python · matanagasauce · Apr 6, 2020 · Apr 7, 2020 · Apr 7, 2020
diff --git a/Lib/test/test_ast.py b/Lib/test/test_ast.py
@@ -645,6 +645,21 @@ def test_issue39579_dotted_name_end_col_offset(self):
        attr_b = tree.body[0].decorator_list[0].value
        self.assertEqual(attr_b.end_col_offset, 4)

+    def test_issue35212_fstring_col_offset(self):
+        tree = ast.parse(dedent('''
+            (
+                f"""Some multi-line text.
+                    {a:b}
+                It goes on..."""
+            )
+        ''').strip())
+        fstr = tree.body[0].value
+        value = fstr.values[1].value
+        self.assertEqual(value.col_offset, 9)
+        self.assertEqual(value.lineno, 3)
+        self.assertEqual(value.end_col_offset, 10)
+        self.assertEqual(value.end_lineno, 3)
+
    def test_ast_asdl_signature(self):
        self.assertEqual(ast.withitem.__doc__, "withitem(expr context_expr, expr? optional_vars)")
        self.assertEqual(ast.GtE.__doc__, "GtE")

diff --git a/Lib/test/test_fstring.py b/Lib/test/test_fstring.py
@@ -324,8 +324,8 @@ def test_ast_line_numbers_multiline_fstring(self):
        self.assertEqual(binop.lineno, 4)
        self.assertEqual(binop.left.lineno, 4)
        self.assertEqual(binop.right.lineno, 6)
-        self.assertEqual(binop.col_offset, 4)
-        self.assertEqual(binop.left.col_offset, 4)
+        self.assertEqual(binop.col_offset, 3)
+        self.assertEqual(binop.left.col_offset, 3)
        self.assertEqual(binop.right.col_offset, 7)

    def test_docstring(self):

diff --git a/Misc/NEWS.d/next/Core and Builtins/2020-04-07-06-00-20.bpo-35212.86avLy.rst b/Misc/NEWS.d/next/Core and Builtins/2020-04-07-06-00-20.bpo-35212.86avLy.rst
@@ -0,0 +1 @@
+fix col_offset in f-strings
@@ -4695,8 +4695,12 @@ fstring_fix_node_location(const node *parent, node *n, char *expr_str)
        if (substr) {
            start = substr;
            while (start > parent->n_str) {
-                if (start[0] == '\n')
+                if (start[0] == '\n') {
+                    /* when the f-string expression is on a new line, clear
+                       old offset and also don't count the `\n` */
+                    cols = -1;
                    break;
+                }
                start--;
            }
            cols += (int)(substr - start);
@@ -4770,7 +4774,9 @@ fstring_compile_expr(const char *expr_start, const char *expr_end,
    }
    /* Reuse str to find the correct column offset. */
    str[0] = '{';
-    str[len+1] = '}';
+    /* bpo-35212: if the fstring has a format_spec, it doesn't match a close
+       brace. */
+    str[len+1] = 0;
    fstring_fix_node_location(n, mod_n, str);
    mod = PyAST_FromNode(mod_n, &cf, "<fstring>", c->c_arena);
    PyMem_RawFree(str);