test-unit-serialize: add a very basic test that command deserialization works

We should test both serialization and deserialization works properly.
But the serialization/deserialization code is deeply entwined with the
manager state, and I think quite a bit of refactoring will be required before
this is possible. But let's at least add this simple test for now.

src/core/service.c

@@ -2725,7 +2725,7 @@ static int service_serialize(Unit *u, FILE *f, FDSet *fds) {
         return 0;
 }
 
-static int service_deserialize_exec_command(
+int service_deserialize_exec_command(
                 Unit *u,
                 const char *key,
                 const char *value) {

src/core/service.h

@@ -255,3 +255,6 @@ ServiceTimeoutFailureMode service_timeout_failure_mode_from_string(const char *s
 DEFINE_CAST(SERVICE, Service);
 
 #define STATUS_TEXT_MAX (16U*1024U)
+
+/* Only exported for unit tests */
+int service_deserialize_exec_command(Unit *u, const char *key, const char *value);

src/test/meson.build

@@ -133,6 +133,17 @@ tests += [
 
         [['src/test/test-serialize.c']],
 
+        [['src/test/test-unit-serialize.c'],
+         [libcore,
+          libshared],
+         [threads,
+          librt,
+          libseccomp,
+          libselinux,
+          libmount,
+          libblkid],
+         core_includes],
+
         [['src/test/test-utf8.c']],
 
         [['src/test/test-dev-setup.c']],

src/test/test-unit-serialize.c

@@ -0,0 +1,68 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include "rm-rf.h"
+#include "service.h"
+#include "tests.h"
+
+#define EXEC_START_ABSOLUTE \
+        "ExecStart 0 /bin/sh \"sh\" \"-e\" \"-x\" \"-c\" \"systemctl --state=failed --no-legend --no-pager >/failed ; systemctl daemon-reload ; echo OK >/testok\""
+#define EXEC_START_RELATIVE \
+        "ExecStart 0 sh \"sh\" \"-e\" \"-x\" \"-c\" \"systemctl --state=failed --no-legend --no-pager >/failed ; systemctl daemon-reload ; echo OK >/testok\""
+
+static void test_deserialize_exec_command_one(Manager *m, const char *key, const char *line, int expected) {
+        _cleanup_(unit_freep) Unit *u = NULL;
+        int r;
+
+        assert_se(unit_new_for_name(m, sizeof(Service), "test.service", &u) >= 0);
+
+        r = service_deserialize_exec_command(u, key, line);
+        log_debug("[%s] → %d (expected: %d)", line, r, expected);
+        assert(r == expected);
+
+        /* Note that the command doesn't match any command in the empty list of commands in 's', so it is
+         * always rejected with "Current command vanished from the unit file", and we don't leak anything. */
+}
+
+static void test_deserialize_exec_command(void) {
+        _cleanup_(manager_freep) Manager *m = NULL;
+        int r;
+
+        log_info("/* %s */", __func__);
+
+        r = manager_new(UNIT_FILE_USER, MANAGER_TEST_RUN_MINIMAL, &m);
+        if (manager_errno_skip_test(r)) {
+                log_notice_errno(r, "Skipping test: manager_new: %m");
+                return;
+        }
+
+        assert_se(r >= 0);
+
+        test_deserialize_exec_command_one(m, "main-command", EXEC_START_ABSOLUTE, 0);
+        test_deserialize_exec_command_one(m, "main-command", EXEC_START_RELATIVE, 0);
+        test_deserialize_exec_command_one(m, "control-command", EXEC_START_ABSOLUTE, 0);
+        test_deserialize_exec_command_one(m, "control-command", EXEC_START_RELATIVE, 0);
+
+        test_deserialize_exec_command_one(m, "control-command", "ExecStart 0 /bin/sh \"sh\"", 0);
+        test_deserialize_exec_command_one(m, "control-command", "ExecStart 0 /no/command ", -EINVAL);
+        test_deserialize_exec_command_one(m, "control-command", "ExecStart 0 /bad/quote \"", -EINVAL);
+        test_deserialize_exec_command_one(m, "control-command", "ExecStart s /bad/id x y z", -EINVAL);
+        test_deserialize_exec_command_one(m, "control-command", "ExecStart 11", -EINVAL);
+        test_deserialize_exec_command_one(m, "control-command", "ExecWhat 11 /a/b c d e", -EINVAL);
+}
+
+int main(int argc, char *argv[]) {
+        _cleanup_(rm_rf_physical_and_freep) char *runtime_dir = NULL;
+        int r;
+
+        test_setup_logging(LOG_DEBUG);
+
+        r = enter_cgroup_subroot(NULL);
+        if (r == -ENOMEDIUM)
+                return log_tests_skipped("cgroupfs not available");
+
+        assert_se(runtime_dir = setup_fake_runtime_dir());
+
+        test_deserialize_exec_command();
+
+        return EXIT_SUCCESS;
+}