bpo-45249: Ensure the traceback module prints correctly syntax errors with ranges (GH-28575)

Author: pablogsal

Lib/test/test_traceback.py

@@ -43,6 +43,9 @@ def syntax_error_with_caret(self):
     def syntax_error_with_caret_2(self):
         compile("1 +\n", "?", "exec")
 
+    def syntax_error_with_caret_range(self):
+        compile("f(x, y for y in range(30), z)", "?", "exec")
+
     def syntax_error_bad_indentation(self):
         compile("def spam():\n  print(1)\n print(2)", "?", "exec")
 
@@ -59,18 +62,28 @@ def test_caret(self):
         self.assertTrue(err[1].strip() == "return x!")
         self.assertIn("^", err[2]) # third line has caret
         self.assertEqual(err[1].find("!"), err[2].find("^")) # in the right place
+        self.assertEqual(err[2].count("^"), 1)
 
         err = self.get_exception_format(self.syntax_error_with_caret_2,
                                         SyntaxError)
         self.assertIn("^", err[2]) # third line has caret
         self.assertEqual(err[2].count('\n'), 1)   # and no additional newline
         self.assertEqual(err[1].find("+") + 1, err[2].find("^"))  # in the right place
+        self.assertEqual(err[2].count("^"), 1)
 
         err = self.get_exception_format(self.syntax_error_with_caret_non_ascii,
                                         SyntaxError)
         self.assertIn("^", err[2]) # third line has caret
         self.assertEqual(err[2].count('\n'), 1)   # and no additional newline
         self.assertEqual(err[1].find("+") + 1, err[2].find("^"))  # in the right place
+        self.assertEqual(err[2].count("^"), 1)
+
+        err = self.get_exception_format(self.syntax_error_with_caret_range,
+                                        SyntaxError)
+        self.assertIn("^", err[2]) # third line has caret
+        self.assertEqual(err[2].count('\n'), 1)   # and no additional newline
+        self.assertEqual(err[1].find("y"), err[2].find("^"))  # in the right place
+        self.assertEqual(err[2].count("^"), len("y for y in range(30)"))
 
     def test_nocaret(self):
         exc = SyntaxError("error", ("x.py", 23, None, "bad syntax"))

Lib/traceback.py

@@ -622,10 +622,14 @@ class TracebackException:
       occurred.
     - :attr:`lineno` For syntax errors - the linenumber where the error
       occurred.
+    - :attr:`end_lineno` For syntax errors - the end linenumber where the error
+      occurred. Can be `None` if not present.
     - :attr:`text` For syntax errors - the text where the error
       occurred.
     - :attr:`offset` For syntax errors - the offset into the text where the
       error occurred.
+    - :attr:`end_offset` For syntax errors - the offset into the text where the
+      error occurred. Can be `None` if not present.
     - :attr:`msg` For syntax errors - the compiler error message.
     """
 
@@ -655,8 +659,11 @@ def __init__(self, exc_type, exc_value, exc_traceback, *, limit=None,
             self.filename = exc_value.filename
             lno = exc_value.lineno
             self.lineno = str(lno) if lno is not None else None
+            end_lno = exc_value.end_lineno
+            self.end_lineno = str(end_lno) if end_lno is not None else None
             self.text = exc_value.text
             self.offset = exc_value.offset
+            self.end_offset = exc_value.end_offset
             self.msg = exc_value.msg
         if lookup_lines:
             self._load_lines()
@@ -771,12 +778,20 @@ def _format_syntax_error(self, stype):
             ltext = rtext.lstrip(' \n\f')
             spaces = len(rtext) - len(ltext)
             yield '    {}\n'.format(ltext)
-            # Convert 1-based column offset to 0-based index into stripped text
-            caret = (self.offset or 0) - 1 - spaces
-            if caret >= 0:
-                # non-space whitespace (likes tabs) must be kept for alignment
-                caretspace = ((c if c.isspace() else ' ') for c in ltext[:caret])
-                yield '    {}^\n'.format(''.join(caretspace))
+
+            if self.offset is not None:
+                offset = self.offset
+                end_offset = self.end_offset if self.end_offset is not None else offset
+                if offset == end_offset or end_offset == -1:
+                    end_offset = offset + 1
+
+                # Convert 1-based column offset to 0-based index into stripped text
+                colno = offset - 1 - spaces
+                end_colno = end_offset - 1 - spaces
+                if colno >= 0:
+                    # non-space whitespace (likes tabs) must be kept for alignment
+                    caretspace = ((c if c.isspace() else ' ') for c in ltext[:colno])
+                    yield '    {}{}'.format("".join(caretspace), ('^' * (end_colno - colno) + "\n"))
         msg = self.msg or "<no detail available>"
         yield "{}: {}{}\n".format(stype, msg, filename_suffix)