Resolve the sysbuild app domain dir for the pch

esphome/components/nrf52/__init__.py

@@ -847,17 +847,35 @@ def _generate_cmake_lists() -> bool:
     )
 
 
-def _prepare_pch(build_dir: Path) -> None:
+def _app_build_dir(build_dir: Path) -> Path:
+    """The CMake binary dir of the application image.
+
+    Sysbuild (SDK >= 2.9.2) nests the app in a domain dir named after the
+    app source dir ("zephyr"); older SDKs configure it at the top level.
+    In the non-sysbuild layout build_dir/zephyr is the Zephyr output dir,
+    which has no CMakeCache.txt, so the probe cannot misfire."""
+    sysbuild_app = build_dir / "zephyr"
+    if (sysbuild_app / "CMakeCache.txt").is_file():
+        return sysbuild_app
+    return build_dir
+
+
+def _prepare_pch(app_dir: Path) -> None:
     """Build the .gch between the cmake and compile phases of west."""
     if not pch_enabled():
-        pch.discard_pch(build_dir)
+        pch.discard_pch(app_dir)
         pch.pch_disabled_degraded()
         return
-    autoconf = next(build_dir.glob("zephyr/include/generated/**/autoconf.h"), None)
+    # First, so OBJECT_DEPENDS is satisfied even when the pch degrades
+    app_dir.mkdir(parents=True, exist_ok=True)
+    write_file_if_changed(
+        app_dir / PCH_HEADER_NAME, pch_header_text(PCH_DEFAULT_HEADERS)
+    )
+    autoconf = next(app_dir.glob("zephyr/include/generated/**/autoconf.h"), None)
     if autoconf is None:
         # Fail closed: autoconf.h is the .sum's Kconfig identity
         _LOGGER.warning("No autoconf.h found; compiling without the pch")
-        pch.discard_pch(build_dir)
+        pch.discard_pch(app_dir)
         pch.pch_degraded("autoconf.h missing")
         return
     try:
@@ -866,11 +884,11 @@ def _prepare_pch(build_dir: Path) -> None:
         _LOGGER.warning(
             "Could not read %s; compiling without the pch: %s", autoconf, err
         )
-        pch.discard_pch(build_dir)
+        pch.discard_pch(app_dir)
         pch.pch_degraded(f"autoconf unreadable: {err}")
         return
     pch.prepare_pch(
-        build_dir,
+        app_dir,
         PCH_DEFAULT_HEADERS,
         (
             str(CORE.data[KEY_CORE][KEY_FRAMEWORK_VERSION]),
@@ -934,11 +952,6 @@ def run_compile(args, config: ConfigType) -> bool:
     ]
 
     if pch_enabled():
-        # Before the cmake phase: OBJECT_DEPENDS names the header
-        build_dir.mkdir(parents=True, exist_ok=True)
-        write_file_if_changed(
-            build_dir / PCH_HEADER_NAME, pch_header_text(PCH_DEFAULT_HEADERS)
-        )
         # Consumers carry the -include; gate the ccache relaxation on it
         # (Zephyr auto-enables ccache as the compiler launcher when found)
         mark_pch_emitted()
@@ -946,9 +959,13 @@ def run_compile(args, config: ConfigType) -> bool:
 
         # Split west into configure + build so the .gch is compiled from the
         # settled compile_commands.json flags between the two phases. Only
-        # when the DB is missing: any input change wipes the build dir, so
-        # an existing DB is settled, and --cmake-only always reconfigures
-        if not (build_dir / "compile_commands.json").is_file() and not run_command_ok(
+        # when the app DB is missing: any input change wipes the build dir,
+        # so an existing DB is settled, and --cmake-only reconfigures.
+        # Sysbuild configures the app image during its own configure, so the
+        # app's flags and autoconf.h are settled after this phase too.
+        if not (
+            _app_build_dir(build_dir) / "compile_commands.json"
+        ).is_file() and not run_command_ok(
             west_cmd + ["--cmake-only", "--", "-DCMAKE_EXPORT_COMPILE_COMMANDS=ON"],
             env=env,
             stream_output=True,
@@ -957,13 +974,14 @@ def run_compile(args, config: ConfigType) -> bool:
             raise EsphomeError("nRF52 native build failed")
 
