bpo-39579: Fix Attribute end_col_offset to point at the current node (GH-18405)

Lib/test/test_ast.py

@@ -142,6 +142,8 @@ exec_tests = [
     "@deco1\n@deco2()\n@deco3(1)\nclass C: pass",
     # Decorator with generator argument
     "@deco(a for a in b)\ndef f(): pass",
+    # Decorator with attribute
+    "@a.b.c\ndef f(): pass",
     # Simple assignment expression
     "(a := 1)",
     # Positional-only arguments
@@ -616,6 +618,11 @@ class AST_Tests(unittest.TestCase):
         self.assertEqual(grandchild_binop.end_col_offset, 3)
         self.assertEqual(grandchild_binop.end_lineno, 1)
 
+    def test_issue39579_dotted_name_end_col_offset(self):
+        tree = ast.parse('@a.b.c\ndef f(): pass')
+        attr_b = tree.body[0].decorator_list[0].value
+        self.assertEqual(attr_b.end_col_offset, 4)
+
 class ASTHelpers_Test(unittest.TestCase):
     maxDiff = None
 
@@ -1903,6 +1910,7 @@ exec_results = [
 ('Module', [('AsyncFunctionDef', (4, 0, 4, 19), 'f', ('arguments', [], [], None, [], [], None, []), [('Pass', (4, 15, 4, 19))], [('Name', (1, 1, 1, 6), 'deco1', ('Load',)), ('Call', (2, 1, 2, 8), ('Name', (2, 1, 2, 6), 'deco2', ('Load',)), [], []), ('Call', (3, 1, 3, 9), ('Name', (3, 1, 3, 6), 'deco3', ('Load',)), [('Constant', (3, 7, 3, 8), 1, None)], [])], None, None)], []),
 ('Module', [('ClassDef', (4, 0, 4, 13), 'C', [], [], [('Pass', (4, 9, 4, 13))], [('Name', (1, 1, 1, 6), 'deco1', ('Load',)), ('Call', (2, 1, 2, 8), ('Name', (2, 1, 2, 6), 'deco2', ('Load',)), [], []), ('Call', (3, 1, 3, 9), ('Name', (3, 1, 3, 6), 'deco3', ('Load',)), [('Constant', (3, 7, 3, 8), 1, None)], [])])], []),
 ('Module', [('FunctionDef', (2, 0, 2, 13), 'f', ('arguments', [], [], None, [], [], None, []), [('Pass', (2, 9, 2, 13))], [('Call', (1, 1, 1, 19), ('Name', (1, 1, 1, 5), 'deco', ('Load',)), [('GeneratorExp', (1, 5, 1, 19), ('Name', (1, 6, 1, 7), 'a', ('Load',)), [('comprehension', ('Name', (1, 12, 1, 13), 'a', ('Store',)), ('Name', (1, 17, 1, 18), 'b', ('Load',)), [], 0)])], [])], None, None)], []),
+('Module', [('FunctionDef', (2, 0, 2, 13), 'f', ('arguments', [], [], None, [], [], None, []), [('Pass', (2, 9, 2, 13))], [('Attribute', (1, 1, 1, 6), ('Attribute', (1, 1, 1, 4), ('Name', (1, 1, 1, 2), 'a', ('Load',)), 'b', ('Load',)), 'c', ('Load',))], None, None)], []),
 ('Module', [('Expr', (1, 0, 1, 8), ('NamedExpr', (1, 1, 1, 7), ('Name', (1, 1, 1, 2), 'a', ('Store',)), ('Constant', (1, 6, 1, 7), 1, None)))], []),
 ('Module', [('FunctionDef', (1, 0, 1, 18), 'f', ('arguments', [('arg', (1, 6, 1, 7), 'a', None, None)], [], None, [], [], None, []), [('Pass', (1, 14, 1, 18))], [], None, None)], []),
 ('Module', [('FunctionDef', (1, 0, 1, 26), 'f', ('arguments', [('arg', (1, 6, 1, 7), 'a', None, None)], [('arg', (1, 12, 1, 13), 'c', None, None), ('arg', (1, 15, 1, 16), 'd', None, None), ('arg', (1, 18, 1, 19), 'e', None, None)], None, [], [], None, []), [('Pass', (1, 22, 1, 26))], [], None, None)], []),

Misc/NEWS.d/next/Core and Builtins/2020-02-07-15-18-35.bpo-39579.itNmC0.rst

@@ -0,0 +1 @@
+Change the ending column offset of `Attribute` nodes constructed in `ast_for_dotted_name` to point at the end of the current node and not at the end of the last `NAME` node.

Python/ast.c

@@ -1715,11 +1715,12 @@ ast_for_dotted_name(struct compiling *c, const node *n)
         return NULL;
 
     for (i = 2; i < NCH(n); i+=2) {
-        id = NEW_IDENTIFIER(CHILD(n, i));
+        const node *child = CHILD(n, i);
+        id = NEW_IDENTIFIER(child);
         if (!id)
             return NULL;
         e = Attribute(e, id, Load, lineno, col_offset,
-                      n->n_end_lineno, n->n_end_col_offset, c->c_arena);
+                      child->n_end_lineno, child->n_end_col_offset, c->c_arena);
         if (!e)
             return NULL;
     }