gh-122145: Handle an empty AST body when reporting tracebacks.

Lib/test/test_traceback.py

@@ -3275,6 +3275,17 @@ def format_frame_summary(self, frame_summary, colorize=False):
             f'  File "{__file__}", line {lno}, in f\n    1/0\n'
         )
 
+    def test_traceback_empty_ast(self):
+        # see gh-122145
+        fs = traceback.FrameSummary("?", 1, "s", lookup_line=False,
+                                    locals=None, end_lineno=1, colno=0,
+                                    end_colno=10, line="#123456789")
+        self.assertListEqual(
+            traceback.StackSummary().format_frame_summary(fs).splitlines(),
+            ['  File "?", line 1, in s', '    #123456789']
+        )
+
+
 class Unrepresentable:
     def __repr__(self) -> str:
         raise Exception("Unrepresentable")

Lib/traceback.py

@@ -698,6 +698,8 @@ def _should_show_carets(self, start_offset, end_offset, all_lines, anchors):
         with suppress(SyntaxError, ImportError):
             import ast
             tree = ast.parse('\n'.join(all_lines))
+            if not tree.body:
+                return False
             statement = tree.body[0]
             value = None
             def _spawns_full_line(value):

Misc/NEWS.d/next/Library/2024-07-23-12-38-14.gh-issue-122145.sTO8nX.rst

@@ -0,0 +1,2 @@
+Fix an issue when reporting tracebacks containing only Python comments.
+Patch by Bénédikt Tran.