dnf5daemon-server: Run transaction test for offline transactions

A serialized offline transaction consists only of local packages
downloaded to the `<system state dir>/offline` location. Unfortunately,
PGP checks for these packages are disabled by default due to the
`localpkg_gpgcheck` option default value.
Instead of testing the serialized transaction, this patch performs an
RPM transaction test on the originally resolved transaction, which still
retains information about the repositories from which the packages were
downloaded.
This approach also saves time required for deserialization and resolving
the testing transaction.

This ports the fix from rpm-software-management#1672
to dnf5daemon.

dnf5daemon-server/session.cpp

@@ -308,13 +308,28 @@ void Session::download_transaction_packages() {
 }
 
 void Session::store_transaction_offline() {
+    // Download transaction packages
     const auto & installroot = base->get_config().get_installroot_option().get_value();
     const auto & dest_dir = installroot / libdnf5::offline::DEFAULT_DATADIR.relative_path() / "packages";
     std::filesystem::create_directories(dest_dir);
     base->get_config().get_destdir_option().set(dest_dir);
     download_transaction_packages();
     set_cancel_download(Session::CancelDownload::NOT_ALLOWED);
 
+    // Test the transaction
+    // TODO(mblaha): store transaction test/run problems in the session and add an API
+    // to retrieve it
+    base->get_config().get_tsflags_option().set(libdnf5::Option::Priority::RUNTIME, "test");
+    auto result = transaction->run();
+    if (result != libdnf5::base::Transaction::TransactionRunResult::SUCCESS) {
+        throw sdbus::Error(
+            dnfdaemon::ERROR_TRANSACTION,
+            fmt::format(
+                "offline rpm transaction test failed with code {}.",
+                static_cast<std::underlying_type_t<libdnf5::base::Transaction::TransactionRunResult>>(result)));
+    }
+
+    // Serialize the transaction
     const auto & offline_datadir = installroot / libdnf5::offline::DEFAULT_DATADIR.relative_path();
     std::filesystem::create_directories(offline_datadir);
 
@@ -330,34 +345,13 @@ void Session::store_transaction_offline() {
     state_data.set_status(libdnf5::offline::STATUS_DOWNLOAD_INCOMPLETE);
     state.write();
 
-    // First, serialize the transaction
     transaction->store_comps(comps_location);
 
     const auto transaction_json_path = offline_datadir / "transaction.json";
     libdnf5::utils::fs::File transaction_json_file{transaction_json_path, "w"};
     transaction_json_file.write(transaction->serialize(packages_in_trans_dir, comps_in_trans_dir));
     transaction_json_file.close();
 
-    // Then, test the serialized transaction
-    // TODO(mblaha): store transaction test/run problems in the session and add an API
-    // to retrieve it
-    const auto & test_goal = std::make_unique<libdnf5::Goal>(*base);
-    test_goal->add_serialized_transaction(transaction_json_path);
-    auto test_transaction = test_goal->resolve();
-    if (test_transaction.get_problems() != libdnf5::GoalProblem::NO_PROBLEM) {
-        throw sdbus::Error(dnfdaemon::ERROR_TRANSACTION, "failed to resolve serialized offline transaction.");
-    }
-    base->get_config().get_tsflags_option().set(libdnf5::Option::Priority::RUNTIME, "test");
-
-    auto result = test_transaction.run();
-    if (result != libdnf5::base::Transaction::TransactionRunResult::SUCCESS) {
-        throw sdbus::Error(
-            dnfdaemon::ERROR_TRANSACTION,
-            fmt::format(
-                "offline rpm transaction test failed with code {}.",
-                static_cast<std::underlying_type_t<libdnf5::base::Transaction::TransactionRunResult>>(result)));
-    }
-
     // Download and transaction test complete. Fill out entries in offline
     // transaction state file.
     state_data.set_cachedir(base->get_config().get_cachedir_option().get_value());