gh-93883: elide traceback indicators when possible (#93994)

* gh-93883: elide traceback indicators when possible

Elide traceback column indicators when the entire line of the
frame is implicated.  This reduces traceback length and draws
even more attention to the remaining (very relevant) indicators.

Example:
```
Traceback (most recent call last):
  File "query.py", line 99, in <module>
    bar()
  File "query.py", line 66, in bar
    foo()
  File "query.py", line 37, in foo
    magic_arithmetic('foo')
  File "query.py", line 18, in magic_arithmetic
    return add_counts(x) / 25
           ^^^^^^^^^^^^^
  File "query.py", line 24, in add_counts
    return 25 + query_user(user1) + query_user(user2)
                ^^^^^^^^^^^^^^^^^
  File "query.py", line 32, in query_user
    return 1 + query_count(db, response['a']['b']['c']['user'], retry=True)
                               ~~~~~~~~~~~~~~~~~~^^^^^
TypeError: 'NoneType' object is not subscriptable
```

Rather than going out of our way to provide indicator coverage
in every traceback test suite, the indicator test suite should
be responible for sufficient coverage (e.g. by adding a basic
exception group test to ensure that margin strings are covered).

Doc/library/traceback.rst

@@ -464,32 +464,27 @@ The output for the example would look similar to this:
    *** print_tb:
      File "<doctest...>", line 10, in <module>
        lumberjack()
-       ^^^^^^^^^^^^
    *** print_exception:
    Traceback (most recent call last):
      File "<doctest...>", line 10, in <module>
        lumberjack()
-       ^^^^^^^^^^^^
      File "<doctest...>", line 4, in lumberjack
        bright_side_of_death()
-       ^^^^^^^^^^^^^^^^^^^^^^
    IndexError: tuple index out of range
    *** print_exc:
    Traceback (most recent call last):
      File "<doctest...>", line 10, in <module>
        lumberjack()
-       ^^^^^^^^^^^^
      File "<doctest...>", line 4, in lumberjack
        bright_side_of_death()
-       ^^^^^^^^^^^^^^^^^^^^^^
    IndexError: tuple index out of range
    *** format_exc, first and last line:
    Traceback (most recent call last):
    IndexError: tuple index out of range
    *** format_exception:
    ['Traceback (most recent call last):\n',
-    '  File "<doctest default[0]>", line 10, in <module>\n    lumberjack()\n    ^^^^^^^^^^^^\n',
+    '  File "<doctest default[0]>", line 10, in <module>\n    lumberjack()\n',
-    '  File "<doctest default[0]>", line 4, in lumberjack\n    bright_side_of_death()\n    ^^^^^^^^^^^^^^^^^^^^^^\n',
+    '  File "<doctest default[0]>", line 4, in lumberjack\n    bright_side_of_death()\n',
     '  File "<doctest default[0]>", line 7, in bright_side_of_death\n    return tuple()[0]\n           ~~~~~~~^^^\n',
     'IndexError: tuple index out of range\n']
    *** extract_tb:
@@ -497,8 +492,8 @@ The output for the example would look similar to this:
     <FrameSummary file <doctest...>, line 4 in lumberjack>,
     <FrameSummary file <doctest...>, line 7 in bright_side_of_death>]
    *** format_tb:
-   ['  File "<doctest default[0]>", line 10, in <module>\n    lumberjack()\n    ^^^^^^^^^^^^\n',
+   ['  File "<doctest default[0]>", line 10, in <module>\n    lumberjack()\n',
-    '  File "<doctest default[0]>", line 4, in lumberjack\n    bright_side_of_death()\n    ^^^^^^^^^^^^^^^^^^^^^^\n',
+    '  File "<doctest default[0]>", line 4, in lumberjack\n    bright_side_of_death()\n',
     '  File "<doctest default[0]>", line 7, in bright_side_of_death\n    return tuple()[0]\n           ~~~~~~~^^^\n']
    *** tb_lineno: 10
 

Doc/whatsnew/3.11.rst

@@ -117,7 +117,6 @@ when dealing with deeply nested dictionary objects and multiple function calls,
     Traceback (most recent call last):
       File "query.py", line 37, in <module>
         magic_arithmetic('foo')
-        ^^^^^^^^^^^^^^^^^^^^^^^
       File "query.py", line 18, in magic_arithmetic
         return add_counts(x) / 25
                ^^^^^^^^^^^^^

Lib/idlelib/idle_test/test_run.py

@@ -3,7 +3,7 @@
 from idlelib import run
 import io
 import sys
-from test.support import captured_output, captured_stderr, has_no_debug_ranges
+from test.support import captured_output, captured_stderr
 import unittest
 from unittest import mock
 import idlelib
@@ -33,14 +33,9 @@ def __eq__(self, other):
                         run.print_exception()
 
         tb = output.getvalue().strip().splitlines()
-        if has_no_debug_ranges():
+        self.assertEqual(11, len(tb))
-            self.assertEqual(11, len(tb))
+        self.assertIn('UnhashableException: ex2', tb[3])
-            self.assertIn('UnhashableException: ex2', tb[3])
+        self.assertIn('UnhashableException: ex1', tb[10])
-            self.assertIn('UnhashableException: ex1', tb[10])
-        else:
-            self.assertEqual(13, len(tb))
-            self.assertIn('UnhashableException: ex2', tb[4])
-            self.assertIn('UnhashableException: ex1', tb[12])
 
     data = (('1/0', ZeroDivisionError, "division by zero\n"),
             ('abc', NameError, "name 'abc' is not defined. "

