Resolve HIL flag helper from project root in SCons context

scripts/nrf52_hil_irq_observer.py

@@ -80,10 +80,12 @@ def replace_port(build_env, node):
     return _private_copy(build_env, node, patched_port, "port.c")
 
 
-def observer_enabled(flags=(), cppdefines=()):
+def observer_enabled(flags=(), cppdefines=(), parser_path=None):
     # Reuse the repository's effective -D/-U parser, including split -D values.
+    if parser_path is None:
+        parser_path = Path(__file__).with_name("nrf52_flash_trim.py")
     spec = importlib.util.spec_from_file_location(
-        "mesh_nrf52_flash_trim_irq_flags", Path(__file__).with_name("nrf52_flash_trim.py"))
+        "mesh_nrf52_flash_trim_irq_flags", parser_path)
     parser = importlib.util.module_from_spec(spec)
     spec.loader.exec_module(parser)
     values = parser.flag_defines(flags, cppdefines)
@@ -97,7 +99,9 @@ def observer_enabled(flags=(), cppdefines=()):
 
 
 def install(build_env):
-    if not observer_enabled(build_env.get("BUILD_FLAGS", ()), build_env.get("CPPDEFINES", ())):
+    # SCons executes extra scripts without defining __file__.
+    parser_path = Path(build_env.subst("$PROJECT_DIR")) / "scripts/nrf52_flash_trim.py"
+    if not observer_enabled(build_env.get("BUILD_FLAGS", ()), build_env.get("CPPDEFINES", ()), parser_path):
         return
     if (build_env.PioPlatform().name != "nordicnrf52"
             or build_env.BoardConfig().get("build.mcu", "").lower() != "nrf52840"):

test/test_nrf52_hil_irq_binding.py

@@ -82,6 +82,8 @@ class BuildEnv(dict):
         self.middleware.append((callback, pattern))
 
     def subst(self, value):
+        if value == "$PROJECT_DIR":
+            return str(ROOT)
         assert value == "$BUILD_DIR"
         return str(self.build_dir)
 
@@ -90,6 +92,17 @@ class BuildEnv(dict):
 
 
 class Nrf52HilIrqBindingTest(unittest.TestCase):
+    def test_actual_scons_entry_without_file_uses_project_root(self):
+        source = (ROOT / "scripts/nrf52_hil_irq_observer.py").read_text(encoding="ascii")
+        with tempfile.TemporaryDirectory() as directory:
+            for flag, expected in (("0", 0), ("1", 2)):
+                env = BuildEnv(Path(directory), "-DMESH_HIL_IRQ_TIMING=" + flag)
+                scope = {}
+                scope["Import"] = lambda name: scope.update({name: env})
+                exec(compile(source, "nrf52_hil_irq_observer.py", "exec"), scope)
+                self.assertNotIn("__file__", scope)
+                self.assertEqual(len(env.middleware), expected)
+
     def test_startup_changes_only_six_vectors_and_preserves_all_real_aliases(self):
         patched = PATCH.patched_startup(STARTUP.replace("\n", "\r\n"))
         self.assertEqual(PATCH.patched_startup(patched), patched)