Fail unresolved unit renders with HTTP 500

site/doc/pages/unit_render.txt

@@ -18,6 +18,8 @@ Calls another UCE file and executes its `RENDER(Request& context)` function.
 
 If `context` is omitted, the current active request context is used.
 
+Calling a missing unit or render handler is a server error and sets HTTP status 500. If a unit is intentionally optional, inspect it with `unit_info()` before calling `unit_render()`.
+
 Examples:
 
 

site/tests/cli_runner.uce

@@ -329,6 +329,11 @@ void cli_run_site_suite(bool skip_local_service_pages = false)
 
 void cli_run_security_smoke()
 {
+	CliHttpResponse missing_unit = cli_frontend("/tests/unit_failure.uce");
+	cli_test_case("uce_unit_failure:unit_render missing target is HTTP 500",
+		missing_unit.status == 500 && cli_contains(missing_unit.body, "unit not found: does-not-exist.uce"),
+		"status=" + std::to_string(missing_unit.status) + " body=" + cli_truncate(missing_unit.body));
+
 	CliHttpResponse missing_component = cli_frontend("/tests/component_failure.uce");
 	cli_test_case("uce_component_failure:component_render missing target is HTTP 500",
 		missing_component.status == 500 && cli_contains(missing_component.body, "component not found: components/does-not-exist"),

site/tests/unit_failure.uce

@@ -0,0 +1,4 @@
+RENDER(Request& context)
+{
+	unit_render("does-not-exist.uce", context);
+}

src/wasm/core.cpp

@@ -727,6 +727,7 @@ void unit_render(String file_name, Request& request)
 	s32 slot = wasm_resolve_target(unit_name, handler, &resolved);
 	if(!slot)
 	{
+		request.set_status(500, "Internal Server Error");
 		print(component_error_banner("unit not found: " + trim(file_name)));
 		return;
 	}