Lib/test/test_cmd_line_script.py

@@ -549,10 +549,10 @@ def test_pep_409_verbiage(self):
             script_name = _make_test_script(script_dir, 'script', script)
             exitcode, stdout, stderr = assert_python_failure(script_name)
             text = stderr.decode('ascii').split('\n')
-            self.assertEqual(len(text), 6)
+            self.assertEqual(len(text), 5)
             self.assertTrue(text[0].startswith('Traceback'))
             self.assertTrue(text[1].startswith('  File '))
-            self.assertTrue(text[4].startswith('NameError'))
+            self.assertTrue(text[3].startswith('NameError'))
 
     def test_non_ascii(self):
         # Mac OS X denies the creation of a file with an invalid UTF-8 name.

Lib/test/test_doctest.py

@@ -2854,7 +2854,7 @@ def test_testmod(): r"""
     # Skip the test: the filesystem encoding is unable to encode the filename
     supports_unicode = False
 
-if supports_unicode and not support.has_no_debug_ranges():
+if supports_unicode:
     def test_unicode(): """
 Check doctest with a non-ascii filename:
 
@@ -2876,10 +2876,8 @@ def test_unicode(): """
         Traceback (most recent call last):
           File ...
             exec(compile(example.source, filename, "single",
-            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
           File "<doctest foo-bär@baz[0]>", line 1, in <module>
             raise Exception('clé')
-            ^^^^^^^^^^^^^^^^^^^^^^
         Exception: clé
     TestResults(failed=1, attempted=1)
     """

Lib/test/test_traceback.py

@@ -252,7 +252,7 @@ def do_test(firstlines, message, charset, lineno):
             self.assertTrue(stdout[2].endswith(err_line),
                 "Invalid traceback line: {0!r} instead of {1!r}".format(
                     stdout[2], err_line))
-            actual_err_msg = stdout[3 if has_no_debug_ranges() else 4]
+            actual_err_msg = stdout[3]
             self.assertTrue(actual_err_msg == err_msg,
                 "Invalid error message: {0!r} instead of {1!r}".format(
                     actual_err_msg, err_msg))
@@ -386,18 +386,19 @@ def get_exception(self, callable):
     callable_line = get_exception.__code__.co_firstlineno + 2
 
     def test_basic_caret(self):
+        # NOTE: In caret tests, "if True:" is used as a way to force indicator
+        #   display, since the raising expression spans only part of the line.
         def f():
-            raise ValueError("basic caret tests")
+            if True: raise ValueError("basic caret tests")
 
         lineno_f = f.__code__.co_firstlineno
         expected_f = (
             'Traceback (most recent call last):\n'
             f'  File "{__file__}", line {self.callable_line}, in get_exception\n'
             '    callable()\n'
-            '    ^^^^^^^^^^\n'
             f'  File "{__file__}", line {lineno_f+1}, in f\n'
-            '    raise ValueError("basic caret tests")\n'
+            '    if True: raise ValueError("basic caret tests")\n'
-            '    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\n'
+            '             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\n'
         )
         result_lines = self.get_exception(f)
         self.assertEqual(result_lines, expected_f.splitlines())
@@ -406,17 +407,16 @@ def test_line_with_unicode(self):
         # Make sure that even if a line contains multi-byte unicode characters
         # the correct carets are printed.
         def f_with_unicode():
-            raise ValueError("Ĥellö Wörld")
+            if True: raise ValueError("Ĥellö Wörld")
 
         lineno_f = f_with_unicode.__code__.co_firstlineno
         expected_f = (
             'Traceback (most recent call last):\n'
             f'  File "{__file__}", line {self.callable_line}, in get_exception\n'
             '    callable()\n'
-            '    ^^^^^^^^^^\n'
             f'  File "{__file__}", line {lineno_f+1}, in f_with_unicode\n'
-            '    raise ValueError("Ĥellö Wörld")\n'
+            '    if True: raise ValueError("Ĥellö Wörld")\n'
-            '    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\n'
+            '             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\n'
         )
         result_lines = self.get_exception(f_with_unicode)
         self.assertEqual(result_lines, expected_f.splitlines())
@@ -431,7 +431,6 @@ def foo(a: THIS_DOES_NOT_EXIST ) -> int:
             'Traceback (most recent call last):\n'
             f'  File "{__file__}", line {self.callable_line}, in get_exception\n'
             '    callable()\n'
-            '    ^^^^^^^^^^\n'
             f'  File "{__file__}", line {lineno_f+1}, in f_with_type\n'
             '    def foo(a: THIS_DOES_NOT_EXIST ) -> int:\n'
             '               ^^^^^^^^^^^^^^^^^^^\n'
@@ -443,7 +442,7 @@ def test_caret_multiline_expression(self):
         # Make sure no carets are printed for expressions spanning multiple
         # lines.
         def f_with_multiline():
-            raise ValueError(
+            if True: raise ValueError(
                 "error over multiple lines"
             )
 
