bpo-43950: support some multi-line expressions for PEP 657 (GH-27339)

This is basically something that I noticed up while fixing test runs for another issue. It is really common to have multiline calls, and when they fail the display is kind of weird since we omit the annotations. E.g;

```
 $ ./python t.py
Traceback (most recent call last):
  File "/home/isidentical/cpython/cpython/t.py", line 11, in <module>
    frame_1()
    ^^^^^^^^^
  File "/home/isidentical/cpython/cpython/t.py", line 5, in frame_1
    frame_2(
  File "/home/isidentical/cpython/cpython/t.py", line 2, in frame_2
    return a / 0 / b / c
           ~~^~~
ZeroDivisionError: division by zero
```

This patch basically adds support for annotating the rest of the line, if the instruction covers multiple lines (start_line != end_line).

Automerge-Triggered-By: GH:isidentical

diff --git a/Lib/test/test_doctest.py b/Lib/test/test_doctest.py
index 642188fd5ea48e4f72dede4abc3194938c04b7d3..8f761d7a52c23e8bab0ba00c5d129ba2b02f9505 100644 (file)
--- a/Lib/test/test_doctest.py
+++ b/Lib/test/test_doctest.py
@@ -2835,6 +2835,7 @@ Check doctest with a non-ascii filename:
         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')
             ^^^^^^^^^^^^^^^^^^^^^^

diff --git a/Lib/test/test_traceback.py b/Lib/test/test_traceback.py
index 5fc5b5926d5a67d063c4f6fba6f8b0008ca52eeb..5d48e9d7ff0397da8150c08950d2e5d5b12cb74a 100644 (file)
--- a/Lib/test/test_traceback.py
+++ b/Lib/test/test_traceback.py
@@ -429,6 +429,30 @@ class TracebackErrorLocationCaretTests(unittest.TestCase):
             '    ^^^^^^^^^^\n'
             f'  File "{__file__}", line {lineno_f+1}, in f_with_multiline\n'
             '    raise ValueError(\n'
+            '    ^^^^^^^^^^^^^^^^^'
+        )
+        result_lines = self.get_exception(f_with_multiline)
+        self.assertEqual(result_lines, expected_f.splitlines())
+
+    def test_caret_multiline_expression_bin_op(self):
+        # Make sure no carets are printed for expressions spanning multiple
+        # lines.
+        def f_with_multiline():
+            return (
+                1 /
+                0 +
+                2
+            )
+
+        lineno_f = f_with_multiline.__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+2}, in f_with_multiline\n'
+            '    1 /\n'
+            '    ^^^'
         )
         result_lines = self.get_exception(f_with_multiline)
         self.assertEqual(result_lines, expected_f.splitlines())

diff --git a/Lib/traceback.py b/Lib/traceback.py
index 15bdb3c8c2e650af157c3d77877ba903279a6619..4ad8c9a17b349c1c1573c7e8ad521aa148875501 100644 (file)
--- a/Lib/traceback.py
+++ b/Lib/traceback.py
@@ -4,6 +4,7 @@ import collections
 import itertools
 import linecache
 import sys
+from contextlib import suppress
 
 __all__ = ['extract_stack', 'extract_tb', 'format_exception',
            'format_exception_only', 'format_list', 'format_stack',
@@ -463,19 +464,20 @@ class StackSummary(list):
 
             stripped_characters = len(frame._original_line) - len(frame.line.lstrip())
             if (
-                frame.end_lineno == frame.lineno
-                and frame.colno is not None
+                frame.colno is not None
                 and frame.end_colno is not None
             ):
                 colno = _byte_offset_to_character_offset(frame._original_line, frame.colno)
                 end_colno = _byte_offset_to_character_offset(frame._original_line, frame.end_colno)
 
-                try:
-                    anchors = _extract_caret_anchors_from_line_segment(
-                        frame._original_line[colno - 1:end_colno - 1]
-                    )
-                except Exception:
-                    anchors = None
+                anchors = None
+                if frame.lineno == frame.end_lineno:
+                    with suppress(Exception):
+                        anchors = _extract_caret_anchors_from_line_segment(
+                            frame._original_line[colno - 1:end_colno - 1]
+                        )
+                else:
+                    end_colno = stripped_characters + len(frame.line.strip())
 
                 row.append('    ')
                 row.append(' ' * (colno - stripped_characters))

diff --git a/Python/traceback.c b/Python/traceback.c
index 61e6838e17e4191a8eee5e25853e400b3d8e4f6e..6d230138a3c7772c693d6459322dcf95633f25db 100644 (file)
--- a/Python/traceback.c
+++ b/Python/traceback.c
@@ -720,11 +720,11 @@ tb_displayline(PyTracebackObject* tb, PyObject *f, PyObject *filename, int linen
                               &end_line, &end_col_byte_offset)) {
         goto done;
     }
-    if (start_line != end_line) {
-        goto done;
-    }
 
-    if (start_col_byte_offset < 0 || end_col_byte_offset < 0) {
+    if (start_line < 0 || end_line < 0
+        || start_col_byte_offset < 0
+        || end_col_byte_offset < 0)
+    {
         goto done;
     }
 
@@ -762,11 +762,30 @@ tb_displayline(PyTracebackObject* tb, PyObject *f, PyObject *filename, int linen
     char *primary_error_char = "^";
     char *secondary_error_char = primary_error_char;
 
-    int res = extract_anchors_from_line(filename, source_line, start_offset, end_offset,
-                                        &left_end_offset, &right_start_offset,
-                                        &primary_error_char, &secondary_error_char);
-    if (res < 0 && ignore_source_errors() < 0) {
-        goto done;
+    if (start_line == end_line) {
+        int res = extract_anchors_from_line(filename, source_line, start_offset, end_offset,
+                                            &left_end_offset, &right_start_offset,
+                                            &primary_error_char, &secondary_error_char);
+        if (res < 0 && ignore_source_errors() < 0) {
+            goto done;
+        }
+    }
+    else {
+        // If this is a multi-line expression, then we will highlight until
+        // the last non-whitespace character.
+        const char *source_line_str = PyUnicode_AsUTF8(source_line);
+        if (!source_line_str) {
+            goto done;
+        }
+
+        Py_ssize_t i = PyUnicode_GET_LENGTH(source_line);
+        while (--i >= 0) {
+            if (!IS_WHITESPACE(source_line_str[i])) {
+                break;
+            }
+        }
+
+        end_offset = i + 1;
     }
 
     err = print_error_location_carets(f, truncation, start_offset, end_offset,