[nrf52] Precompile the core headers on the sdk-nrf build (#19826)

esphome/components/nrf52/__init__.py

@@ -8,6 +8,7 @@ import shutil
 import subprocess
 
 from esphome import pins
+from esphome.build_helpers import pch
 import esphome.codegen as cg
 from esphome.components.zephyr import (
     add_extra_script,
@@ -781,6 +782,67 @@ def process_stacktrace(config: ConfigType, line: str, backtrace_state: bool) ->
     return False
 
 
+# GCC only loads a precompiled header ahead of every other forced header, and
+# Zephyr forces two with -imacros. They hold macros only, so the C++ sources
+# of the app get them through the precompiled header.
+_PCH_CMAKE_LINES = [
+    "",
+    "# ESPHome precompiled header",
+    "get_property(esphome_options TARGET zephyr_interface",
+    "    PROPERTY INTERFACE_COMPILE_OPTIONS)",
+    "set(esphome_kept_options)",
+    "set(esphome_pch_headers)",
+    "foreach(option IN LISTS esphome_options)",
+    '  if(option MATCHES "imacros> (.+)$")',
+    '    list(APPEND esphome_pch_headers "${CMAKE_MATCH_1}")',
+    "    list(APPEND esphome_kept_options",
+    '        "$<$<NOT:$<AND:$<COMPILE_LANGUAGE:CXX>,$<STREQUAL:$<TARGET_PROPERTY:NAME>,app>>>:${option}>")',
+    "  else()",
+    '    list(APPEND esphome_kept_options "${option}")',
+    "  endif()",
+    "endforeach()",
+    "if(NOT esphome_pch_headers)",
+    '  message(FATAL_ERROR "ESPHome: the headers Zephyr forces were not found, so "',
+    '      "the precompiled header would not load (set ESPHOME_PCH_ENABLE=0)")',
+    "endif()",
+    "set_property(TARGET zephyr_interface",
+    '    PROPERTY INTERFACE_COMPILE_OPTIONS "${esphome_kept_options}")',
+    *(
+        f'list(APPEND esphome_pch_headers "${{CMAKE_CURRENT_LIST_DIR}}/../src/{header}")'
+        for header in pch.PCH_DEFAULT_HEADERS
+    ),
+    'list(TRANSFORM esphome_pch_headers REPLACE "(.+)" "$<$<COMPILE_LANGUAGE:CXX>:\\\\1>")',
+    "target_precompile_headers(app PRIVATE ${esphome_pch_headers})",
+]
+# Where CMake puts the .gch of the app, below its binary dir
+_PCH_SUM_PATH = "CMakeFiles/app.dir/cmake_pch.hxx.gch.sum"
+
+
+def _write_pch_checksum(build_dir: Path, source_dir: Path) -> None:
+    """Write the checksum ccache reads in place of the .gch. The app binary
+    dir only exists after the first configure; sysbuild nests it."""
+    app_dir = build_dir / "zephyr"
+    if not (app_dir / "CMakeCache.txt").is_file():
+        app_dir = build_dir
+    if not (app_dir / "CMakeCache.txt").is_file():
+        return
+    checksum = pch.pch_checksum(
+        CORE.relative_src_path(),
+        pch.PCH_DEFAULT_HEADERS,
+        (
+            str(CORE.data[KEY_CORE][KEY_FRAMEWORK_VERSION]),
+            zephyr_data()[KEY_BOARD],
+            # What the Zephyr configuration is generated from
+            *(
+                path.read_text(encoding="utf-8")
+                for path in sorted(source_dir.iterdir())
+                if path.suffix in (".conf", ".overlay")
+            ),
+        ),
+    )
+    write_file_if_changed(app_dir / _PCH_SUM_PATH, checksum + "\n")
+
+
 def _generate_cmake_lists() -> bool:
     """Write the project CMakeLists.txt, returning True if it changed."""
     compile_flags = get_project_compile_flags()
@@ -824,6 +886,9 @@ def _generate_cmake_lists() -> bool:
             ")",
         ]
 
+    if pch.pch_enabled():
+        lines += _PCH_CMAKE_LINES
+
     if link_flags:
         lines += [
             "",
@@ -897,6 +962,12 @@ def run_compile(args, config: ConfigType) -> bool:
         _LOGGER.info("Build inputs changed, cleaning %s", build_dir)
         rmtree(build_dir)
 
+    if pch.pch_enabled():
+        pch.log_pch_in_use()
+        # Zephyr turns ccache on by itself when it is installed
+        env.update(pch.ccache_pch_env())
+        _write_pch_checksum(build_dir, source_dir)
+
     west_cmd = _west_build_command(
         paths["python_executable"], board, build_dir, source_dir
     )