@@ -452,10 +451,9 @@ def f_with_multiline():
             'Traceback (most recent call last):\n'
             f'  File "{__file__}", line {self.callable_line}, in get_exception\n'
             '    callable()\n'
-            '    ^^^^^^^^^^\n'
             f'  File "{__file__}", line {lineno_f+1}, in f_with_multiline\n'
-            '    raise ValueError(\n'
+            '    if True: raise ValueError(\n'
-            '    ^^^^^^^^^^^^^^^^^'
+            '             ^^^^^^^^^^^^^^^^^'
         )
         result_lines = self.get_exception(f_with_multiline)
         self.assertEqual(result_lines, expected_f.splitlines())
@@ -484,7 +482,6 @@ def f_with_multiline():
             'Traceback (most recent call last):\n'
             f'  File "{__file__}", line {self.callable_line}, in get_exception\n'
             '    callable()\n'
-            '    ^^^^^^^^^^\n'
             f'  File "{__file__}", line {lineno_f+2}, in f_with_multiline\n'
             '    return compile(code, "?", "exec")\n'
             '           ^^^^^^^^^^^^^^^^^^^^^^^^^^\n'
@@ -501,9 +498,8 @@ def test_caret_multiline_expression_bin_op(self):
         # lines.
         def f_with_multiline():
             return (
-                1 /
+                2 + 1 /
-                0 +
+                0
-                2
             )
 
         lineno_f = f_with_multiline.__code__.co_firstlineno
@@ -511,10 +507,9 @@ def f_with_multiline():
             'Traceback (most recent call last):\n'
             f'  File "{__file__}", line {self.callable_line}, in get_exception\n'
             '    callable()\n'
-            '    ^^^^^^^^^^\n'
             f'  File "{__file__}", line {lineno_f+2}, in f_with_multiline\n'
-            '    1 /\n'
+            '    2 + 1 /\n'
-            '    ^^^'
+            '        ^^^'
         )
         result_lines = self.get_exception(f_with_multiline)
         self.assertEqual(result_lines, expected_f.splitlines())
@@ -529,7 +524,6 @@ def f_with_binary_operator():
             'Traceback (most recent call last):\n'
             f'  File "{__file__}", line {self.callable_line}, in get_exception\n'
             '    callable()\n'
-            '    ^^^^^^^^^^\n'
             f'  File "{__file__}", line {lineno_f+2}, in f_with_binary_operator\n'
             '    return 10 + divisor / 0 + 30\n'
             '                ~~~~~~~~^~~\n'
@@ -547,7 +541,6 @@ def f_with_binary_operator():
             'Traceback (most recent call last):\n'
             f'  File "{__file__}", line {self.callable_line}, in get_exception\n'
             '    callable()\n'
-            '    ^^^^^^^^^^\n'
             f'  File "{__file__}", line {lineno_f+2}, in f_with_binary_operator\n'
             '    return 10 + divisor // 0 + 30\n'
             '                ~~~~~~~~^^~~\n'
@@ -565,7 +558,6 @@ def f_with_subscript():
             'Traceback (most recent call last):\n'
             f'  File "{__file__}", line {self.callable_line}, in get_exception\n'
             '    callable()\n'
-            '    ^^^^^^^^^^\n'
             f'  File "{__file__}", line {lineno_f+2}, in f_with_subscript\n'
             "    return some_dict['x']['y']['z']\n"
             '           ~~~~~~~~~~~~~~~~~~~^^^^^\n'
@@ -589,7 +581,6 @@ def test_traceback_specialization_with_syntax_error(self):
             'Traceback (most recent call last):\n'
             f'  File "{__file__}", line {self.callable_line}, in get_exception\n'
             '    callable()\n'
-            '    ^^^^^^^^^^\n'
             f'  File "{TESTFN}", line {lineno_f}, in <module>\n'
             "    1 $ 0 / 1 / 2\n"
             '    ^^^^^\n'
@@ -597,7 +588,7 @@ def test_traceback_specialization_with_syntax_error(self):
         self.assertEqual(result_lines, expected_error.splitlines())
 
     def test_traceback_very_long_line(self):
-        source = "a" * 256
+        source = "if True: " + "a" * 256
         bytecode = compile(source, TESTFN, "exec")
 
         with open(TESTFN, "w") as file:
@@ -612,13 +603,54 @@ def test_traceback_very_long_line(self):
             'Traceback (most recent call last):\n'
             f'  File "{__file__}", line {self.callable_line}, in get_exception\n'
             '    callable()\n'
-            '    ^^^^^^^^^^\n'
             f'  File "{TESTFN}", line {lineno_f}, in <module>\n'
             f'    {source}\n'
-            f'    {"^"*len(source)}\n'
+            f'    {" "*len("if True: ") + "^"*256}\n'
         )
         self.assertEqual(result_lines, expected_error.splitlines())
 
