SF patch #1438387, PEP 328: relative and absolute imports.

- IMPORT_NAME takes an extra argument from the stack: the relativeness of
   the import. Only passed to __import__ when it's not -1.

 - __import__() takes an optional 5th argument for the same thing; it
   __defaults to -1 (old semantics: try relative, then absolute)

 - 'from . import name' imports name (be it module or regular attribute)
   from the current module's *package*. Likewise, 'from .module import name'
   will import name from a sibling to the current module.

 - Importing from outside a package is not allowed; 'from . import sys' in a
   toplevel module will not work, nor will 'from .. import sys' in a
   (single-level) package.

 - 'from __future__ import absolute_import' will turn on the new semantics
   for import and from-import: imports will be absolute, except for
   from-import with dots.

Includes tests for regular imports and importhooks, parser changes and a
NEWS item, but no compiler-package changes or documentation changes.

Lib/test/test_ast.py

@@ -145,7 +145,7 @@ exec_results = [
 ('Module', [('TryFinally', [('Pass',)], [('Pass',)])]),
 ('Module', [('Assert', ('Name', 'v', ('Load',)), None)]),
 ('Module', [('Import', [('alias', 'sys', None)])]),
-('Module', [('ImportFrom', 'sys', [('alias', 'v', None)])]),
+('Module', [('ImportFrom', 'sys', [('alias', 'v', None)], 0)]),
 ('Module', [('Exec', ('Str', 'v'), None, None)]),
 ('Module', [('Global', ['v'])]),
 ('Module', [('Expr', ('Num', 1))]),

Lib/test/test_importhooks.py

@@ -12,6 +12,10 @@ def get_file():
     return __file__
 """
 
+absimp = "import sub\n"
+relimp = "from . import sub\n"
+futimp = "from __future__ import absolute_import\n"
+
 reload_src = test_src+"""\
 reloaded = True
 """
@@ -19,6 +23,11 @@ reloaded = True
 test_co = compile(test_src, "<???>", "exec")
 reload_co = compile(reload_src, "<???>", "exec")
 
+test2_oldabs_co = compile(absimp + test_src, "<???>", "exec")
+test2_newabs_co = compile(futimp + absimp + test_src, "<???>", "exec")
+test2_newrel_co = compile(relimp + test_src, "<???>", "exec")
+test2_futrel_co = compile(futimp + relimp + test_src, "<???>", "exec")
+
 test_path = "!!!_test_!!!"
 
 
@@ -38,6 +47,11 @@ class TestImporter:
         "hooktestpackage": (True, test_co),
         "hooktestpackage.sub": (True, test_co),
         "hooktestpackage.sub.subber": (False, test_co),
+        "hooktestpackage.oldabs": (False, test2_oldabs_co),
+        "hooktestpackage.newabs": (False, test2_newabs_co),
+        "hooktestpackage.newrel": (False, test2_newrel_co),
+        "hooktestpackage.futrel": (False, test2_futrel_co),
+        "sub": (False, test_co),
         "reloadmodule": (False, test_co),
     }
 
@@ -176,6 +190,32 @@ class ImportHooksTestCase(ImportHooksBaseTestCase):
         TestImporter.modules['reloadmodule'] = (False, reload_co)
         reload(reloadmodule)
         self.failUnless(hasattr(reloadmodule,'reloaded'))
+        
+        import hooktestpackage.oldabs
+        self.assertEqual(hooktestpackage.oldabs.get_name(),
+                         "hooktestpackage.oldabs")
+        self.assertEqual(hooktestpackage.oldabs.sub,
+                         hooktestpackage.sub)
+
+        import hooktestpackage.newrel
+        self.assertEqual(hooktestpackage.newrel.get_name(),
+                         "hooktestpackage.newrel")
+        self.assertEqual(hooktestpackage.newrel.sub,
+                         hooktestpackage.sub)
+
+        import hooktestpackage.futrel
+        self.assertEqual(hooktestpackage.futrel.get_name(),
+                         "hooktestpackage.futrel")
+        self.assertEqual(hooktestpackage.futrel.sub,
+                         hooktestpackage.sub)
+        
+        import sub
+        self.assertEqual(sub.get_name(), "sub")
+
+        import hooktestpackage.newabs
+        self.assertEqual(hooktestpackage.newabs.get_name(),
+                         "hooktestpackage.newabs")
+        self.assertEqual(hooktestpackage.newabs.sub, sub)
 
     def testMetaPath(self):
         i = MetaImporter()