Switch to separate config file version

Use a separately incremented integer to track the configuration file
format version. We start with 2 due to the change that 23c3a951f6
introduced. 1 is declared to be equivalent to the original '0.10'.

The separate versioning has the advantage of being able to increment it
already during the development cycle, and using it with config files
that test/exploit the new format.

Using an integer has the advantages of a) differentiating it clearly
from the now independent kas version and b) simplifying the version
parsing. We can now also remove the string type restriction.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>

kas/__init__.py

@@ -24,7 +24,7 @@
 """
 
 from .__version__ import __version__
-from .__version__ import __compatible_version__
+from .__version__ import __file_version__, __compatible_file_version__
 
 __license__ = 'MIT'
 __copyright__ = 'Copyright (c) Siemens AG, 2017'

kas/__version__.py

@@ -26,4 +26,5 @@ __license__ = 'MIT'
 __copyright__ = 'Copyright (c) Siemens AG, 2017'
 
 __version__ = '0.10.0'
-__compatible_version__ = '0.10'
+__file_version__ = 2
+__compatible_file_version__ = 1

kas/includehandler.py

@@ -29,14 +29,8 @@ import os
 import collections
 import functools
 import logging
-try:
-    # pylint: disable=no-name-in-module
-    from distutils.version import StrictVersion
-except ImportError as exc:
-    logging.error("Could not import StrictVersion")
-    raise exc
 
-from . import __version__, __compatible_version__
+from . import __file_version__, __compatible_file_version__
 
 __license__ = 'MIT'
 __copyright__ = 'Copyright (c) Siemens AG, 2017'
@@ -78,38 +72,29 @@ def load_config(filename):
         raise LoadConfigException('Header missing or empty', filename)
 
     try:
-        file_version_string = header.get('version', None)
+        version = header.get('version', None)
     except AttributeError:
         raise LoadConfigException('Header is not a dictionary', filename)
 
-    if not file_version_string:
+    if not version:
         raise LoadConfigException('Version missing or empty', filename)
 
     try:
-        if not isinstance(file_version_string, str):
-            raise LoadConfigException('Version has to be a string',
-                                      filename)
-
-        file_version = StrictVersion()
-        file_version.parse(file_version_string)
-        kas_version = StrictVersion()
-        kas_version.parse(__version__)
-        lower_version = StrictVersion()
-        lower_version.parse(__compatible_version__)
-
-        # Remove patch version, because we provide limited forwards
-        # compatibility:
-        if file_version.version[2] > 0:
-            file_version.prerelease = None
-            file_version.version = tuple(list(file_version.version[:2]) + [0])
-
-        if file_version < lower_version or kas_version < file_version:
-            raise LoadConfigException('This version of kas is compatible with '
-                                      'version {} to {}, file has version {}'
-                                      .format(lower_version, kas_version,
-                                              file_version), filename)
+        version_value = int(version)
     except ValueError:
-        raise LoadConfigException('Not expected version format', filename)
+        # Be compatible: version string '0.10' is equivalent to file version 1
+        if isinstance(version, str) and version == '0.10':
+            version_value = 1
+        else:
+            raise LoadConfigException('Unexpected version format', filename)
+
+    if version_value < __compatible_file_version__ or \
+       version_value > __file_version__:
+        raise LoadConfigException('This version of kas is compatible with '
+                                  'version {} to {}, file has version {}'
+                                  .format(__compatible_file_version__,
+                                          __file_version__, version_value),
+                                  filename)
 
     return config