+RX_RESOLVE = RX.compile(r'(?x) \$ \[ ([^]]+) \]')
+
+class ConfigSyntaxError (ExpectedError):
+ def __init__(me, fname, lno, msg):
+ me.fname = fname
+ me.lno = lno
+ me.msg = msg
+ def __str__(me):
+ return '%s:%d: %s' % (me.fname, me.lno, me.msg)
+
+def _fmt_path(path):
+ return ' -> '.join(["`%s'" % hop for hop in path])
+
+class AmbiguousOptionError (ExpectedError):
+ def __init__(me, key, patha, vala, pathb, valb):
+ me.key = key
+ me.patha, me.vala = patha, vala
+ me.pathb, me.valb = pathb, valb
+ def __str__(me):
+ return "Ambiguous answer resolving key `%s': " \
+ "path %s yields `%s' but %s yields `%s'" % \
+ (me.key, _fmt_path(me.patha), me.vala, _fmt_path(me.pathb), me.valb)
+
+class InheritanceCycleError (ExpectedError):
+ def __init__(me, key, path):
+ me.key = key
+ me.path = path
+ def __str__(me):
+ return "Found a cycle %s looking up key `%s'" % \
+ (_fmt_path(me.path), me.key)
+
+class MissingSectionException (ExpectedError):
+ def __init__(me, sec):
+ me.sec = sec
+ def __str__(me):
+ return "Section `%s' not found" % (me.sec)
+
+class MissingKeyException (ExpectedError):
+ def __init__(me, sec, key):
+ me.sec = sec
+ me.key = key
+ def __str__(me):
+ return "Key `%s' not found in section `%s'" % (me.key, me.sec)
+
+class ConfigSection (object):
+ """
+ A section in a configuration parser.
+
+ This is where a lot of the nitty-gritty stuff actually happens. The
+ `MyConfigParser' knows a lot about the internals of this class, which saves
+ on building a complicated interface.
+ """
+
+ def __init__(me, name, cp):
+ """Initialize a new, empty section with a given NAME and parent CP."""
+
+ ## The cache maps item keys to entries, which consist of a pair of
+ ## objects. There are four possible states for a cache entry:
+ ##
+ ## * missing -- there is no entry at all with this key, so we must
+ ## search for it;
+ ##
+ ## * None, None -- we are actively trying to resolve this key, so if we
+ ## encounter this state, we have found a cycle in the inheritance
+ ## graph;
+ ##
+ ## * None, [] -- we know that this key isn't reachable through any of
+ ## our parents;
+ ##
+ ## * VALUE, PATH -- we know that the key resolves to VALUE, along the
+ ## PATH from us (exclusive) to the defining parent (inclusive).
+ me.name = name
+ me._itemmap = dict()
+ me._cache = dict()
+ me._cp = cp
+
+ def _expand(me, string, resolvep):
+ """
+ Expands $(...) and (optionally) $[...] placeholders in STRING.
+
+ RESOLVEP is a boolean switch: do we bother to tax the resolver or not?
+ This is turned off by MyConfigParser's resolve() method while it's
+ collecting hostnames to be resolved.
+ """
+ string = RX_REF.sub \
+ (lambda m: me.get(m.group(1), resolvep), string)
+ if resolvep:
+ string = RX_RESOLVE.sub(lambda m: me._cp._resolver.lookup(m.group(1)),
+ string)
+ return string
+
+ def _parents(me):
+ """Yield this section's parents."""
+ try: names = me._itemmap['@inherit']
+ except KeyError: return
+ for name in names.replace(',', ' ').split():
+ yield me._cp.section(name)
+
+ def _get(me, key, path = None):
+ """
+ Low-level option-fetching method.
+
+ Fetch the value for the named KEY in this section, or maybe (recursively)
+ a section which it inherits from.
+
+ Returns a pair VALUE, PATH. The value is not expanded; nor do we check
+ for the special `name' key. The caller is expected to do these things.
+ Returns None if no value could be found.
+ """
+
+ ## If we weren't given a path, then we'd better make one.
+ if path is None: path = []
+
+ ## Extend the path to cover us, but remember to remove us again when
+ ## we've finished. If we need to pass the current path back upwards,
+ ## then remember to take a copy.
+ path.append(me.name)
+ try:
+
+ ## If we've been this way before on another pass through then return the
+ ## value we found then. If we're still thinking about it then we've
+ ## found a cycle.
+ try: v, p = me._cache[key]
+ except KeyError: pass
+ else:
+ if p is None: raise InheritanceCycleError(key, path[:])
+ else: return v, path + p
+
+ ## See whether the answer is ready waiting for us.
+ try: v = me._itemmap[key]
+ except KeyError: pass
+ else:
+ p = path[:]
+ me._cache[key] = v, []
+ return v, p
+
+ ## Initially we have no idea.
+ value = None
+ winner = []
+
+ ## Go through our parents and ask them what they think.
+ me._cache[key] = None, None
+ for p in me._parents():
+
+ ## See whether we get an answer. If not, keep on going.
+ v, pp = p._get(key, path)
+ if v is None: continue
+
+ ## If we got an answer, check that it matches any previous ones.
+ if value is None:
+ value = v
+ winner = pp
+ elif value != v:
+ raise AmbiguousOptionError(key, winner, value, pp, v)
+
+ ## That's the best we could manage.
+ me._cache[key] = value, winner[len(path):]
+ return value, winner
+
+ finally:
+ ## Remove us from the path again.
+ path.pop()
+
+ def get(me, key, resolvep = True):
+ """
+ Retrieve the value of KEY from this section.
+ """
~mdw / tripe / blobdiff