ci: add github actions job testing clang-20, clang-tidy, and iwyu

Author: ryanofsky

.github/workflows/ci.yml

@@ -0,0 +1,23 @@
+name: CI
+
+on:
+  push:
+  pull_request:
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v4
+
+    - name: Install Nix
+      uses: cachix/install-nix-action@v31       # 2025-05-27, from https://github.com/cachix/install-nix-action/tags
+      with:
+        nix_path: nixpkgs=channel:nixos-25.05   # latest release
+
+    - name: Configure, build, test
+      run: |
+        nix-shell --pure --run "ci/scripts/configure.sh"
+        nix-shell --pure --run "ci/scripts/build.sh"
+        nix-shell --pure --run "ci/scripts/test.sh"

CMakeLists.txt

@@ -15,16 +15,32 @@ include("cmake/compat_find.cmake")
 find_package(CapnProto REQUIRED)
 find_package(Threads REQUIRED)
 
-option(Libmultiprocess_ENABLE_CLANG_TIDY "Run clang-tidy with the compiler." OFF)
-if(Libmultiprocess_ENABLE_CLANG_TIDY)
+set(MPGEN_EXECUTABLE "" CACHE FILEPATH "If specified, should be full path to an external mpgen binary to use rather than the one built internally.")
+
+option(MP_ENABLE_CLANG_TIDY "Run clang-tidy with the compiler." OFF)
+if(MP_ENABLE_CLANG_TIDY)
   find_program(CLANG_TIDY_EXECUTABLE NAMES clang-tidy)
   if(NOT CLANG_TIDY_EXECUTABLE)
-    message(FATAL_ERROR "Libmultiprocess_ENABLE_CLANG_TIDY is ON but clang-tidy is not found.")
+    message(FATAL_ERROR "MP_ENABLE_CLANG_TIDY is ON but clang-tidy is not found.")
   endif()
   set(CMAKE_CXX_CLANG_TIDY "${CLANG_TIDY_EXECUTABLE}")
+
+  # Workaround for nix from https://gitlab.kitware.com/cmake/cmake/-/issues/20912#note_793338
+  # Nix injects header paths via $NIX_CFLAGS_COMPILE; CMake tags these as
+  # CMAKE_CXX_IMPLICIT_INCLUDE_DIRECTORIES and omits them from the compile
+  # database, so clang-tidy, which ignores $NIX_CFLAGS_COMPILE, can't find capnp
+  # headers. Setting them as standard passes them to clang-tidy.
+  set(CMAKE_CXX_STANDARD_INCLUDE_DIRECTORIES ${CMAKE_CXX_IMPLICIT_INCLUDE_DIRECTORIES})
 endif()
 
-set(MPGEN_EXECUTABLE "" CACHE FILEPATH "If specified, should be full path to an external mpgen binary to use rather than the one built internally.")
+option(MP_ENABLE_IWYU "Run include-what-you-use with the compiler." OFF)
+if(MP_ENABLE_IWYU)
+  find_program(IWYU_EXECUTABLE NAMES include-what-you-use iwyu)
+  if(NOT IWYU_EXECUTABLE)
+    message(FATAL_ERROR "MP_ENABLE_IWYU is ON but include-what-you-use was not found.")
+  endif()
+  set(CMAKE_CXX_INCLUDE_WHAT_YOU_USE "${IWYU_EXECUTABLE};-Xiwyu;--error")
+endif()
 
 include("cmake/compat_config.cmake")
 include("cmake/pthread_checks.cmake")
@@ -51,6 +67,7 @@ configure_file(include/mp/config.h.in "${CMAKE_CURRENT_BINARY_DIR}/include/mp/co
 
 # Generated C++ Capn'Proto schema files
 capnp_generate_cpp(MP_PROXY_SRCS MP_PROXY_HDRS include/mp/proxy.capnp)
+set_source_files_properties("${MP_PROXY_SRCS}" PROPERTIES SKIP_LINTING TRUE)
 
 # util library
 add_library(mputil OBJECT src/mp/util.cpp)

ci/scripts/build.sh

@@ -0,0 +1,4 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+cmake --build build -t all tests mpexamples -- -k 0

ci/scripts/configure.sh

@@ -0,0 +1,10 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+cmake -B build -G Ninja \
+  -DCMAKE_BUILD_TYPE=Debug \
+  -DCMAKE_CXX_COMPILER=clang++ \
+  -DCMAKE_CXX_FLAGS="-Wall -Wextra -Wpedantic -Wthread-safety-analysis -Wno-unused-parameter" \
+  -DCMAKE_EXPORT_COMPILE_COMMANDS=ON \
+  -DMP_ENABLE_CLANG_TIDY=ON \
+  -DMP_ENABLE_IWYU=ON

ci/scripts/test.sh

@@ -0,0 +1,4 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+ctest --test-dir build --output-on-failure

cmake/TargetCapnpSources.cmake

@@ -81,6 +81,8 @@ function(target_capnp_sources target include_prefix)
       DEPENDS ${capnp_file}
       VERBATIM
     )
+    # Skip linting for capnp-generated files but keep it for mpgen-generated ones
+    set_source_files_properties(${capnp_file}.c++ PROPERTIES SKIP_LINTING TRUE)
     target_sources(${target} PRIVATE
       ${CMAKE_CURRENT_BINARY_DIR}/${capnp_file}.c++
       ${CMAKE_CURRENT_BINARY_DIR}/${capnp_file}.proxy-client.c++

shell.nix

@@ -0,0 +1,14 @@
+{ pkgs ? import <nixpkgs> {} }:
+
+pkgs.mkShell {
+  buildInputs = with pkgs; [
+    capnproto
+  ];
+  nativeBuildInputs = with pkgs; [
+    cmake
+    include-what-you-use
+    llvmPackages_20.clang
+    llvmPackages_20.clang-tools
+    ninja
+  ];
+}