when no module is given in a 'from' relative import, make ImportFrom.module NULL

benjaminp · benjaminp · commit 4af7e21e611e · 2009-06-13T20:23:33.000Z
diff --git a/Lib/test/test_ast.py b/Lib/test/test_ast.py
@@ -152,6 +152,10 @@ def test_slice(self):
         self.assertIsNone(slc.lower)
         self.assertIsNone(slc.step)
 
+    def test_from_import(self):
+        im = ast.parse("from . import y").body[0]
+        self.assertIsNone(im.module)
+
     def test_nodeclasses(self):
         x = ast.BinOp(1, 2, 3, lineno=0)
         self.assertEquals(x.left, 1)
diff --git a/Misc/NEWS b/Misc/NEWS
@@ -12,6 +12,9 @@ What's New in Python 2.7 alpha 1
 Core and Builtins
 -----------------
 
+- When no module is given in a relative import, the module field of the
+  ImportFrom AST node is now None instead of an empty string.
+
 - Assignment to None using import statements now raises a SyntaxError.
 
 - In the slice AST type, the step field will always be None if a step expression
diff --git a/Parser/Python.asdl b/Parser/Python.asdl
@@ -34,7 +34,7 @@ module Python version "$Revision$"
 	      | Assert(expr test, expr? msg)
 
 	      | Import(alias* names)
-	      | ImportFrom(identifier module, alias* names, int? level)
+	      | ImportFrom(identifier? module, alias* names, int? level)
 
 	      -- Doesn't capture requirement that locals must be
 	      -- defined if globals is
diff --git a/Python/Python-ast.c b/Python/Python-ast.c
@@ -1330,11 +1330,6 @@ ImportFrom(identifier module, asdl_seq * names, int level, int lineno, int
            col_offset, PyArena *arena)
 {
         stmt_ty p;
-        if (!module) {
-                PyErr_SetString(PyExc_ValueError,
-                                "field module is required for ImportFrom");
-                return NULL;
-        }
         p = (stmt_ty)PyArena_Malloc(arena, sizeof(*p));
         if (!p)
                 return NULL;
@@ -4273,8 +4268,7 @@ obj2ast_stmt(PyObject* obj, stmt_ty* out, PyArena* arena)
                         Py_XDECREF(tmp);
                         tmp = NULL;
                 } else {
-                        PyErr_SetString(PyExc_TypeError, "required field \"module\" missing from ImportFrom");
-                        return 1;
+                        module = NULL;
                 }
                 if (PyObject_HasAttrString(obj, "names")) {
                         int res;
diff --git a/Python/ast.c b/Python/ast.c
@@ -2440,7 +2440,7 @@ ast_for_import_stmt(struct compiling *c, const node *n)
         int n_children;
         int idx, ndots = 0;
         alias_ty mod = NULL;
-        identifier modname;
+        identifier modname = NULL;
         
        /* Count the number of dots (for relative imports) and check for the
           optional module name */
@@ -2504,8 +2504,6 @@ ast_for_import_stmt(struct compiling *c, const node *n)
         }
         if (mod != NULL)
             modname = mod->name;
-        else
-            modname = new_identifier("", c->c_arena);
         return ImportFrom(modname, aliases, ndots, lineno, col_offset,
                           c->c_arena);
     }
diff --git a/Python/compile.c b/Python/compile.c
@@ -1976,6 +1976,13 @@ compiler_from_import(struct compiler *c, stmt_ty s)
 
 	PyObject *names = PyTuple_New(n);
 	PyObject *level;
+	static PyObject *empty_string;
+
+	if (!empty_string) {
+		empty_string = PyString_FromString("");
+		if (!empty_string)
+			return 0;
+	}
 	
 	if (!names)
 		return 0;
@@ -1998,23 +2005,24 @@ compiler_from_import(struct compiler *c, stmt_ty s)
 		PyTuple_SET_ITEM(names, i, alias->name);
 	}
 
-	if (s->lineno > c->c_future->ff_lineno) {
-		if (!strcmp(PyString_AS_STRING(s->v.ImportFrom.module),
-			    "__future__")) {
-			Py_DECREF(level);
-			Py_DECREF(names);
-			return compiler_error(c, 
-				      "from __future__ imports must occur "
+	if (s->lineno > c->c_future->ff_lineno && s->v.ImportFrom.module && 
+	    !strcmp(PyString_AS_STRING(s->v.ImportFrom.module), "__future__")) {
+		Py_DECREF(level);
+		Py_DECREF(names);
+		return compiler_error(c, "from __future__ imports must occur "
 				      "at the beginning of the file");
-
-		}
 	}
 
 	ADDOP_O(c, LOAD_CONST, level, consts);
 	Py_DECREF(level);
 	ADDOP_O(c, LOAD_CONST, names, consts);
 	Py_DECREF(names);
-	ADDOP_NAME(c, IMPORT_NAME, s->v.ImportFrom.module, names);
+	if (s->v.ImportFrom.module) {
+		ADDOP_NAME(c, IMPORT_NAME, s->v.ImportFrom.module, names);
+	}
+	else {
+		ADDOP_NAME(c, IMPORT_NAME, empty_string, names);
+	}
 	for (i = 0; i < n; i++) {
 		alias_ty alias = (alias_ty)asdl_seq_GET(s->v.ImportFrom.names, i);
 		identifier store_name;
