Add a script to rewrite __future__ imports

maint/scripts/custom_fixers/fix_future_imports.py

@@ -0,0 +1,59 @@
+"""Updates all source files to import the same set of __future__ directives.
+"""
+from lib2to3 import fixer_base
+from lib2to3 import pytree
+from lib2to3.pgen2 import token
+from lib2to3.fixer_util import FromImport, Name, Comma, Newline
+
+# copied from fix_tuple_params.py
+def is_docstring(stmt):
+    return isinstance(stmt, pytree.Node) and \
+           stmt.children[0].type == token.STRING
+
+class FixFutureImports(fixer_base.BaseFix):
+    BM_compatible = True
+
+    PATTERN = """import_from< 'from' module_name="__future__" 'import' any >"""
+
+    def start_tree(self, tree, filename):
+        self.found_future_import = False
+
+    def new_future_import(self, old):
+        new = FromImport("__future__",
+                         [Name("absolute_import", prefix=" "), Comma(),
+                          Name("with_statement", prefix=" ")])
+        if old is not None:
+            new.prefix = old.prefix
+        return new
+
+    def transform(self, node, results):
+        self.found_future_import = True
+        return self.new_future_import(node)
+
+    def finish_tree(self, tree, filename):
+        if self.found_future_import:
+            return
+        if not isinstance(tree, pytree.Node):
+            # Empty files (usually __init__.py) show up as a single Leaf
+            # instead of a Node, so leave them alone
+            return
+        first_stmt = tree.children[0]
+        if is_docstring(first_stmt):
+            # Skip a line and add the import after the docstring
+            tree.insert_child(1, Newline())
+            pos = 2
+        elif first_stmt.prefix:
+            # No docstring, but an initial comment (perhaps a #! line).
+            # Transfer the initial comment to a new blank line.
+            newline = Newline()
+            newline.prefix = first_stmt.prefix
+            first_stmt.prefix = ""
+            tree.insert_child(0, newline)
+            pos = 1
+        else:
+            # No comments or docstring, just insert at the start
+            pos = 0
+        tree.insert_child(pos, self.new_future_import(None))
+        tree.insert_child(pos+1, Newline())  # terminates the import stmt
+
+

maint/scripts/run_fixers.py

@@ -0,0 +1,6 @@
+#!/usr/bin/env python
+
+import sys
+from lib2to3.main import main
+
+sys.exit(main("custom_fixers"))