Enable the pch on esp32 via PlatformIO for CI speed

.github/workflows/ci-docker.yml

@@ -204,7 +204,7 @@ jobs:
           - host
         # Strict by default so a new matrix id cannot silently join in the
         # degrade-quietly mode the knob exists to catch; the knob is inert
-        # where no pch code runs (esp32-*-platformio, nrf52).
+        # where no pch code runs (nrf52).
         # Opt-outs: libretiny GCC rejects its own pch until a toolchain bump.
         include:
           - id: bk72xx-arduino

esphome/build_helpers/pch.py

@@ -64,6 +64,10 @@ PCH_ARTIFACT_NAMES = (
 # The core defines header every backend anchors its prefix on.
 PCH_CORE_HEADER = "esphome/core/defines.h"
 
+# Guarded curated-prefix wrapper for PlatformIO backends without framework
+# force-includes (host, esp32); folded by the pch script via build_src_flags.
+PCH_PREFIX_HEADER = "esphome/core/pch_prefix.h"
+
 # Prefix-header contents for backends that inject a curated set (rather
 # than mirroring the TUs' own force-includes), defines.h first so USE_*
 # macros exist for the rest. Deliberately hard-coded: frequency-derived

esphome/components/esp32/__init__.py

@@ -10,6 +10,7 @@ import subprocess
 from typing import Any
 
 from esphome import yaml_util
+from esphome.build_helpers.pch import PCH_PREFIX_HEADER, pch_enabled, pch_extra_scripts
 import esphome.codegen as cg
 from esphome.components.const import CONF_ENABLE_OTA_DOWNGRADE_PROTECTION
 from esphome.config_helpers import filter_source_files_from_defines
@@ -57,6 +58,7 @@ from esphome.coroutine import CoroPriority, coroutine_with_priority
 from esphome.espidf.component import generate_idf_components
 import esphome.final_validate as fv
 from esphome.helpers import copy_file_if_changed, rmtree, write_file_if_changed
+from esphome.platformio.toolchain import copy_pch_script
 from esphome.schema_extractors import SCHEMA_EXTRACT, schema_extractor
 from esphome.types import ConfigType
 from esphome.writer import clean_build, clean_cmake_cache
@@ -2433,6 +2435,11 @@ async def to_code(config):
 
         cg.add_platformio_option("lib_ldf_mode", "off")
         cg.add_platformio_option("lib_compat_mode", "strict")
+        # CI-speed only: this toolchain is being dropped, so the pch gets
+        # the same curated prefix as host with no further investment
+        cg.add_platformio_option("extra_scripts", pch_extra_scripts())
+        if pch_enabled():
+            cg.add_platformio_option("build_src_flags", f"-include {PCH_PREFIX_HEADER}")
         cg.add_platformio_option("platform", conf[CONF_PLATFORM_VERSION])
         cg.add_platformio_option("board", config[CONF_BOARD])
         cg.add_platformio_option("board_upload.flash_size", config[CONF_FLASH_SIZE])
@@ -3350,6 +3357,8 @@ def _write_idf_component_yml():
 def copy_files():
     _write_sdkconfig()
     _write_idf_component_yml()
+    if not CORE.using_toolchain_esp_idf:
+        copy_pch_script()
 
     if "partitions.csv" not in CORE.data[KEY_ESP32][KEY_EXTRA_BUILD_FILES]:
         flash_size = CORE.data[KEY_ESP32][KEY_FLASH_SIZE]

esphome/components/host/__init__.py

@@ -1,4 +1,4 @@
-from esphome.build_helpers.pch import pch_enabled, pch_extra_scripts
+from esphome.build_helpers.pch import PCH_PREFIX_HEADER, pch_enabled, pch_extra_scripts
 import esphome.codegen as cg
 import esphome.config_validation as cv
 from esphome.const import (
@@ -19,9 +19,6 @@ from .const import KEY_HOST
 # force import gpio to register pin schema
 from .gpio import host_pin_to_code  # noqa: F401
 
-# Guarded wrapper: build_src_flags reaches C/assembly edges too
-HOST_PCH_PREFIX = "esphome/core/pch_prefix.h"
-
 CODEOWNERS = ["@esphome/core", "@clydebarrow"]
 AUTO_LOAD = ["network", "preferences"]
 IS_TARGET_PLATFORM = True
@@ -67,7 +64,7 @@ async def to_code(config: ConfigType) -> None:
         # Gated so ESPHOME_PCH_ENABLE=0 restores the strict view. When the
         # .gch fails to build or load, the force-include stays and every TU
         # parses the closure as text: correct, but slower than no pch.
-        cg.add_platformio_option("build_src_flags", f"-include {HOST_PCH_PREFIX}")
+        cg.add_platformio_option("build_src_flags", f"-include {PCH_PREFIX_HEADER}")
 
 
 # Called by writer.py

tests/unit_tests/test_host_pch_prefix.py

@@ -1,16 +1,16 @@
-"""The host pch prefix must keep resolving; a rename would silently
+"""The pch prefix must keep resolving; a rename would silently
 collapse the precompiled set to defines.h with strict CI still green."""
 
 from pathlib import Path
 import re
 
-from esphome.components.host import HOST_PCH_PREFIX
+from esphome.build_helpers.pch import PCH_PREFIX_HEADER
 
 REPO = Path(__file__).parents[2]
 
 
 def test_host_pch_prefix_resolves() -> None:
-    prefix = REPO / HOST_PCH_PREFIX
+    prefix = REPO / PCH_PREFIX_HEADER
     assert prefix.is_file()
     body = prefix.read_text()
     includes = re.findall(r'#include "([^"]+)"', body)