1 files changed, 303 insertions, 0 deletions
diff --git a/Lib/lib2to3/fixes/util.py b/Lib/lib2to3/fixes/util.py
new file mode 100644
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+++ b/Lib/lib2to3/fixes/util.py
@@ -0,0 +1,303 @@
+"""Utility functions, node construction macros, etc."""
+# Author: Collin Winter
+
+# Local imports
+from ..pgen2 import token
+from ..pytree import Leaf, Node
+from ..pygram import python_symbols as syms
+
+
+###########################################################
+### Common node-construction "macros"
+###########################################################
+
+def KeywordArg(keyword, value):
+    return Node(syms.argument,
+                [keyword, Leaf(token.EQUAL, '='), value])
+
+def LParen():
+    return Leaf(token.LPAR, "(")
+
+def RParen():
+    return Leaf(token.RPAR, ")")
+
+def Assign(target, source):
+    """Build an assignment statement"""
+    if not isinstance(target, list):
+        target = [target]
+    if not isinstance(source, list):
+        source.set_prefix(" ")
+        source = [source]
+
+    return Node(syms.atom,
+                target + [Leaf(token.EQUAL, "=", prefix=" ")] + source)
+
+def Name(name, prefix=None):
+    """Return a NAME leaf"""
+    return Leaf(token.NAME, name, prefix=prefix)
+
+def Attr(obj, attr):
+    """A node tuple for obj.attr"""
+    return [obj, Node(syms.trailer, [Dot(), attr])]
+
+def Comma():
+    """A comma leaf"""
+    return Leaf(token.COMMA, ",")
+
+def Dot():
+    """A period (.) leaf"""
+    return Leaf(token.DOT, ".")
+
+def ArgList(args, lparen=LParen(), rparen=RParen()):
+    """A parenthesised argument list, used by Call()"""
+    return Node(syms.trailer,
+                [lparen.clone(),
+                 Node(syms.arglist, args),
+                 rparen.clone()])
+
+def Call(func_name, args, prefix=None):
+    """A function call"""
+    node = Node(syms.power, [func_name, ArgList(args)])
+    if prefix is not None:
+        node.set_prefix(prefix)
+    return node
+
+def Newline():
+    """A newline literal"""
+    return Leaf(token.NEWLINE, "\n")
+
+def BlankLine():
+    """A blank line"""
+    return Leaf(token.NEWLINE, "")
+
+def Number(n, prefix=None):
+    return Leaf(token.NUMBER, n, prefix=prefix)
+
+def Subscript(index_node):
+    """A numeric or string subscript"""
+    return Node(syms.trailer, [Leaf(token.LBRACE, '['),
+                               index_node,
+                               Leaf(token.RBRACE, ']')])
+
+def String(string, prefix=None):
+    """A string leaf"""
+    return Leaf(token.STRING, string, prefix=prefix)
+
+def ListComp(xp, fp, it, test=None):
+    """A list comprehension of the form [xp for fp in it if test].
+
+    If test is None, the "if test" part is omitted.
+    """
+    xp.set_prefix("")
+    fp.set_prefix(" ")
+    it.set_prefix(" ")
+    for_leaf = Leaf(token.NAME, "for")
+    for_leaf.set_prefix(" ")
+    in_leaf = Leaf(token.NAME, "in")
+    in_leaf.set_prefix(" ")
+    inner_args = [for_leaf, fp, in_leaf, it]
+    if test:
+        test.set_prefix(" ")
+        if_leaf = Leaf(token.NAME, "if")
+        if_leaf.set_prefix(" ")
+        inner_args.append(Node(syms.comp_if, [if_leaf, test]))
+    inner = Node(syms.listmaker, [xp, Node(syms.comp_for, inner_args)])
+    return Node(syms.atom,
+                       [Leaf(token.LBRACE, "["),
+                        inner,
+                        Leaf(token.RBRACE, "]")])
+
+###########################################################
+### Determine whether a node represents a given literal
+###########################################################
+
+def is_tuple(node):
+    """Does the node represent a tuple literal?"""
+    if isinstance(node, Node) and node.children == [LParen(), RParen()]:
+        return True
+    return (isinstance(node, Node)
+            and len(node.children) == 3
+            and isinstance(node.children[0], Leaf)
+            and isinstance(node.children[1], Node)
+            and isinstance(node.children[2], Leaf)
+            and node.children[0].value == "("
+            and node.children[2].value == ")")
+
+def is_list(node):
+    """Does the node represent a list literal?"""
+    return (isinstance(node, Node)
+            and len(node.children) > 1
+            and isinstance(node.children[0], Leaf)
+            and isinstance(node.children[-1], Leaf)
+            and node.children[0].value == "["
+            and node.children[-1].value == "]")
+
+###########################################################
+### Common portability code. This allows fixers to do, eg,
+###  "from .util import set" and forget about it.
