Python code coverage for Lib/compiler/visitor.py

#	count	content
1	2	from compiler import ast
2	n/a
3	n/a	# XXX should probably rename ASTVisitor to ASTWalker
4	n/a	# XXX can it be made even more generic?
5	n/a
6	4	class ASTVisitor:
7	n/a	"""Performs a depth-first walk of the AST
8	n/a
9	n/a	The ASTVisitor will walk the AST, performing either a preorder or
10	n/a	postorder traversal depending on which method is called.
11	n/a
12	n/a	methods:
13	n/a	preorder(tree, visitor)
14	n/a	postorder(tree, visitor)
15	n/a	tree: an instance of ast.Node
16	n/a	visitor: an instance with visitXXX methods
17	n/a
18	n/a	The ASTVisitor is responsible for walking over the tree in the
19	n/a	correct order. For each node, it checks the visitor argument for
20	n/a	a method named 'visitNodeType' where NodeType is the name of the
21	n/a	node's class, e.g. Class. If the method exists, it is called
22	n/a	with the node as its sole argument.
23	n/a
24	n/a	The visitor method for a particular node type can control how
25	n/a	child nodes are visited during a preorder walk. (It can't control
26	n/a	the order during a postorder walk, because it is called _after_
27	n/a	the walk has occurred.) The ASTVisitor modifies the visitor
28	n/a	argument by adding a visit method to the visitor; this method can
29	n/a	be used to visit a child node of arbitrary type.
30	2	"""
31	n/a
32	2	VERBOSE = 0
33	n/a
34	2	def __init__(self):
35	2244	self.node = None
36	2244	self._cache = {}
37	n/a
38	2	def default(self, node, *args):
39	174388	for child in node.getChildNodes():
40	92479	self.dispatch(child, *args)
41	n/a
42	2	def dispatch(self, node, *args):
43	118685	self.node = node
44	118685	klass = node.__class__
45	118685	meth = self._cache.get(klass, None)
46	118685	if meth is None:
47	13115	className = klass.__name__
48	13115	meth = getattr(self.visitor, 'visit' + className, self.default)
49	13115	self._cache[klass] = meth
50	n/a	## if self.VERBOSE > 0:
51	n/a	## className = klass.__name__
52	n/a	## if self.VERBOSE == 1:
53	n/a	## if meth == 0:
54	n/a	## print "dispatch", className
55	n/a	## else:
56	n/a	## print "dispatch", className, (meth and meth.__name__ or '')
57	118685	return meth(node, *args)
58	n/a
59	2	def preorder(self, tree, visitor, *args):
60	n/a	"""Do preorder walk of tree using visitor"""
61	2244	self.visitor = visitor
62	2244	visitor.visit = self.dispatch
63	2244	self.dispatch(tree, args) # XXX args make sense?
64	n/a
65	4	class ExampleASTVisitor(ASTVisitor):
66	n/a	"""Prints examples of the nodes that aren't visited
67	n/a
68	n/a	This visitor-driver is only useful for development, when it's
69	n/a	helpful to develop a visitor incrementally, and get feedback on what
70	n/a	you still have to do.
71	2	"""
72	2	examples = {}
73	n/a
74	2	def dispatch(self, node, *args):
75	0	self.node = node
76	0	meth = self._cache.get(node.__class__, None)
77	0	className = node.__class__.__name__
78	0	if meth is None:
79	0	meth = getattr(self.visitor, 'visit' + className, 0)
80	0	self._cache[node.__class__] = meth
81	0	if self.VERBOSE > 1:
82	0	print "dispatch", className, (meth and meth.__name__ or '')
83	0	if meth:
84	0	meth(node, *args)
85	0	elif self.VERBOSE > 0:
86	0	klass = node.__class__
87	0	if klass not in self.examples:
88	0	self.examples[klass] = klass
89	0	print
90	0	print self.visitor
91	0	print klass
92	0	for attr in dir(node):
93	0	if attr[0] != '_':
94	0	print "\t", "%-12.12s" % attr, getattr(node, attr)
95	0	print
96	0	return self.default(node, *args)
97	n/a
98	n/a	# XXX this is an API change
99	n/a
100	2	_walker = ASTVisitor
101	2	def walk(tree, visitor, walker=None, verbose=None):
102	2244	if walker is None:
103	2244	walker = _walker()
104	2244	if verbose is not None:
105	1085	walker.VERBOSE = verbose
106	2244	walker.preorder(tree, visitor)
107	2244	return walker.visitor
108	n/a
109	2	def dumpNode(node):
110	0	print node.__class__
111	0	for attr in dir(node):
112	0	if attr[0] != '_':
113	0	print "\t", "%-10.10s" % attr, getattr(node, attr)