PBCKP-553 fix a typo in merge preconditions check

Author: Sergey Fukanchik

src/merge.c

@@ -337,7 +337,7 @@ do_merge(InstanceState *instanceState, time_t backup_id, bool no_validate, bool
 else
 {
 if ((full_backup->status == BACKUP_STATUS_MERGED ||
-full_backup->status == BACKUP_STATUS_MERGED) &&
+full_backup->status == BACKUP_STATUS_MERGING) &&
 dest_backup->start_time != full_backup->merge_dest_backup)
 {
 elog(ERROR, "Full backup %s has unfinished merge with backup %s",

tests/merge_test.py

@@ -2734,5 +2734,46 @@ def test_merge_pg_filenode_map(self):
 'postgres',
 'select 1')
 
+def test_unfinished_merge(self):
+""" Test when parent has unfinished merge with a different backup. """
+self._check_gdb_flag_or_skip_test()
+cases = [('fail_merged', 'write_backup_filelist', ['MERGED', 'MERGING', 'OK']),
+('fail_merging', 'pgBackupWriteControl', ['MERGING', 'OK', 'OK'])]
+
+for name, terminate_at, states in cases:
+node_name = 'node_' + name
+backup_dir = os.path.join(self.tmp_path, self.module_name, self.fname, name)
+node = self.make_simple_node(
+base_dir=os.path.join(self.module_name, self.fname, node_name),
+set_replication=True,
+initdb_params=['--data-checksums'])
+
+self.init_pb(backup_dir)
+self.add_instance(backup_dir, node_name, node)
+self.set_archiving(backup_dir, node_name, node)
+node.slow_start()
+
+full_id=self.backup_node(backup_dir, node_name, node, options=['--stream'])
+
+backup_id = self.backup_node(backup_dir, node_name, node, backup_type='delta')
+second_backup_id = self.backup_node(backup_dir, node_name, node, backup_type='delta')
+
+gdb = self.merge_backup(backup_dir, node_name, backup_id, gdb=True)
+gdb.set_breakpoint(terminate_at)
+gdb.run_until_break()
+
+gdb.remove_all_breakpoints()
+gdb._execute('signal SIGINT')
+gdb.continue_execution_until_error()
+
+print(self.show_pb(backup_dir, node_name, as_json=False, as_text=True))
+
+for expected, real in zip(states, self.show_pb(backup_dir, node_name), strict=True):
+self.assertEqual(expected, real['status'])
+
+with self.assertRaisesRegex(ProbackupException,
+f"Full backup {full_id} has unfinished merge with backup {backup_id}"):
+self.merge_backup(backup_dir, node_name, second_backup_id, gdb=False)
+
 # 1. Need new test with corrupted FULL backup
 # 2. different compression levels