT_CPP_TOOLCHAIN=1
+    BAZELISK_HOME=.cache/bazelisk
+    "HOME=${HOME}"
+    "PATH=${PATH}"
+    bazelisk
+)
+
+buildifier_targets="$(git ls-files *.bzl *.bazel BUILD WORKSPACE MODULE | xargs -I{} echo "$(pwd)/{}")"
+
+"${BAZEL_EXECUTABLE[@]}" run -- @buildifier_prebuilt//:buildifier -lint=fix ${buildifier_targets}