Add support for Baserock definitions version 7

This adds a new 'Defaults' class to represent definitions defaults

The Python 'jsonschema' module is used to validate the contents of the
Defaults file. This module is already included in Baserock 'build' and
'devel' reference systems by way of the 'openstack-common' stratum.

This commit embeds a copy of the JSON-Schema schema for the DEFAULTS
file. I think the canonical location of this schema should be in the
reference definitions.git, for now. In future, the schemas should maybe
have their own repos. Either way, Morph should embed a copy for the time
being so that we are sure the schema matches how Morph expects to parse
the file.

Morph's automated tests are all updated to use definitions version 7.
I removed most of the tests for built-in build systems, because the
built-ins themselves are no longer part of Morph. Only the mechanism for
defining them needs to be tested now.

Change-Id: I65f8f1c967683ef605852bfae5c68518e53f9981

1 files changed, 108 insertions, 0 deletions

diff --git a/morphlib/defaults.py b/morphlib/defaults.py
new file mode 100644
index 00000000..9e695a90
--- /dev/null
+++ b/morphlib/defaults.py
@@ -0,0 +1,108 @@
+# Copyright (C) 2015  Codethink Limited
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; version 2 of the License.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License along
+# with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+# =*= License: GPL-2 =*=
+
+
+import cliapp
+import jsonschema
+import yaml
+
+import os
+
+import morphlib
+
+
+class Defaults(object):
+    '''Represents predefined default values specific to Baserock definitions.
+
+    The DEFAULTS file was added in definitions format version 7, which lets
+    users set these defaults. The text of DEFAULTS file can be passed in as
+    'text', and will be validated and parsed if definitions_version >= 7.
+
+    Prior to version 7, the defaults were hardcoded in Morph. These defaults
+    will be returned if definitions_version < 7.
+
+    '''
+    def __init__(self, definitions_version, text=None):
+        self._build_systems = {}
+        self._split_rules = {}
+
+        schema_path = os.path.join(morphlib.util.schemas_directory(),
+                                   'defaults.json-schema')
+        with open(schema_path) as f:
+            self.schema = yaml.load(f)
+
+        if definitions_version >= 7:
+            if text:
+                self._build_systems, self._split_rules = self._parse(text)
+        else:
+            self._build_systems, self._split_rules = self._builtins()
+
+    def _parse(self, text):
+        build_systems = {}
+        split_rules = {}
+
+        # This reports errors against <string> rather than the actual filename,
+        # which is sad.
+        data = yaml.safe_load(text)
+
+        if data is None:
+            # It's OK to be empty, I guess.
+            return build_systems, split_rules
+
+        try:
+            # It would be nice if this could give line numbers when it spotted
+            # errors. Seems tricky.
+            jsonschema.validate(data, self.schema)
+        except jsonschema.ValidationError as e:
+            raise cliapp.AppException('Invalid DEFAULTS file: %s' % e.message)
+
+        build_system_data = data.get('build-systems', {})
+        for name, commands in build_system_data.items():
+            build_system = morphlib.buildsystem.BuildSystem()
+            build_system.from_dict(name, commands)
+            build_systems[name] = build_system
+
+        # It would make sense to create artifactsplitrule.SplitRule instances
+        # here, instead of an unlabelled data structure. That would need some
+        # changes to source.make_sources() and the 'artifactsplitrule' module.
+        split_rules_data = data.get('split-rules', {})
+        for kind, rules in split_rules_data.items():
+            split_rules[kind] = []
+            for rule in rules:
+                rule_unlabelled = (rule['artifact'], rule['include'])
+                split_rules[kind].append(rule_unlabelled)
+
+        return build_systems, split_rules
+
+    def _builtins(self):
+        build_systems = {}
+        split_rules = {}
+
+        for build_system in morphlib.buildsystem.build_systems:
+            build_systems[build_system.name] = build_system
+
+        split_rules['chunk'] = \
+            morphlib.artifactsplitrule.DEFAULT_CHUNK_RULES
+        split_rules['stratum'] = \
+            morphlib.artifactsplitrule.DEFAULT_STRATUM_RULES
+
+        return build_systems, split_rules
+
+    def build_systems(self):
+        return self._build_systems
+
+    def split_rules(self):
+        return self._split_rules