+    def test_secondary_caret_not_elided(self):
+        # Always show a line's indicators if they include the secondary character.
+        def f_with_subscript():
+            some_dict = {'x': {'y': None}}
+            some_dict['x']['y']['z']
+
+        lineno_f = f_with_subscript.__code__.co_firstlineno
+        expected_error = (
+            'Traceback (most recent call last):\n'
+            f'  File "{__file__}", line {self.callable_line}, in get_exception\n'
+            '    callable()\n'
+            f'  File "{__file__}", line {lineno_f+2}, in f_with_subscript\n'
+            "    some_dict['x']['y']['z']\n"
+            '    ~~~~~~~~~~~~~~~~~~~^^^^^\n'
+        )
+        result_lines = self.get_exception(f_with_subscript)
+        self.assertEqual(result_lines, expected_error.splitlines())
+
+    def test_caret_exception_group(self):
+        # Notably, this covers whether indicators handle margin strings correctly.
+        # (Exception groups use margin strings to display vertical indicators.)
+        # The implementation must account for both "indent" and "margin" offsets.
+
+        def exc():
+            if True: raise ExceptionGroup("eg", [ValueError(1), TypeError(2)])
+
+        expected_error = (
+             f'  + Exception Group Traceback (most recent call last):\n'
+             f'  |   File "{__file__}", line {self.callable_line}, in get_exception\n'
+             f'  |     callable()\n'
+             f'  |   File "{__file__}", line {exc.__code__.co_firstlineno + 1}, in exc\n'
+             f'  |     if True: raise ExceptionGroup("eg", [ValueError(1), TypeError(2)])\n'
+             f'  |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\n'
+             f'  | ExceptionGroup: eg (2 sub-exceptions)\n'
+             f'  +-+---------------- 1 ----------------\n'
+             f'    | ValueError: 1\n'
+             f'    +---------------- 2 ----------------\n'
+             f'    | TypeError: 2\n')
+
+        result_lines = self.get_exception(exc)
+        self.assertEqual(result_lines, expected_error.splitlines())
+
     def assertSpecialized(self, func, expected_specialization):
         result_lines = self.get_exception(func)
         specialization_line = result_lines[-1]
@@ -672,13 +704,11 @@ def g(): pass
             'Traceback (most recent call last):\n'
             f'  File "{__file__}", line {self.callable_line}, in get_exception\n'
             '    callable()\n'
-            '    ^^^^^^^^^^\n'
             f'  File "{__file__}", line {lineno_applydescs + 1}, in applydecs\n'
             '    @dec_error\n'
             '     ^^^^^^^^^\n'
             f'  File "{__file__}", line {lineno_dec_error + 1}, in dec_error\n'
             '    raise TypeError\n'
-            '    ^^^^^^^^^^^^^^^\n'
         )
         self.assertEqual(result_lines, expected_error.splitlines())
 
@@ -692,13 +722,11 @@ class A: pass
             'Traceback (most recent call last):\n'
             f'  File "{__file__}", line {self.callable_line}, in get_exception\n'
             '    callable()\n'
-            '    ^^^^^^^^^^\n'
             f'  File "{__file__}", line {lineno_applydescs_class + 1}, in applydecs_class\n'
             '    @dec_error\n'
             '     ^^^^^^^^^\n'
             f'  File "{__file__}", line {lineno_dec_error + 1}, in dec_error\n'
             '    raise TypeError\n'
-            '    ^^^^^^^^^^^^^^^\n'
         )
         self.assertEqual(result_lines, expected_error.splitlines())
 
