[zephyr][nrf52] Rebuild native build when config inputs change (#17318)

Co-authored-by: Jonathan Swoboda <154711427+swoboda1337@users.noreply.github.com>

esphome/components/nrf52/__init__.py

@@ -58,7 +58,7 @@ from esphome.framework_helpers import (
     get_project_link_flags,
     run_command_ok,
 )
-from esphome.helpers import write_file_if_changed
+from esphome.helpers import rmtree, write_file_if_changed
 from esphome.storage_json import StorageJSON
 from esphome.types import ConfigType
 
@@ -697,7 +697,8 @@ def process_stacktrace(config: ConfigType, line: str, backtrace_state: bool) ->
     return False
 
 
-def _generate_cmake_lists() -> None:
+def _generate_cmake_lists() -> bool:
+    """Write the project CMakeLists.txt, returning True if it changed."""
     compile_flags = get_project_compile_flags()
     link_flags = get_project_link_flags()
 
@@ -732,7 +733,7 @@ def _generate_cmake_lists() -> None:
             ")",
         ]
 
-    write_file_if_changed(
+    return write_file_if_changed(
         CORE.relative_build_path("zephyr", "CMakeLists.txt"),
         "\n".join(lines) + "\n",
     )
@@ -751,12 +752,23 @@ def run_compile(args, config: ConfigType) -> bool:
     paths = get_build_paths()
     env = get_build_env()
 
-    _generate_cmake_lists()
+    cmake_lists_changed = _generate_cmake_lists()
 
     board = zephyr_data()[KEY_BOARD]
     build_dir = CORE.relative_pioenvs_path(CORE.name)
     source_dir = CORE.relative_build_path("zephyr")
 
+    # A missing CMake cache (dropped by zephyr's copy_files() on config
+    # change) or a changed CMakeLists.txt requires a pristine build: Zephyr
+    # caches Kconfig/devicetree state that survives a plain cmake re-run.
+    # West can't do the wipe — its pristine modes only recognize a build dir
+    # by reading ZEPHYR_BASE from the very cache that was dropped.
+    if (
+        cmake_lists_changed or not (build_dir / "CMakeCache.txt").is_file()
+    ) and build_dir.is_dir():
+        _LOGGER.info("Build inputs changed, cleaning %s", build_dir)
+        rmtree(build_dir)
+
     west_cmd = [
         str(paths["python_executable"]),
         "-m",

esphome/components/zephyr/__init__.py

@@ -8,6 +8,7 @@ from esphome.const import CONF_BOARD, KEY_CORE, KEY_FRAMEWORK_VERSION
 from esphome.core import CORE, CoroPriority, coroutine_with_priority
 from esphome.helpers import copy_file_if_changed, write_file_if_changed
 from esphome.types import ConfigType
+from esphome.writer import clean_cmake_cache
 
 from .const import (
     CONF_CDC_ACM,
@@ -203,7 +204,20 @@ def zephyr_add_user(key, value):
     user[key] += [value]
 
 
-def copy_files():
+def _write_file_if_changed_or_remove_when_empty(path: Path, content: str) -> bool:
+    """Write content to path, or remove a stale file when content is empty.
+
+    Returns True if the file changed on disk.
+    """
+    if content:
+        return write_file_if_changed(path, content)
+    if path.is_file():
+        path.unlink()
+        return True
+    return False
+
+
+def copy_files() -> None:
     user = zephyr_data()[KEY_USER]
     if user:
         entries = " ".join(
@@ -219,6 +233,8 @@ def copy_files():
             """
         )
 
+    changed = False
+
     for image, want_opts in zephyr_data()[KEY_PRJ_CONF].items():
         prj_conf = (
             "\n".join(
@@ -233,26 +249,25 @@ def copy_files():
         else:
             path = CORE.relative_build_path("zephyr/prj.conf")
 
-        write_file_if_changed(CORE.relative_build_path(path), prj_conf)
+        changed |= write_file_if_changed(path, prj_conf)
 
     for image, content in zephyr_data()[KEY_OVERLAY].items():
         if image:
             path = CORE.relative_build_path(f"sysbuild/{image}.overlay")
         else:
             path = CORE.relative_build_path("zephyr/app.overlay")
-        write_file_if_changed(path, content)
+        changed |= write_file_if_changed(path, content)
 
     for filename, path in zephyr_data()[KEY_EXTRA_BUILD_FILES].items():
-        copy_file_if_changed(
+        changed |= copy_file_if_changed(
             path,
             CORE.relative_build_path(filename),
         )
 
     pm_static = "\n".join(str(item) for item in zephyr_data()[KEY_PM_STATIC])
-    if pm_static:
-        write_file_if_changed(
-            CORE.relative_build_path("zephyr/pm_static.yml"), pm_static
-        )
+    changed |= _write_file_if_changed_or_remove_when_empty(
+        CORE.relative_build_path("zephyr/pm_static.yml"), pm_static
+    )
 
     kconfig = zephyr_data()[KEY_KCONFIG]
     if kconfig:
@@ -267,4 +282,12 @@ def copy_files():
             + "\n"
             + kconfig
         )
-        write_file_if_changed(CORE.relative_build_path("zephyr/Kconfig"), kconfig)
+    changed |= _write_file_if_changed_or_remove_when_empty(
+        CORE.relative_build_path("zephyr/Kconfig"), kconfig
+    )
+
+    if changed:
+        # A configure-time input changed; drop the CMake cache so the build
+        # can't reuse stale configure results (the native sdk-nrf toolchain
+        # rebuilds pristine when the cache is missing).
+        clean_cmake_cache()