Add strict clang-format and clang-tidy, fix all findings

.clang-format

@@ -0,0 +1,24 @@
+---
+BasedOnStyle: LLVM
+Language: Cpp
+Standard: c++20
+ColumnLimit: 120
+IndentWidth: 2
+ContinuationIndentWidth: 4
+NamespaceIndentation: All
+AccessModifierOffset: -2
+PointerAlignment: Right
+QualifierAlignment: Left
+ReferenceAlignment: Right
+AllowShortFunctionsOnASingleLine: Inline
+AllowShortLambdasOnASingleLine: All
+AllowShortIfStatementsOnASingleLine: Never
+AllowShortLoopsOnASingleLine: false
+AlwaysBreakTemplateDeclarations: Yes
+BreakBeforeBraces: Attach
+InsertBraces: true
+IncludeBlocks: Preserve
+SortIncludes: CaseSensitive
+FixNamespaceComments: true
+SpaceAfterTemplateKeyword: true
+...

.clang-tidy

@@ -0,0 +1,48 @@
+---
+# Every disabled check has a reason; everything else is fixed, or NOLINT(check) with a reason where it can't be.
+Checks: >
+  -*,
+  bugprone-*,
+  cert-*,
+  clang-analyzer-*,
+  concurrency-*,
+  cppcoreguidelines-*,
+  misc-*,
+  modernize-*,
+  performance-*,
+  portability-*,
+  readability-*,
+  -modernize-use-trailing-return-type,
+  -misc-include-cleaner,
+  -misc-multiple-inheritance,
+  -cppcoreguidelines-owning-memory,
+  -cppcoreguidelines-pro-bounds-pointer-arithmetic,
+  -cppcoreguidelines-pro-bounds-constant-array-index,
+  -cppcoreguidelines-pro-bounds-avoid-unchecked-container-access,
+  -cppcoreguidelines-pro-type-static-cast-downcast
+
+# modernize-use-trailing-return-type: libwebrtc and pybind11 APIs, which we override and mirror, use leading returns
+# misc-include-cleaner: pybind11 and libwebrtc are used through umbrella headers the check maps to internal ones
+# misc-multiple-inheritance: libwebrtc observer interfaces (not pure virtual) are implemented next to our bases
+# cppcoreguidelines-owning-memory: libwebrtc takes raw `new` into its refcounting, and there's no GSL owner<>
+# cppcoreguidelines-pro-bounds-*: libwebrtc frames and audio are raw planes with strides, indexed per sample
+# cppcoreguidelines-pro-type-static-cast-downcast: libwebrtc has no RTTI, tracks are downcast by kind() as it does
+
+WarningsAsErrors: '*'
+HeaderFilterRegex: '.*/python-webrtc/cpp/src/.*'
+FormatStyle: file
+
+CheckOptions:
+  # running out of memory terminates anyway, and so does calling an empty std::function, a bug
+  bugprone-exception-escape.IgnoredExceptions: 'bad_alloc,bad_array_new_length,length_error,bad_function_call'
+  # pybind11 dataclass-like models (def_readwrite) are plain structs
+  misc-non-private-member-variables-in-classes.IgnoreClassesWithAllMemberVariablesBeingPublic: true
+  # `m` for the pybind11 module, `pc` for a peer connection, coordinates and iterators
+  readability-identifier-length.IgnoredVariableNames: '^(m|pc|id|it|x|y|u|v|uv|i|j)$'
+  readability-identifier-length.IgnoredParameterNames: '^(m|pc|id|it|x|y|u|v|uv|i|j)$'
+  readability-identifier-length.IgnoredLoopCounterNames: '^[ijkxy_]$'
+  # a width and a height, in the order everything takes them
+  bugprone-easily-swappable-parameters.IgnoredParameterNames: '"";iterator;Iterator;begin;Begin;end;End;first;First;last;Last;lhs;LHS;rhs;RHS;width;height'
+  cppcoreguidelines-special-member-functions.AllowSoleDefaultDtor: true
+  cppcoreguidelines-special-member-functions.AllowMissingMoveFunctionsWhenCopyIsDeleted: true
+...