@@ -816,12 +844,8 @@ def check_traceback_format(self, cleanup_func=None):
         # Make sure that the traceback is properly indented.
         tb_lines = python_fmt.splitlines()
         banner = tb_lines[0]
-        if has_no_debug_ranges():
+        self.assertEqual(len(tb_lines), 5)
-            self.assertEqual(len(tb_lines), 5)
+        location, source_line = tb_lines[-2], tb_lines[-1]
-            location, source_line = tb_lines[-2], tb_lines[-1]
-        else:
-            self.assertEqual(len(tb_lines), 7)
-            location, source_line = tb_lines[-3], tb_lines[-2]
         self.assertTrue(banner.startswith('Traceback'))
         self.assertTrue(location.startswith('  File'))
         self.assertTrue(source_line.startswith('    raise'))
@@ -885,16 +909,12 @@ def f():
             'Traceback (most recent call last):\n'
             f'  File "{__file__}", line {lineno_f+5}, in _check_recursive_traceback_display\n'
             '    f()\n'
-            '    ^^^\n'
             f'  File "{__file__}", line {lineno_f+1}, in f\n'
             '    f()\n'
-            '    ^^^\n'
             f'  File "{__file__}", line {lineno_f+1}, in f\n'
             '    f()\n'
-            '    ^^^\n'
             f'  File "{__file__}", line {lineno_f+1}, in f\n'
             '    f()\n'
-            '    ^^^\n'
             # XXX: The following line changes depending on whether the tests
             # are run through the interactive interpreter or with -m
             # It also varies depending on the platform (stack size)
@@ -945,14 +965,12 @@ def g(count=10):
             '  [Previous line repeated 7 more times]\n'
             f'  File "{__file__}", line {lineno_g+3}, in g\n'
             '    raise ValueError\n'
-            '    ^^^^^^^^^^^^^^^^\n'
             'ValueError\n'
         )
         tb_line = (
             'Traceback (most recent call last):\n'
             f'  File "{__file__}", line {lineno_g+7}, in _check_recursive_traceback_display\n'
             '    g()\n'
-            '    ^^^\n'
         )
         expected = (tb_line + result_g).splitlines()
         actual = stderr_g.getvalue().splitlines()
@@ -977,7 +995,6 @@ def h(count=10):
             'Traceback (most recent call last):\n'
             f'  File "{__file__}", line {lineno_h+7}, in _check_recursive_traceback_display\n'
             '    h()\n'
-            '    ^^^\n'
             f'  File "{__file__}", line {lineno_h+2}, in h\n'
             '    return h(count-1)\n'
             '           ^^^^^^^^^^\n'
@@ -990,7 +1007,6 @@ def h(count=10):
             '  [Previous line repeated 7 more times]\n'
             f'  File "{__file__}", line {lineno_h+3}, in h\n'
             '    g()\n'
-            '    ^^^\n'
         )
         expected = (result_h + result_g).splitlines()
         actual = stderr_h.getvalue().splitlines()
@@ -1016,14 +1032,12 @@ def h(count=10):
             '           ^^^^^^^^^^\n'
             f'  File "{__file__}", line {lineno_g+3}, in g\n'
             '    raise ValueError\n'
-            '    ^^^^^^^^^^^^^^^^\n'
             'ValueError\n'
         )
         tb_line = (
             'Traceback (most recent call last):\n'
-            f'  File "{__file__}", line {lineno_g+81}, in _check_recursive_traceback_display\n'
+            f'  File "{__file__}", line {lineno_g+77}, in _check_recursive_traceback_display\n'
             '    g(traceback._RECURSIVE_CUTOFF)\n'
-            '    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\n'
         )
         expected = (tb_line + result_g).splitlines()
         actual = stderr_g.getvalue().splitlines()
@@ -1050,14 +1064,12 @@ def h(count=10):
             '  [Previous line repeated 1 more time]\n'
             f'  File "{__file__}", line {lineno_g+3}, in g\n'
             '    raise ValueError\n'
-            '    ^^^^^^^^^^^^^^^^\n'
             'ValueError\n'
         )
         tb_line = (
             'Traceback (most recent call last):\n'
-            f'  File "{__file__}", line {lineno_g+114}, in _check_recursive_traceback_display\n'
+            f'  File "{__file__}", line {lineno_g+108}, in _check_recursive_traceback_display\n'
             '    g(traceback._RECURSIVE_CUTOFF + 1)\n'
-            '    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\n'
         )
         expected = (tb_line + result_g).splitlines()
         actual = stderr_g.getvalue().splitlines()
@@ -1110,16 +1122,10 @@ def __eq__(self, other):
             exception_print(exc_val)
 
         tb = stderr_f.getvalue().strip().splitlines()
-        if has_no_debug_ranges():
+        self.assertEqual(11, len(tb))
-            self.assertEqual(11, len(tb))
+        self.assertEqual(context_message.strip(), tb[5])
-            self.assertEqual(context_message.strip(), tb[5])
+        self.assertIn('UnhashableException: ex2', tb[3])
-            self.assertIn('UnhashableException: ex2', tb[3])
+        self.assertIn('UnhashableException: ex1', tb[10])
-            self.assertIn('UnhashableException: ex1', tb[10])
-        else:
-            self.assertEqual(13, len(tb))
-            self.assertEqual(context_message.strip(), tb[6])
-            self.assertIn('UnhashableException: ex2', tb[4])
-            self.assertIn('UnhashableException: ex1', tb[12])
 