tests/unit_tests/components/nrf52/test_pch.py

@@ -0,0 +1,134 @@
+"""nrf52 sdk-nrf precompiled header: the CMake block and the ccache checksum."""
+
+from pathlib import Path
+from unittest.mock import Mock, patch
+
+import pytest
+
+from esphome.components import nrf52
+from esphome.components.zephyr.const import KEY_BOARD
+from esphome.const import KEY_CORE, KEY_FRAMEWORK_VERSION, Toolchain
+from esphome.core import CORE, EsphomeError
+
+SUM = "CMakeFiles/app.dir/cmake_pch.hxx.gch.sum"
+
+
+def _generate_cmake(tmp_path: Path) -> str:
+    CORE.config_path = tmp_path / "test.yaml"
+    CORE.build_path = tmp_path / "build"
+    CORE.name = "livingroom"
+    with (
+        patch(
+            "esphome.components.zephyr.library.generate_zephyr_modules",
+            return_value=[],
+        ),
+        patch.object(nrf52, "get_project_compile_flags", return_value=["-Os"]),
+        patch.object(nrf52, "get_project_link_flags", return_value=[]),
+    ):
+        nrf52._generate_cmake_lists()
+    return (tmp_path / "build" / "zephyr" / "CMakeLists.txt").read_text()
+
+
+def test_cmake_lists_precompile_the_core_headers(tmp_path: Path) -> None:
+    text = _generate_cmake(tmp_path)
+    assert "target_precompile_headers(app PRIVATE ${esphome_pch_headers})" in text
+    assert "/../src/esphome/core/pch_prefix.h" in text
+    # The headers Zephyr forces leave the C++ compiles of the app only
+    assert (
+        "$<$<NOT:$<AND:$<COMPILE_LANGUAGE:CXX>,"
+        "$<STREQUAL:$<TARGET_PROPERTY:NAME>,app>>>:${option}>"
+    ) in text
+    assert r'REPLACE "(.+)" "$<$<COMPILE_LANGUAGE:CXX>:\\1>"' in text
+    # A Zephyr that spells them another way must not go unnoticed
+    assert "if(NOT esphome_pch_headers)\n  message(FATAL_ERROR" in text
+
+
+def test_cmake_lists_pch_block_disabled(
+    monkeypatch: pytest.MonkeyPatch, tmp_path: Path
+) -> None:
+    monkeypatch.setenv("ESPHOME_PCH_ENABLE", "0")
+    text = _generate_cmake(tmp_path)
+    assert "precompile" not in text
+    assert "zephyr_interface" not in text
+
+
+def _write_checksum(tmp_path: Path, app: str, conf: str = "CONFIG_X=y\n") -> Path:
+    """Write the checksum for a build dir whose app image sits in ``app``."""
+    CORE.build_path = tmp_path
+    header = tmp_path / "src" / "esphome" / "core" / "pch_prefix.h"
+    header.parent.mkdir(parents=True, exist_ok=True)
+    header.write_text("#define M 1\n")
+    source_dir = tmp_path / "zephyr"
+    source_dir.mkdir(exist_ok=True)
+    (source_dir / "prj.conf").write_text(conf)
+    (source_dir / "CMakeLists.txt").write_text("not part of the checksum\n")
+    build_dir = tmp_path / ".pioenvs" / "livingroom"
+    (build_dir / app).mkdir(parents=True, exist_ok=True)
+    (build_dir / app / "CMakeCache.txt").write_text("")
+    with (
+        patch.dict(CORE.data, {KEY_CORE: {KEY_FRAMEWORK_VERSION: "2.9.2"}}),
+        patch.object(nrf52, "zephyr_data", return_value={KEY_BOARD: "board"}),
+    ):
+        nrf52._write_pch_checksum(build_dir, source_dir)
+    return build_dir / app / SUM
+
+
+@pytest.mark.parametrize("app", ["zephyr", "."])
+def test_pch_checksum_is_written_next_to_the_gch(tmp_path: Path, app: str) -> None:
+    """Sysbuild nests the app image; without it the build dir is the app."""
+    sum_path = _write_checksum(tmp_path, app)
+    assert len(sum_path.read_text().strip()) == 64
+
+
+def test_pch_checksum_tracks_the_zephyr_configuration(tmp_path: Path) -> None:
+    first = _write_checksum(tmp_path, "zephyr").read_text()
+    assert _write_checksum(tmp_path, "zephyr", "CONFIG_X=n\n").read_text() != first
+
+
+def test_pch_checksum_waits_for_the_first_configure(tmp_path: Path) -> None:
+    CORE.build_path = tmp_path
+    build_dir = tmp_path / ".pioenvs" / "livingroom"
+    nrf52._write_pch_checksum(build_dir, tmp_path / "zephyr")
+    assert not build_dir.exists()
+
+
+@pytest.fixture
+def run_cmd(tmp_path: Path) -> Mock:
+    CORE.config_path = tmp_path / "test.yaml"
+    CORE.build_path = tmp_path / "build"
+    CORE.name = "livingroom"
+    CORE.toolchain = Toolchain.SDK_NRF
+    with (
+        patch.object(nrf52, "check_and_install"),
+        patch.object(nrf52, "_generate_cmake_lists", return_value=False),
+        patch.object(
+            nrf52,
+            "get_build_paths",
+            return_value={"python_executable": "python3", "framework_path": tmp_path},
+        ),
+        patch.object(nrf52, "get_build_env", return_value={}),
+        patch.object(nrf52, "zephyr_data", return_value={KEY_BOARD: "board"}),
+        patch.object(nrf52, "run_command_ok", return_value=False) as run,
+    ):
+        yield run
+
+
+def test_ccache_pch_settings_reach_west(run_cmd: Mock) -> None:
+    # clear=True also drops ambient CCACHE_* and ESPHOME_PCH_* overrides
+    with (
+        patch.dict("os.environ", {}, clear=True),
+        pytest.raises(EsphomeError, match="nRF52 native build failed"),
+    ):
+        nrf52.run_compile(None, {})
+    env = run_cmd.call_args.kwargs["env"]
+    assert env["CCACHE_PCH_EXTSUM"] == "true"
+    assert env["CCACHE_SLOPPINESS"] == "pch_defines,time_macros"
+
+
+def test_disabled_leaves_the_west_environment_alone(
+    run_cmd: Mock, monkeypatch: pytest.MonkeyPatch
+) -> None:
+    monkeypatch.setenv("ESPHOME_PCH_ENABLE", "0")
+    with pytest.raises(EsphomeError, match="nRF52 native build failed"):
+        nrf52.run_compile(None, {})
+    assert "CCACHE_PCH_EXTSUM" not in run_cmd.call_args.kwargs["env"]