.github/scripts/tidy.sh

@@ -0,0 +1,38 @@
+#!/usr/bin/env bash
+#
+# Runs clang-tidy (see .clang-tidy) over the extension sources, against a configured (not built) tree in build/tidy.
+#
+#   .github/scripts/tidy.sh [run-clang-tidy arguments, e.g. -fix or a file regex]
+#
+# The LLVM version is pinned to match clang-format in the Makefile.
+
+set -euo pipefail
+
+SRC="$(cd "$(dirname "${BASH_SOURCE[0]}")/../.." && pwd)"
+BUILD="${WRTC_TIDY_BUILD_DIR:-$SRC/build/tidy}"
+LLVM_VERSION=22.1.8
+
+if [ ! -x "$BUILD/venv/bin/python" ]; then
+    uv venv -q "$BUILD/venv" --python 3.13
+fi
+uv pip install -q --python "$BUILD/venv/bin/python" cmake ninja "pybind11>=3.0" "clang-tidy==$LLVM_VERSION"
+export PATH="$BUILD/venv/bin:$PATH"
+
+# libwebrtc for Linux is compiled against Chromium's libc++, which needs Clang
+if [ "$(uname)" = Linux ]; then
+    export CC="${CC:-clang}" CXX="${CXX:-clang++}"
+fi
+cmake -S "$SRC" -B "$BUILD" -G Ninja \
+    -DCMAKE_BUILD_TYPE=Debug \
+    -DPython_EXECUTABLE="$BUILD/venv/bin/python" \
+    -Dpybind11_DIR="$("$BUILD/venv/bin/python" -m pybind11 --cmakedir)" > /dev/null
+
+EXTRA=()
+if [ "$(uname)" = Darwin ]; then
+    # the wheel's clang doesn't know the SDK Apple Clang uses implicitly
+    EXTRA+=(-extra-arg=-isysroot"$(xcrun --show-sdk-path)")
+fi
+
+cd "$SRC"
+python "$BUILD/venv/bin/run-clang-tidy.py" -p "$BUILD" -quiet -j "$(getconf _NPROCESSORS_ONLN)" \
+    ${EXTRA[@]+"${EXTRA[@]}"} "$@" "$SRC/python-webrtc/cpp/src/"

.github/workflows/ci.yml

@@ -20,11 +20,20 @@ permissions:
 jobs:
   lint:
     runs-on: ubuntu-latest
+    env:
+      WRTC_CACHE_DIR: ${{ github.workspace }}/.wrtc-cache
     steps:
       - uses: actions/checkout@v7
       - uses: astral-sh/setup-uv@v7
       - run: uvx ruff check
       - run: uvx ruff format --check
+      - run: make format-check
+      # clang-tidy reads the libwebrtc headers, from the cache the wheels use
+      - uses: actions/cache@v6
+        with:
+          path: .wrtc-cache
+          key: libwebrtc-${{ runner.os }}-${{ runner.arch }}-${{ hashFiles('cmake/libwebrtc.cmake', 'cmake/libcxx/*.sha256') }}
+      - run: make tidy
 
   sdist:
     runs-on: ubuntu-latest

CMakeLists.txt

@@ -15,6 +15,8 @@ project(python_webrtc
 set(CMAKE_CXX_STANDARD 20)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 set(CMAKE_CXX_EXTENSIONS OFF)
+# for clang-tidy (make tidy) and editors
+set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
 if(MSVC)
   # libwebrtc is linked against the static release CRT
   set(CMAKE_MSVC_RUNTIME_LIBRARY MultiThreaded)

Makefile

@@ -1,4 +1,8 @@
-.PHONY: dev test asan tsan lint format stub wheels doc clean
+.PHONY: dev test asan tsan lint format format-check tidy stub wheels doc clean
+
+# pinned to the clang-tidy of .github/scripts/tidy.sh
+CLANG_FORMAT := uvx clang-format==22.1.8
+CPP_SRC = $(shell find python-webrtc/cpp/src -name '*.cpp' -o -name '*.h')
 
 # editable install; the extension is rebuilt automatically on import after C++ changes
 dev:
@@ -16,13 +20,21 @@ asan:
 tsan:
 	SANITIZE=thread .github/scripts/sanitizers-macos.sh $(O)
 
-lint:
+lint: format-check
 	uvx ruff check
 	uvx ruff format --check
 
 format:
 	uvx ruff check --fix
 	uvx ruff format
+	$(CLANG_FORMAT) -i $(CPP_SRC)
+
+format-check:
+	@$(CLANG_FORMAT) --dry-run --Werror $(CPP_SRC)
+
+# clang-tidy over the extension, see .clang-tidy
+tidy:
+	.github/scripts/tidy.sh $(O)
 
 stub:
 	uv run --no-sync pybind11-stubgen wrtc -o build/stubs