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.

5 files changed, 14 insertions, 3 deletions

diff --git a/Include/Python-ast.h b/Include/Python-ast.h
index 3c5677c..7aef19b 100644
--- a/Include/Python-ast.h
+++ b/Include/Python-ast.h
@@ -159,6 +159,7 @@ struct _stmt {
                 struct {
                         identifier module;
                         asdl_seq *names;
+                        int level;
                 } ImportFrom;
                 
                 struct {
@@ -371,8 +372,8 @@ stmt_ty TryFinally(asdl_seq * body, asdl_seq * finalbody, int lineno, PyArena
                    *arena);
 stmt_ty Assert(expr_ty test, expr_ty msg, int lineno, PyArena *arena);
 stmt_ty Import(asdl_seq * names, int lineno, PyArena *arena);
-stmt_ty ImportFrom(identifier module, asdl_seq * names, int lineno, PyArena
-                   *arena);
+stmt_ty ImportFrom(identifier module, asdl_seq * names, int level, int lineno,
+                   PyArena *arena);
 stmt_ty Exec(expr_ty body, expr_ty globals, expr_ty locals, int lineno, PyArena
              *arena);
 stmt_ty Global(asdl_seq * names, int lineno, PyArena *arena);
diff --git a/Include/code.h b/Include/code.h
index 7dd13fe..e81b576 100644
--- a/Include/code.h
+++ b/Include/code.h
@@ -45,6 +45,7 @@ typedef struct {
 #define CO_GENERATOR_ALLOWED    0x1000
 #endif
 #define CO_FUTURE_DIVISION    	0x2000
+#define CO_FUTURE_ABSIMPORT	0x4000 /* absolute import by default */
 
 #define CO_MAXBLOCKS 20 /* Max static block nesting within a function */
 
diff --git a/Include/compile.h b/Include/compile.h
index 029cb17..66b445e 100644
--- a/Include/compile.h
+++ b/Include/compile.h
@@ -22,6 +22,7 @@ typedef struct {
 #define FUTURE_NESTED_SCOPES "nested_scopes"
 #define FUTURE_GENERATORS "generators"
 #define FUTURE_DIVISION "division"
+#define FUTURE_ABSIMPORT "absolute_import"
 
 struct _mod; /* Declare the existence of this type */
 PyAPI_FUNC(PyCodeObject *) PyAST_Compile(struct _mod *, const char *,
diff --git a/Include/import.h b/Include/import.h
index 45cc6c9..a4e5c0e 100644
--- a/Include/import.h
+++ b/Include/import.h
@@ -14,8 +14,16 @@ PyAPI_FUNC(PyObject *) PyImport_ExecCodeModuleEx(
 PyAPI_FUNC(PyObject *) PyImport_GetModuleDict(void);
 PyAPI_FUNC(PyObject *) PyImport_AddModule(const char *name);
 PyAPI_FUNC(PyObject *) PyImport_ImportModule(const char *name);
+PyAPI_FUNC(PyObject *) PyImport_ImportModuleLevel(char *name,
+	PyObject *globals, PyObject *locals, PyObject *fromlist, int level);
+
+/* For DLL compatibility */
+#undef PyImport_ImportModuleEx
 PyAPI_FUNC(PyObject *) PyImport_ImportModuleEx(
 	char *name, PyObject *globals, PyObject *locals, PyObject *fromlist);
+#define PyImport_ImportModuleEx(n, g, l, f) \
+	PyImport_ImportModuleLevel(n, g, l, f, -1);
+
 PyAPI_FUNC(PyObject *) PyImport_Import(PyObject *name);
 PyAPI_FUNC(PyObject *) PyImport_ReloadModule(PyObject *m);
 PyAPI_FUNC(void) PyImport_Cleanup(void);
diff --git a/Include/pythonrun.h b/Include/pythonrun.h
index a18a4e2..5949d5b 100644
--- a/Include/pythonrun.h
+++ b/Include/pythonrun.h
@@ -7,7 +7,7 @@
 extern "C" {
 #endif
 
-#define PyCF_MASK (CO_FUTURE_DIVISION)
+#define PyCF_MASK (CO_FUTURE_DIVISION | CO_FUTURE_ABSIMPORT)
 #define PyCF_MASK_OBSOLETE (CO_NESTED)
 #define PyCF_SOURCE_IS_UTF8  0x0100
 #define PyCF_DONT_IMPLY_DEDENT 0x0200