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from sqlalchemy import util
class ClauseVisitor(object):
__traverse_options__ = {}
def traverse_single(self, obj):
for v in self._iterate_visitors:
meth = getattr(v, "visit_%s" % obj.__visit_name__, None)
if meth:
return meth(obj)
def iterate(self, obj):
"""traverse the given expression structure, returning an iterator of all elements."""
return iterate(obj, self.__traverse_options__)
def traverse(self, obj):
"""traverse and visit the given expression structure."""
visitors = {}
for name in dir(self):
if name.startswith('visit_'):
visitors[name[6:]] = getattr(self, name)
return traverse(obj, self.__traverse_options__, visitors)
def _iterate_visitors(self):
"""iterate through this visitor and each 'chained' visitor."""
v = self
while v:
yield v
v = getattr(v, '_next', None)
_iterate_visitors = property(_iterate_visitors)
def chain(self, visitor):
"""'chain' an additional ClauseVisitor onto this ClauseVisitor.
the chained visitor will receive all visit events after this one.
"""
tail = list(self._iterate_visitors)[-1]
tail._next = visitor
return self
class CloningVisitor(ClauseVisitor):
def copy_and_process(self, list_):
"""Apply cloned traversal to the given list of elements, and return the new list."""
return [self.traverse(x) for x in list_]
def traverse(self, obj):
"""traverse and visit the given expression structure."""
visitors = {}
for name in dir(self):
if name.startswith('visit_'):
visitors[name[6:]] = getattr(self, name)
return cloned_traverse(obj, self.__traverse_options__, visitors)
class ReplacingCloningVisitor(CloningVisitor):
def replace(self, elem):
"""receive pre-copied elements during a cloning traversal.
If the method returns a new element, the element is used
instead of creating a simple copy of the element. Traversal
will halt on the newly returned element if it is re-encountered.
"""
return None
def traverse(self, obj):
"""traverse and visit the given expression structure."""
def replace(elem):
for v in self._iterate_visitors:
e = v.replace(elem)
if e:
return e
return replacement_traverse(obj, self.__traverse_options__, replace)
def iterate(obj, opts):
"""traverse the given expression structure, returning an iterator.
traversal is configured to be breadth-first.
"""
stack = util.deque([obj])
while stack:
t = stack.popleft()
yield t
for c in t.get_children(**opts):
stack.append(c)
def iterate_depthfirst(obj, opts):
"""traverse the given expression structure, returning an iterator.
traversal is configured to be depth-first.
"""
stack = util.deque([obj])
traversal = util.deque()
while stack:
t = stack.pop()
traversal.appendleft(t)
for c in t.get_children(**opts):
stack.append(c)
return iter(traversal)
def traverse_using(iterator, obj, visitors):
"""visit the given expression structure using the given iterator of objects."""
for target in iterator:
meth = visitors.get(target.__visit_name__, None)
if meth:
meth(target)
return obj
def traverse(obj, opts, visitors):
"""traverse and visit the given expression structure using the default iterator."""
return traverse_using(iterate(obj, opts), obj, visitors)
def traverse_depthfirst(obj, opts, visitors):
"""traverse and visit the given expression structure using the depth-first iterator."""
return traverse_using(iterate_depthfirst(obj, opts), obj, visitors)
def cloned_traverse(obj, opts, visitors):
cloned = {}
def clone(element):
if element not in cloned:
cloned[element] = element._clone()
return cloned[element]
obj = clone(obj)
stack = [obj]
while stack:
t = stack.pop()
if t in cloned:
continue
t._copy_internals(clone=clone)
meth = visitors.get(t.__visit_name__, None)
if meth:
meth(t)
for c in t.get_children(**opts):
stack.append(c)
return obj
def replacement_traverse(obj, opts, replace):
cloned = {}
stop_on = util.Set(opts.get('stop_on', []))
def clone(element):
newelem = replace(element)
if newelem:
stop_on.add(newelem)
return newelem
if element not in cloned:
cloned[element] = element._clone()
return cloned[element]
obj = clone(obj)
stack = [obj]
while stack:
t = stack.pop()
if t in stop_on:
continue
t._copy_internals(clone=clone)
for c in t.get_children(**opts):
stack.append(c)
return obj
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