     # An optional speedup must never abort the build
+    app_dir = _app_build_dir(build_dir)
     try:
-        _prepare_pch(build_dir)
+        _prepare_pch(app_dir)
     except Exception:  # noqa: BLE001  # pylint: disable=broad-exception-caught
         # Strict first: its own knob error must not mask the real failure
         strict = pch.pch_strict()
         # Raises itself if a stale .gch survives (silently wrong output)
-        pch.discard_pch(build_dir)
+        pch.discard_pch(app_dir)
         if strict:
             raise
         _LOGGER.warning(

tests/unit_tests/components/nrf52/test_pch.py

@@ -80,6 +80,26 @@ def test_prepare_pch_unreadable_autoconf_fails_closed(
     assert "Could not read" in caplog.text
 
 
+def test_app_build_dir_sysbuild_layout(build_dir: Path) -> None:
+    app = build_dir / "zephyr"
+    app.mkdir()
+    (app / "CMakeCache.txt").write_text("")
+    assert nrf52._app_build_dir(build_dir) == app
+
+
+def test_app_build_dir_top_level_layout(build_dir: Path) -> None:
+    # Non-sysbuild: build_dir/zephyr is the Zephyr output dir, no cache
+    (build_dir / "zephyr").mkdir()
+    assert nrf52._app_build_dir(build_dir) == build_dir
+
+
+def test_prepare_pch_writes_header_before_degrading(build_dir: Path) -> None:
+    # OBJECT_DEPENDS must be satisfied even when the pch degrades
+    with patch.object(nrf52.pch, "prepare_pch"):
+        nrf52._prepare_pch(build_dir)
+    assert (build_dir / "esphome_pch.h").is_file()
+
+
 def test_prepare_pch_extras_carry_build_identity(build_dir: Path) -> None:
     _write_autoconf(build_dir, "#define CONFIG_GPIO 1\n")
     with (
@@ -91,6 +111,7 @@ def test_prepare_pch_extras_carry_build_identity(build_dir: Path) -> None:
         patch.object(nrf52.pch, "prepare_pch") as prepare,
     ):
         nrf52._prepare_pch(build_dir)
+    assert (build_dir / "esphome_pch.h").is_file()
     (passed_dir, headers, extras) = prepare.call_args.args
     assert passed_dir == build_dir
     assert headers == nrf52.PCH_DEFAULT_HEADERS
@@ -174,13 +195,22 @@ class TestRunCompilePhases:
 
     def test_missing_db_runs_cmake_phase(self, compile_ctx) -> None:
         run_cmd, prepare, build_dir = compile_ctx
-        run_cmd.side_effect = [True, False]  # cmake-only ok, final build fails
+        results = iter([True, False])  # cmake-only ok, final build fails
+
+        def west(cmd, **kwargs):
+            # Phase 1 configures the sysbuild app domain
+            app = build_dir / "zephyr"
+            app.mkdir(parents=True, exist_ok=True)
+            (app / "CMakeCache.txt").write_text("")
+            return next(results)
+
+        run_cmd.side_effect = west
         with pytest.raises(EsphomeError, match="nRF52 native build failed"):
             self._run()
         assert "--cmake-only" in run_cmd.call_args_list[0].args[0]
         assert "--cmake-only" not in run_cmd.call_args_list[1].args[0]
-        assert prepare.called
-        assert (build_dir / "esphome_pch.h").is_file()
+        # The pch is prepared in the app domain dir, not the sysbuild root
+        assert prepare.call_args.args[0] == build_dir / "zephyr"
 
     def test_cmake_phase_failure_raises(self, compile_ctx) -> None:
         run_cmd, prepare, _ = compile_ctx
@@ -202,6 +232,20 @@ class TestRunCompilePhases:
         assert "--cmake-only" not in run_cmd.call_args.args[0]
         assert prepare.called
 
+    def test_settled_sysbuild_db_skips_cmake_phase(self, compile_ctx) -> None:
+        run_cmd, prepare, build_dir = compile_ctx
+        app = build_dir / "zephyr"
+        app.mkdir(parents=True)
+        (build_dir / "CMakeCache.txt").write_text("")
+        (app / "CMakeCache.txt").write_text("")
+        (app / "compile_commands.json").write_text("[]")
+        run_cmd.side_effect = [False]
+        with pytest.raises(EsphomeError, match="nRF52 native build failed"):
+            self._run()
+        assert run_cmd.call_count == 1
+        assert "--cmake-only" not in run_cmd.call_args.args[0]
+        assert prepare.call_args.args[0] == app
+
     def test_disabled_skips_header_and_cmake_phase(
         self, monkeypatch: pytest.MonkeyPatch, compile_ctx
     ) -> None: