Degrade on header-generation failure, surface probe and touch errors

esphome/build_helpers/pch.py

@@ -221,8 +221,11 @@ def guarded_prepare(build_dir: Path, prepare: Callable[[], None]) -> None:
             raise
         header = build_dir / PCH_HEADER_NAME
         if not header.exists():
-            with suppress(OSError):
+            try:
                 header.touch()
+            except OSError as err:
+                # The coming OBJECT_DEPENDS error would hide the real cause
+                _LOGGER.warning("Could not create the pch placeholder: %s", err)
         _LOGGER.warning(
             "Precompiled header setup failed; compiling without it", exc_info=True
         )

esphome/components/nrf52/__init__.py

@@ -6,6 +6,7 @@ import logging
 from pathlib import Path
 import re
 import shutil
+import stat
 import subprocess
 
 from esphome import pins
@@ -838,9 +839,12 @@ def _app_build_dir(build_dir: Path) -> Path:
     non-sysbuild zephyr/ output dir has no CMakeCache.txt) so it stays
     truthful mid-build, unlike an SDK-version check."""
     sysbuild_app = build_dir / "zephyr"
-    if (sysbuild_app / "CMakeCache.txt").is_file():
-        return sysbuild_app
-    return build_dir
+    try:
+        cache = (sysbuild_app / "CMakeCache.txt").stat()
+    except (FileNotFoundError, NotADirectoryError):
+        return build_dir
+    # Other stat errors propagate; is_file() would silently mislocate the pch
+    return sysbuild_app if stat.S_ISREG(cache.st_mode) else build_dir
 
 
 def _prepare_pch(app_dir: Path) -> None:
@@ -976,7 +980,12 @@ def run_compile(args, config: ConfigType) -> bool:
                 stream_output=True,
                 cwd=str(paths["framework_path"]),
             ):
-                raise EsphomeError("nRF52 Zephyr header generation failed")
+                # A pch-only prerequisite: degrade, let the real build report
+                _LOGGER.warning(
+                    "Zephyr header generation failed; compiling without the pch"
+                )
+                pch.discard_pch(app_dir)
+                pch.pch_degraded("zephyr_generated_headers failed")
     else:
         app_dir = _app_build_dir(build_dir)
 

tests/unit_tests/build_helpers/test_pch.py

@@ -249,6 +249,7 @@ def test_pch_cmake_consumer_substitutes_target_and_sources(
 def test_pch_cmake_consumer_strict_escalates(
     monkeypatch: pytest.MonkeyPatch,
 ) -> None:
+    monkeypatch.delenv("ESPHOME_PCH_ENABLE", raising=False)
     monkeypatch.setenv("ESPHOME_PCH_STRICT", "1")
     assert "-Werror=invalid-pch" in pch.pch_cmake_consumer("app", "${APP_SOURCES}")
 

tests/unit_tests/components/nrf52/test_pch.py

@@ -98,6 +98,20 @@ def test_app_build_dir_top_level_layout(build_dir: Path) -> None:
     assert nrf52._app_build_dir(build_dir) == build_dir
 
 
+def test_app_build_dir_ignores_cache_directory(build_dir: Path) -> None:
+    (build_dir / "zephyr" / "CMakeCache.txt").mkdir(parents=True)
+    assert nrf52._app_build_dir(build_dir) == build_dir
+
+
+def test_app_build_dir_propagates_stat_errors(build_dir: Path) -> None:
+    # is_file() would swallow this and mislocate the pch
+    with (
+        patch.object(Path, "stat", side_effect=PermissionError("denied")),
+        pytest.raises(PermissionError),
+    ):
+        nrf52._app_build_dir(build_dir)
+
+
 def test_prepare_pch_extras_carry_build_identity(build_dir: Path) -> None:
     _write_autoconf(build_dir)
     with (
@@ -203,10 +217,24 @@ class TestRunCompilePhases:
         # The pch is prepared in the app domain dir, not the sysbuild root
         assert prepare.call_args.args[0] == build_dir / "zephyr"
 
-    def test_generated_headers_failure_raises(self, compile_ctx) -> None:
+    def test_generated_headers_failure_degrades(
+        self, compile_ctx, caplog: pytest.LogCaptureFixture
+    ) -> None:
+        run_cmd, prepare, _ = compile_ctx
+        # headers target fails, the real build still runs (and fails here)
+        run_cmd.side_effect = [True, False, False]
+        with pytest.raises(EsphomeError, match="nRF52 native build failed"):
+            self._run()
+        assert "Zephyr header generation failed" in caplog.text
+        assert prepare.called
+
+    def test_generated_headers_failure_strict_raises(
+        self, monkeypatch: pytest.MonkeyPatch, compile_ctx
+    ) -> None:
+        monkeypatch.setenv("ESPHOME_PCH_STRICT", "1")
         run_cmd, prepare, _ = compile_ctx
         run_cmd.side_effect = [True, False]
-        with pytest.raises(EsphomeError, match="header generation failed"):
+        with pytest.raises(EsphomeError, match="ESPHOME_PCH_STRICT"):
             self._run()
         assert not prepare.called