def instantiate_spec(spec_cls, data):
"""Instantiates specification accounting for specification hierarchies.
:param spec_cls: Specification concrete or base class. In case if base
class or the hierarchy is provided this method relies on attributes
_polymorphic_key and _polymorphic_value in order to find a concrete
class that needs to be instantiated.
:param data: Raw specification data as a dictionary.
"""
if issubclass(spec_cls, BaseSpecList):
# Ignore polymorphic search for specification lists because
# it doesn't make sense for them.
return spec_cls(data)
if not hasattr(spec_cls, '_polymorphic_key'):
spec = spec_cls(data)
spec.validate_semantics()
return spec
# In order to do polymorphic search we need to make sure that
# a spec is backed by a dictionary. Otherwise we can't extract
# a polymorphic key.
if not isinstance(data, dict):
raise exc.InvalidModelException(
"A specification with polymorphic key must be backed by"
" a dictionary [spec_cls=%s, data=%s]" % (spec_cls, data))
key = spec_cls._polymorphic_key
if not isinstance(key, tuple):
key_name = key
key_default = None
else:
key_name = key[0]
key_default = key[1]
for cls in utils.iter_subclasses(spec_cls):
if not hasattr(cls, '_polymorphic_value'):
raise exc.DSLParsingException(
"Class '%s' is expected to have attribute '_polymorphic_value'"
" because it's a part of specification hierarchy inherited "
"from class '%s'." % (cls, spec_cls))
if cls._polymorphic_value == data.get(key_name, key_default):
spec = cls(data)
spec.validate_semantics()
return spec
raise exc.DSLParsingException(
'Failed to find a specification class to instantiate '
'[spec_cls=%s, data=%s]' % (spec_cls, data))
def _get_spec_version(spec_dict):
# If version is not specified it will '2.0' by default.
ver = V2_0
if 'version' in spec_dict:
ver = spec_dict['version']
if not ver or str(float(ver)) not in ALL_VERSIONS:
raise exc.DSLParsingException('Unsupported DSL version: %s' % ver)
return ver
def parse_yaml(text):
"""Loads a text in YAML format as dictionary object.
:param text: YAML text.
:return: Parsed YAML document as dictionary.
"""
try:
return yaml.safe_load(text) or {}
except error.YAMLError as e:
raise exc.DSLParsingException("Definition could not be parsed: %s\n" %
e)
def validate_semantics(self):
super(DirectWorkflowSpec, self).validate_semantics()
# Check if there are start tasks.
if not self.find_start_tasks():
raise exc.DSLParsingException(
'Failed to find start tasks in direct workflow. '
'There must be at least one task without inbound transition.'
'[workflow_name=%s]' % self._name)
self._check_workflow_integrity()
self._check_join_tasks()
def _raise(ver):
raise exc.DSLParsingException('Unsupported DSL version: %s' % ver)
