gh-126139: Improve error message location for future statement with unknown feature

Lib/test/test_exceptions.py

@@ -319,8 +319,8 @@ def baz():
         check('def f():\n  global x\n  nonlocal x', 2, 3)
 
         # Errors thrown by future.c
-        check('from __future__ import doesnt_exist', 1, 1)
-        check('from __future__ import braces', 1, 1)
+        check('from __future__ import doesnt_exist', 1, 24)
+        check('from __future__ import braces', 1, 24)
         check('x=1\nfrom __future__ import division', 2, 1)
         check('foo(1=2)', 1, 5)
         check('def f():\n  x, y: int', 2, 3)

Lib/test/test_future_stmt/test_future.py

@@ -88,7 +88,7 @@ def test_unknown_future_flag(self):
         """
         self.assertSyntaxError(
             code, lineno=2,
-            message='future feature rested_snopes is not defined',
+            message='future feature rested_snopes is not defined', offset=24,
         )
 
     def test_future_import_not_on_top(self):
@@ -137,19 +137,19 @@ def test_future_import_star(self):
         code = """
             from __future__ import *
         """
-        self.assertSyntaxError(code, message='future feature * is not defined')
+        self.assertSyntaxError(code, message='future feature * is not defined', offset=24)
 
     def test_future_import_braces(self):
         code = """
             from __future__ import braces
         """
         # Congrats, you found an easter egg!
-        self.assertSyntaxError(code, message='not a chance')
+        self.assertSyntaxError(code, message='not a chance', offset=24)
 
         code = """
             from __future__ import nested_scopes, braces
         """
-        self.assertSyntaxError(code, message='not a chance')
+        self.assertSyntaxError(code, message='not a chance', offset=39)
 
     def test_module_with_future_import_not_on_top(self):
         with self.assertRaises(SyntaxError) as cm:

Misc/NEWS.d/next/Core_and_Builtins/2024-10-29-15-17-31.gh-issue-126139.B4OQ8a.rst

@@ -0,0 +1,2 @@
+Provide better error location when attempting to use a :term:`future
+statement <__future__>` with an unknown future feature.

Python/future.c

@@ -41,12 +41,20 @@ future_check_features(_PyFutureFeatures *ff, stmt_ty s, PyObject *filename)
         } else if (strcmp(feature, "braces") == 0) {
             PyErr_SetString(PyExc_SyntaxError,
                             "not a chance");
-            PyErr_SyntaxLocationObject(filename, s->lineno, s->col_offset + 1);
+            PyErr_RangedSyntaxLocationObject(filename,
+                                             name->lineno,
+                                             name->col_offset + 1,
+                                             name->end_lineno,
+                                             name->end_col_offset + 1);
             return 0;
         } else {
             PyErr_Format(PyExc_SyntaxError,
                          UNDEFINED_FUTURE_FEATURE, feature);
-            PyErr_SyntaxLocationObject(filename, s->lineno, s->col_offset + 1);
+            PyErr_RangedSyntaxLocationObject(filename,
+                                             name->lineno,
+                                             name->col_offset + 1,
+                                             name->end_lineno,
+                                             name->end_col_offset + 1);
             return 0;
         }
     }