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# Copyright (C) 2012 Yahoo! Inc.
#
# Author: Joshua Harlow <harlowja@yahoo-inc.com>
#
# This file is part of cloud-init. See LICENSE file for license information.
import re
from cloudinit import importer, type_utils
NAME_MTCH = re.compile(r"(^[a-zA-Z_][A-Za-z0-9_]*)\((.*?)\)$")
DEF_MERGE_TYPE = "list()+dict()+str()"
MERGER_PREFIX = "m_"
MERGER_ATTR = "Merger"
class UnknownMerger(object):
# Named differently so auto-method finding
# doesn't pick this up if there is ever a type
# named "unknown"
def _handle_unknown(self, _meth_wanted, value, _merge_with):
return value
# This merging will attempt to look for a '_on_X' method
# in our own object for a given object Y with type X,
# if found it will be called to perform the merge of a source
# object and a object to merge_with.
#
# If not found the merge will be given to a '_handle_unknown'
# function which can decide what to do wit the 2 values.
def merge(self, source, merge_with):
type_name = type_utils.obj_name(source)
type_name = type_name.lower()
method_name = "_on_%s" % (type_name)
meth = None
args = [source, merge_with]
if hasattr(self, method_name):
meth = getattr(self, method_name)
if not meth:
meth = self._handle_unknown
args.insert(0, method_name)
return meth(*args)
class LookupMerger(UnknownMerger):
def __init__(self, lookups=None):
UnknownMerger.__init__(self)
if lookups is None:
self._lookups = []
else:
self._lookups = lookups
def __str__(self):
return "LookupMerger: (%s)" % (len(self._lookups))
# For items which can not be merged by the parent this object
# will lookup in a internally maintained set of objects and
# find which one of those objects can perform the merge. If
# any of the contained objects have the needed method, they
# will be called to perform the merge.
def _handle_unknown(self, meth_wanted, value, merge_with):
meth = None
for merger in self._lookups:
if hasattr(merger, meth_wanted):
# First one that has that method/attr gets to be
# the one that will be called
meth = getattr(merger, meth_wanted)
break
if not meth:
return UnknownMerger._handle_unknown(
self, meth_wanted, value, merge_with
)
return meth(value, merge_with)
def dict_extract_mergers(config):
parsed_mergers = []
raw_mergers = config.pop("merge_how", None)
if raw_mergers is None:
raw_mergers = config.pop("merge_type", None)
if raw_mergers is None:
return parsed_mergers
if isinstance(raw_mergers, str):
return string_extract_mergers(raw_mergers)
for m in raw_mergers:
if isinstance(m, (dict)):
name = m["name"]
name = name.replace("-", "_").strip()
opts = m["settings"]
else:
name = m[0]
if len(m) >= 2:
opts = m[1:]
else:
opts = []
if name:
parsed_mergers.append((name, opts))
return parsed_mergers
def string_extract_mergers(merge_how):
parsed_mergers = []
for m_name in merge_how.split("+"):
# Canonicalize the name (so that it can be found
# even when users alter it in various ways)
m_name = m_name.lower().strip()
m_name = m_name.replace("-", "_")
if not m_name:
continue
match = NAME_MTCH.match(m_name)
if not match:
msg = "Matcher identifer '%s' is not in the right format" % (
m_name
)
raise ValueError(msg)
(m_name, m_ops) = match.groups()
m_ops = m_ops.strip().split(",")
m_ops = [m.strip().lower() for m in m_ops if m.strip()]
parsed_mergers.append((m_name, m_ops))
return parsed_mergers
def default_mergers():
return tuple(string_extract_mergers(DEF_MERGE_TYPE))
def construct(parsed_mergers):
mergers_to_be = []
for (m_name, m_ops) in parsed_mergers:
if not m_name.startswith(MERGER_PREFIX):
m_name = MERGER_PREFIX + str(m_name)
merger_locs, looked_locs = importer.find_module(
m_name, [__name__], [MERGER_ATTR]
)
if not merger_locs:
msg = (
"Could not find merger module named '%s' "
"with attribute '%s' (searched %s)"
% (m_name, MERGER_ATTR, looked_locs)
)
raise ImportError(msg)
else:
mod = importer.import_module(merger_locs[0])
mod_attr = getattr(mod, MERGER_ATTR)
mergers_to_be.append((mod_attr, m_ops))
# Now form them...
mergers = []
root = LookupMerger(mergers)
for (attr, opts) in mergers_to_be:
mergers.append(attr(root, opts))
return root
# vi: ts=4 expandtab
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