     def deep_eg(self):
         e = TypeError(1)
@@ -1255,12 +1261,8 @@ def test_context_suppression(self):
         except ZeroDivisionError as _:
             e = _
         lines = self.get_report(e).splitlines()
-        if has_no_debug_ranges():
+        self.assertEqual(len(lines), 4)
-            self.assertEqual(len(lines), 4)
+        self.assertTrue(lines[3].startswith('ZeroDivisionError'))
-            self.assertTrue(lines[3].startswith('ZeroDivisionError'))
-        else:
-            self.assertEqual(len(lines), 5)
-            self.assertTrue(lines[4].startswith('ZeroDivisionError'))
         self.assertTrue(lines[0].startswith('Traceback'))
         self.assertTrue(lines[1].startswith('  File'))
         self.assertIn('ZeroDivisionError from None', lines[2])
@@ -1510,10 +1512,8 @@ def exc():
              f'  + Exception Group Traceback (most recent call last):\n'
              f'  |   File "{__file__}", line {self.callable_line}, in get_exception\n'
              f'  |     exception_or_callable()\n'
-             f'  |     ^^^^^^^^^^^^^^^^^^^^^^^\n'
              f'  |   File "{__file__}", line {exc.__code__.co_firstlineno + 1}, in exc\n'
              f'  |     raise ExceptionGroup("eg", [ValueError(1), TypeError(2)])\n'
-             f'  |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\n'
              f'  | ExceptionGroup: eg (2 sub-exceptions)\n'
              f'  +-+---------------- 1 ----------------\n'
              f'    | ValueError: 1\n'
@@ -1535,7 +1535,6 @@ def exc():
         expected = (f'  + Exception Group Traceback (most recent call last):\n'
                     f'  |   File "{__file__}", line {exc.__code__.co_firstlineno + 3}, in exc\n'
                     f'  |     raise EG("eg1", [ValueError(1), TypeError(2)])\n'
-                    f'  |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\n'
                     f'  | ExceptionGroup: eg1 (2 sub-exceptions)\n'
                     f'  +-+---------------- 1 ----------------\n'
                     f'    | ValueError: 1\n'
@@ -1548,10 +1547,8 @@ def exc():
                     f'  + Exception Group Traceback (most recent call last):\n'
                     f'  |   File "{__file__}", line {self.callable_line}, in get_exception\n'
                     f'  |     exception_or_callable()\n'
-                    f'  |     ^^^^^^^^^^^^^^^^^^^^^^^\n'
                     f'  |   File "{__file__}", line {exc.__code__.co_firstlineno + 5}, in exc\n'
                     f'  |     raise EG("eg2", [ValueError(3), TypeError(4)]) from e\n'
-                    f'  |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\n'
                     f'  | ExceptionGroup: eg2 (2 sub-exceptions)\n'
                     f'  +-+---------------- 1 ----------------\n'
                     f'    | ValueError: 3\n'
@@ -1577,7 +1574,6 @@ def exc():
              f'  + Exception Group Traceback (most recent call last):\n'
              f'  |   File "{__file__}", line {exc.__code__.co_firstlineno + 4}, in exc\n'
              f'  |     raise EG("eg1", [ValueError(1), TypeError(2)])\n'
-             f'  |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\n'
              f'  | ExceptionGroup: eg1 (2 sub-exceptions)\n'
              f'  +-+---------------- 1 ----------------\n'
              f'    | ValueError: 1\n'
@@ -1590,7 +1586,6 @@ def exc():
              f'  + Exception Group Traceback (most recent call last):\n'
              f'  |   File "{__file__}", line {exc.__code__.co_firstlineno + 6}, in exc\n'
              f'  |     raise EG("eg2", [ValueError(3), TypeError(4)])\n'
-             f'  |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\n'
              f'  | ExceptionGroup: eg2 (2 sub-exceptions)\n'
              f'  +-+---------------- 1 ----------------\n'
              f'    | ValueError: 3\n'
@@ -1603,10 +1598,8 @@ def exc():
              f'Traceback (most recent call last):\n'
              f'  File "{__file__}", line {self.callable_line}, in get_exception\n'
              f'    exception_or_callable()\n'
-             f'    ^^^^^^^^^^^^^^^^^^^^^^^\n'
              f'  File "{__file__}", line {exc.__code__.co_firstlineno + 8}, in exc\n'
              f'    raise ImportError(5)\n'
-             f'    ^^^^^^^^^^^^^^^^^^^^\n'
              f'ImportError: 5\n')
 
