Add future 0.18.2

lib/libfuturize/fixes/fix_next_call.py

@@ -0,0 +1,104 @@
+"""
+Based on fix_next.py by Collin Winter.
+
+Replaces it.next() -> next(it), per PEP 3114.
+
+Unlike fix_next.py, this fixer doesn't replace the name of a next method with __next__,
+which would break Python 2 compatibility without further help from fixers in
+stage 2.
+"""
+
+# Local imports
+from lib2to3.pgen2 import token
+from lib2to3.pygram import python_symbols as syms
+from lib2to3 import fixer_base
+from lib2to3.fixer_util import Name, Call, find_binding
+
+bind_warning = "Calls to builtin next() possibly shadowed by global binding"
+
+
+class FixNextCall(fixer_base.BaseFix):
+    BM_compatible = True
+    PATTERN = """
+    power< base=any+ trailer< '.' attr='next' > trailer< '(' ')' > >
+    |
+    power< head=any+ trailer< '.' attr='next' > not trailer< '(' ')' > >
+    |
+    global=global_stmt< 'global' any* 'next' any* >
+    """
+
+    order = "pre" # Pre-order tree traversal
+
+    def start_tree(self, tree, filename):
+        super(FixNextCall, self).start_tree(tree, filename)
+
+        n = find_binding('next', tree)
+        if n:
+            self.warning(n, bind_warning)
+            self.shadowed_next = True
+        else:
+            self.shadowed_next = False
+
+    def transform(self, node, results):
+        assert results
+
+        base = results.get("base")
+        attr = results.get("attr")
+        name = results.get("name")
+
+        if base:
+            if self.shadowed_next:
+                # Omit this:
+                # attr.replace(Name("__next__", prefix=attr.prefix))
+                pass
+            else:
+                base = [n.clone() for n in base]
+                base[0].prefix = ""
+                node.replace(Call(Name("next", prefix=node.prefix), base))
+        elif name:
+            # Omit this:
+            # n = Name("__next__", prefix=name.prefix)
+            # name.replace(n)
+            pass
+        elif attr:
+            # We don't do this transformation if we're assigning to "x.next".
+            # Unfortunately, it doesn't seem possible to do this in PATTERN,
+            #  so it's being done here.
+            if is_assign_target(node):
+                head = results["head"]
+                if "".join([str(n) for n in head]).strip() == '__builtin__':
+                    self.warning(node, bind_warning)
+                return
+            # Omit this:
+            # attr.replace(Name("__next__"))
+        elif "global" in results:
+            self.warning(node, bind_warning)
+            self.shadowed_next = True
+
+
+### The following functions help test if node is part of an assignment
+###  target.
+
+def is_assign_target(node):
+    assign = find_assign(node)
+    if assign is None:
+        return False
+
+    for child in assign.children:
+        if child.type == token.EQUAL:
+            return False
+        elif is_subtree(child, node):
+            return True
+    return False
+
+def find_assign(node):
+    if node.type == syms.expr_stmt:
+        return node
+    if node.type == syms.simple_stmt or node.parent is None:
+        return None
+    return find_assign(node.parent)
+
+def is_subtree(root, node):
+    if root == node:
+        return True
+    return any(is_subtree(c, node) for c in root.children)