use max header version number when merging configs

The header version cannot be merged in-order, as otherwise an include
file with a lower version defines the version of the merged config,
which might not be valid (e.g. if properties are used that are not
available in that version).

This aspect was irrelevant prior to introducing the dump plugin, as the
data is not used within kas. However, the dump plugin needs to use the
max header version as otherwise the generated config might not be valid.

Fixes: 5b3e238 ("add plugin to dump flattened config")
Signed-off-by: Felix Moessbauer <[email protected]>
Signed-off-by: Jan Kiszka <[email protected]>

docs/userguide/project-configuration.rst

@@ -132,7 +132,8 @@ be overwritten by the current file. While merging all the dictionaries are
 merged recursively while preserving the order in which the entries are added to
 the dictionary. This means that ``local_conf_header`` entries are added to the
 ``local.conf`` file in the same order in which they are defined in the
-different include files.
+different include files. The ``header.version`` property is always set to the
+highest version number found in the config files.
 
 Including configuration files via the command line
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

kas/includehandler.py

@@ -306,4 +306,8 @@ def _internal_dict_merge(dest, upd):
 
         config = functools.reduce(_internal_dict_merge,
                                   map(lambda x: x[1], configs))
+        # the merged config must have the highest (used) version number
+        header_version = max([int(cfg['header']['version'])
+                              for _, cfg in configs])
+        config['header']['version'] = header_version
         return config, missing_repos