+###########################################################
+
+try:
+    any = any
+except NameError:
+    def any(l):
+        for o in l:
+            if o:
+                return True
+        return False
+
+try:
+    set = set
+except NameError:
+    from sets import Set as set
+
+try:
+    reversed = reversed
+except NameError:
+    def reversed(l):
+        return l[::-1]
+
+###########################################################
+### Misc
+###########################################################
+
+def attr_chain(obj, attr):
+    """Follow an attribute chain.
+    
+    If you have a chain of objects where a.foo -> b, b.foo-> c, etc,
+    use this to iterate over all objects in the chain. Iteration is
+    terminated by getattr(x, attr) is None.
+    
+    Args:
+        obj: the starting object
+        attr: the name of the chaining attribute
+    
+    Yields:
+        Each successive object in the chain.
+    """
+    next = getattr(obj, attr)
+    while next:
+        yield next
+        next = getattr(next, attr)
+
+###########################################################
+### The following functions are to find bindings in a suite
+###########################################################
+
+def make_suite(node):
+    if node.type == syms.suite:
+        return node
+    node = node.clone()
+    parent, node.parent = node.parent, None
+    suite = Node(syms.suite, [node])
+    suite.parent = parent
+    return suite
+
+def does_tree_import(package, name, node):
+    """ Returns true if name is imported from package at the
+        top level of the tree which node belongs to.
+        To cover the case of an import like 'import foo', use
+        Null for the package and 'foo' for the name. """
+    # Scamper up to the top level namespace
+    while node.type != syms.file_input:
+        assert node.parent, "Tree is insane! root found before "\
+                           "file_input node was found."
+        node = node.parent
+
+    binding = find_binding(name, node, package)
+    return bool(binding)
+
+_def_syms = set([syms.classdef, syms.funcdef])
+def find_binding(name, node, package=None):
+    """ Returns the node which binds variable name, otherwise None.
+        If optional argument package is supplied, only imports will
+        be returned.
+        See test cases for examples."""
+    for child in node.children:
+        ret = None
+        if child.type == syms.for_stmt:
+            if _find(name, child.children[1]):
+                return child
+            n = find_binding(name, make_suite(child.children[-1]), package)
+            if n: ret = n
+        elif child.type in (syms.if_stmt, syms.while_stmt):
+            n = find_binding(name, make_suite(child.children[-1]), package)
+            if n: ret = n
+        elif child.type == syms.try_stmt:
+            n = find_binding(name, make_suite(child.children[2]), package)
+            if n:
+                ret = n
+            else:
+                for i, kid in enumerate(child.children[3:]):
+                    if kid.type == token.COLON and kid.value == ":":
+                        # i+3 is the colon, i+4 is the suite
+                        n = find_binding(name, make_suite(child.children[i+4]), package)
+                        if n: ret = n
+        elif child.type in _def_syms and child.children[1].value == name:
+            ret = child
+        elif _is_import_binding(child, name, package):
+            ret = child
+        elif child.type == syms.simple_stmt:
+            ret = find_binding(name, child, package)
+        elif child.type == syms.expr_stmt:
+                if _find(name, child.children[0]):
+                    ret = child
+
+        if ret:
+            if not package:
+                return ret
+            if ret.type in (syms.import_name, syms.import_from):
+                return ret
+    return None
+
+_block_syms = set([syms.funcdef, syms.classdef, syms.trailer])
+def _find(name, node):
+    nodes = [node]
+    while nodes:
+        node = nodes.pop()
+        if node.type > 256 and node.type not in _block_syms:
+            nodes.extend(node.children)
+        elif node.type == token.NAME and node.value == name:
+            return node
+    return None
+
+def _is_import_binding(node, name, package=None):
+    """ Will reuturn node if node will import name, or node
+        will import * from package.  None is returned otherwise.
+        See test cases for examples. """
+
+    if node.type == syms.import_name and not package:
+        imp = node.children[1]
+        if imp.type == syms.dotted_as_names:
+            for child in imp.children:
+                if child.type == syms.dotted_as_name:
+                    if child.children[2].value == name:
+                        return node
+                elif child.type == token.NAME and child.value == name:
+                    return node
+        elif imp.type == syms.dotted_as_name:
+            last = imp.children[-1]
+            if last.type == token.NAME and last.value == name:
+                return node
+        elif imp.type == token.NAME and imp.value == name:
+            return node
+    elif node.type == syms.import_from:
+        # unicode(...) is used to make life easier here, because
+        # from a.b import parses to ['import', ['a', '.', 'b'], ...]
+        if package and unicode(node.children[1]).strip() != package:
+            return None
+        n = node.children[3]
+        if package and _find('as', n):
+            # See test_from_import_as for explanation
+            return None
+        elif n.type == syms.import_as_names and _find(name, n):
+            return node
+        elif n.type == syms.import_as_name:
+            child = n.children[2]
+            if child.type == token.NAME and child.value == name:
+                return node
+        elif n.type == token.NAME and n.value == name:
+            return node
+        elif package and n.type == token.STAR:
+            return node
+    return None