         report = self.get_report(exc)
@@ -1629,7 +1622,6 @@ def exc():
         expected = (f'  + Exception Group Traceback (most recent call last):\n'
                     f'  |   File "{__file__}", line {exc.__code__.co_firstlineno + 9}, in exc\n'
                     f'  |     raise EG("eg", [VE(1), exc, VE(4)])\n'
-                    f'  |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\n'
                     f'  | ExceptionGroup: eg (3 sub-exceptions)\n'
                     f'  +-+---------------- 1 ----------------\n'
                     f'    | ValueError: 1\n'
@@ -1637,7 +1629,6 @@ def exc():
                     f'    | Exception Group Traceback (most recent call last):\n'
                     f'    |   File "{__file__}", line {exc.__code__.co_firstlineno + 6}, in exc\n'
                     f'    |     raise EG("nested", [TE(2), TE(3)])\n'
-                    f'    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\n'
                     f'    | ExceptionGroup: nested (2 sub-exceptions)\n'
                     f'    +-+---------------- 1 ----------------\n'
                     f'      | TypeError: 2\n'
@@ -1653,10 +1644,8 @@ def exc():
                     f'  + Exception Group Traceback (most recent call last):\n'
                     f'  |   File "{__file__}", line {self.callable_line}, in get_exception\n'
                     f'  |     exception_or_callable()\n'
-                    f'  |     ^^^^^^^^^^^^^^^^^^^^^^^\n'
                     f'  |   File "{__file__}", line {exc.__code__.co_firstlineno + 11}, in exc\n'
                     f'  |     raise EG("top", [VE(5)])\n'
-                    f'  |     ^^^^^^^^^^^^^^^^^^^^^^^^\n'
                     f'  | ExceptionGroup: top (1 sub-exception)\n'
                     f'  +-+---------------- 1 ----------------\n'
                     f'    | ValueError: 5\n'
@@ -1814,10 +1803,8 @@ def exc():
         expected = (f'  + Exception Group Traceback (most recent call last):\n'
                     f'  |   File "{__file__}", line {self.callable_line}, in get_exception\n'
                     f'  |     exception_or_callable()\n'
-                    f'  |     ^^^^^^^^^^^^^^^^^^^^^^^\n'
                     f'  |   File "{__file__}", line {exc.__code__.co_firstlineno + 9}, in exc\n'
                     f'  |     raise ExceptionGroup("nested", excs)\n'
-                    f'  |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\n'
                     f'  | ExceptionGroup: nested (2 sub-exceptions)\n'
                     f'  | >> Multi line note\n'
                     f'  | >> Because I am such\n'
@@ -1829,14 +1816,12 @@ def exc():
                     f'    | Traceback (most recent call last):\n'
                     f'    |   File "{__file__}", line {exc.__code__.co_firstlineno + 5}, in exc\n'
                     f'    |     raise ValueError(msg)\n'
-                    f'    |     ^^^^^^^^^^^^^^^^^^^^^\n'
                     f'    | ValueError: bad value\n'
                     f'    | the bad value\n'
                     f'    +---------------- 2 ----------------\n'
                     f'    | Traceback (most recent call last):\n'
                     f'    |   File "{__file__}", line {exc.__code__.co_firstlineno + 5}, in exc\n'
                     f'    |     raise ValueError(msg)\n'
-                    f'    |     ^^^^^^^^^^^^^^^^^^^^^\n'
                     f'    | ValueError: terrible value\n'
                     f'    | the terrible value\n'
                     f'    +------------------------------------\n')
@@ -1869,10 +1854,8 @@ def exc():
         expected = (f'  + Exception Group Traceback (most recent call last):\n'
                     f'  |   File "{__file__}", line {self.callable_line}, in get_exception\n'
                     f'  |     exception_or_callable()\n'
-                    f'  |     ^^^^^^^^^^^^^^^^^^^^^^^\n'
                     f'  |   File "{__file__}", line {exc.__code__.co_firstlineno + 10}, in exc\n'
                     f'  |     raise ExceptionGroup("nested", excs)\n'
-                    f'  |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\n'
                     f'  | ExceptionGroup: nested (2 sub-exceptions)\n'
                     f'  | >> Multi line note\n'
                     f'  | >> Because I am such\n'
@@ -1885,7 +1868,6 @@ def exc():
                     f'    | Traceback (most recent call last):\n'
                     f'    |   File "{__file__}", line {exc.__code__.co_firstlineno + 5}, in exc\n'
                     f'    |     raise ValueError(msg)\n'
-                    f'    |     ^^^^^^^^^^^^^^^^^^^^^\n'
                     f'    | ValueError: bad value\n'
                     f'    | the bad value\n'
                     f'    | Goodbye bad value\n'
@@ -1893,7 +1875,6 @@ def exc():
                     f'    | Traceback (most recent call last):\n'
                     f'    |   File "{__file__}", line {exc.__code__.co_firstlineno + 5}, in exc\n'
                     f'    |     raise ValueError(msg)\n'
-                    f'    |     ^^^^^^^^^^^^^^^^^^^^^\n'
                     f'    | ValueError: terrible value\n'
                     f'    | the terrible value\n'
                     f'    | Goodbye terrible value\n'
@@ -2669,19 +2650,16 @@ def test_exception_group_format(self):
                     f'  + Exception Group Traceback (most recent call last):',
                     f'  |   File "{__file__}", line {lno_g+23}, in _get_exception_group',
                     f'  |     raise ExceptionGroup("eg2", [exc3, exc4])',
-                    f'  |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^',
                     f'  | ExceptionGroup: eg2 (2 sub-exceptions)',
                     f'  +-+---------------- 1 ----------------',
                     f'    | Exception Group Traceback (most recent call last):',
                     f'    |   File "{__file__}", line {lno_g+16}, in _get_exception_group',
                     f'    |     raise ExceptionGroup("eg1", [exc1, exc2])',
-                    f'    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^',
                     f'    | ExceptionGroup: eg1 (2 sub-exceptions)',
                     f'    +-+---------------- 1 ----------------',
                     f'      | Traceback (most recent call last):',
                     f'      |   File "{__file__}", line {lno_g+9}, in _get_exception_group',
                     f'      |     f()',
-                    f'      |     ^^^',
                     f'      |   File "{__file__}", line {lno_f+1}, in f',
                     f'      |     1/0',
                     f'      |     ~^~',
@@ -2690,20 +2668,16 @@ def test_exception_group_format(self):
                     f'      | Traceback (most recent call last):',
                     f'      |   File "{__file__}", line {lno_g+13}, in _get_exception_group',
                     f'      |     g(42)',
-                    f'      |     ^^^^^',
                     f'      |   File "{__file__}", line {lno_g+1}, in g',
                     f'      |     raise ValueError(v)',
-                    f'      |     ^^^^^^^^^^^^^^^^^^^',
                     f'      | ValueError: 42',
                     f'      +------------------------------------',
                     f'    +---------------- 2 ----------------',
                     f'    | Traceback (most recent call last):',
                     f'    |   File "{__file__}", line {lno_g+20}, in _get_exception_group',
                     f'    |     g(24)',
-                    f'    |     ^^^^^',
                     f'    |   File "{__file__}", line {lno_g+1}, in g',
                     f'    |     raise ValueError(v)',
-                    f'    |     ^^^^^^^^^^^^^^^^^^^',
                     f'    | ValueError: 24',
                     f'    +------------------------------------',
                     f'']

Lib/traceback.py

@@ -465,7 +465,8 @@ def format_frame_summary(self, frame_summary):
         row.append('  File "{}", line {}, in {}\n'.format(
             frame_summary.filename, frame_summary.lineno, frame_summary.name))
         if frame_summary.line:
-            row.append('    {}\n'.format(frame_summary.line.strip()))
+            stripped_line = frame_summary.line.strip()
+            row.append('    {}\n'.format(stripped_line))
 
             orig_line_len = len(frame_summary._original_line)
             frame_line_len = len(frame_summary.line.lstrip())
@@ -486,19 +487,22 @@ def format_frame_summary(self, frame_summary):
                             frame_summary._original_line[colno - 1:end_colno - 1]
                         )
                 else:
-                    end_colno = stripped_characters + len(frame_summary.line.strip())
+                    end_colno = stripped_characters + len(stripped_line)
 
-                row.append('    ')
+                # show indicators if primary char doesn't span the frame line
-                row.append(' ' * (colno - stripped_characters))
+                if end_colno - colno < len(stripped_line) or (
+                        anchors and anchors.right_start_offset - anchors.left_end_offset > 0):
+                    row.append('    ')
+                    row.append(' ' * (colno - stripped_characters))
 
-                if anchors:
+                    if anchors:
-                    row.append(anchors.primary_char * (anchors.left_end_offset))
+                        row.append(anchors.primary_char * (anchors.left_end_offset))
-                    row.append(anchors.secondary_char * (anchors.right_start_offset - anchors.left_end_offset))
+                        row.append(anchors.secondary_char * (anchors.right_start_offset - anchors.left_end_offset))
-                    row.append(anchors.primary_char * (end_colno - colno - anchors.right_start_offset))
+                        row.append(anchors.primary_char * (end_colno - colno - anchors.right_start_offset))
-                else:
+                    else:
-                    row.append('^' * (end_colno - colno))
+                        row.append('^' * (end_colno - colno))
 
-                row.append('\n')
+                    row.append('\n')
 
         if frame_summary.locals:
             for name, value in sorted(frame_summary.locals.items()):

Misc/NEWS.d/next/Core and Builtins/2022-06-24-14-06-20.gh-issue-93883.8jVQQ4.rst

@@ -0,0 +1 @@
+Revise the display strategy of traceback enhanced error locations.  The indicators are only shown when the location doesn't span the whole line.

Python/traceback.c

@@ -592,7 +592,6 @@ _Py_DisplaySourceLine(PyObject *f, PyObject *filename, int lineno, int indent,
  *  Traceback (most recent call last):
  *    File "/home/isidentical/cpython/cpython/t.py", line 10, in <module>
  *      add_values(1, 2, 'x', 3, 4)
- *      ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  *    File "/home/isidentical/cpython/cpython/t.py", line 2, in add_values
  *      return a + b + c + d + e
  *             ~~~~~~^~~
@@ -736,7 +735,7 @@ print_error_location_carets(PyObject *f, int offset, Py_ssize_t start_offset, Py
     int special_chars = (left_end_offset != -1 || right_start_offset != -1);
     const char *str;
     while (++offset <= end_offset) {
-        if (offset <= start_offset || offset > end_offset) {
+        if (offset <= start_offset) {
             str = " ";
         } else if (special_chars && left_end_offset < offset && offset <= right_start_offset) {
             str = secondary;
@@ -792,6 +791,7 @@ tb_displayline(PyTracebackObject* tb, PyObject *f, PyObject *filename, int linen
 
     int code_offset = tb->tb_lasti;
     PyCodeObject* code = frame->f_frame->f_code;
+    const Py_ssize_t source_line_len = PyUnicode_GET_LENGTH(source_line);
 
     int start_line;
     int end_line;
@@ -813,7 +813,7 @@ tb_displayline(PyTracebackObject* tb, PyObject *f, PyObject *filename, int linen
     //
     //  ERROR LINE ERROR LINE ERROR LINE ERROR LINE ERROR LINE ERROR LINE ERROR LINE
     //        ~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^~~~~~~~~~~~~~~~~~~~
-    //        |              |-> left_end_offset     |                  |-> left_offset
+    //        |              |-> left_end_offset     |                  |-> end_offset
     //        |-> start_offset                       |-> right_start_offset
     //
     // In general we will only have (start_offset, end_offset) but we can gather more information
@@ -822,6 +822,9 @@ tb_displayline(PyTracebackObject* tb, PyObject *f, PyObject *filename, int linen
     // the different ranges (primary_error_char and secondary_error_char). If we cannot obtain the
     // AST information or we cannot identify special ranges within it, then left_end_offset and
     // right_end_offset will be set to -1.
+    //
+    // To keep the column indicators pertinent, they are not shown when the primary character
+    // spans the whole line.
 
     // Convert the utf-8 byte offset to the actual character offset so we print the right number of carets.
     assert(source_line);
@@ -859,7 +862,7 @@ tb_displayline(PyTracebackObject* tb, PyObject *f, PyObject *filename, int linen
             goto done;
         }
 
-        Py_ssize_t i = PyUnicode_GET_LENGTH(source_line);
+        Py_ssize_t i = source_line_len;
         while (--i >= 0) {
             if (!IS_WHITESPACE(source_line_str[i])) {
                 break;
@@ -869,6 +872,13 @@ tb_displayline(PyTracebackObject* tb, PyObject *f, PyObject *filename, int linen
         end_offset = i + 1;
     }
 
+    // Elide indicators if primary char spans the frame line
+    Py_ssize_t stripped_line_len = source_line_len - truncation - _TRACEBACK_SOURCE_LINE_INDENT;
+    bool has_secondary_ranges = (left_end_offset != -1 || right_start_offset != -1);
+    if (end_offset - start_offset == stripped_line_len && !has_secondary_ranges) {
+        goto done;
+    }
+
     if (_Py_WriteIndentedMargin(margin_indent, margin, f) < 0) {
         err = -1;
         goto done;