bpo-34463: Make python tracebacks identical to C tracebacks for SyntaxErrors without a lineno (GH-23427)

(cherry picked from commit 069560b1171eb6385121ff3b6331e8814a4e7454)

Co-authored-by: Irit Katriel <iritkatriel@yahoo.com>

1 files changed, 9 insertions, 5 deletions

diff --git a/Lib/traceback.py b/Lib/traceback.py
index fb34de9489..d7fbdae680 100644
--- a/Lib/traceback.py
+++ b/Lib/traceback.py
@@ -515,7 +515,8 @@ class TracebackException:
         if exc_type and issubclass(exc_type, SyntaxError):
             # Handle SyntaxError's specially
             self.filename = exc_value.filename
-            self.lineno = str(exc_value.lineno)
+            lno = exc_value.lineno
+            self.lineno = str(lno) if lno is not None else None
             self.text = exc_value.text
             self.offset = exc_value.offset
             self.msg = exc_value.msg
@@ -574,9 +575,12 @@ class TracebackException:
     def _format_syntax_error(self, stype):
         """Format SyntaxError exceptions (internal helper)."""
         # Show exactly where the problem was found.
-        filename = self.filename or "<string>"
-        lineno = str(self.lineno) or '?'
-        yield '  File "{}", line {}\n'.format(filename, lineno)
+        filename_suffix = ''
+        if self.lineno is not None:
+            yield '  File "{}", line {}\n'.format(
+                self.filename or "<string>", self.lineno)
+        elif self.filename is not None:
+            filename_suffix = ' ({})'.format(self.filename)
 
         text = self.text
         if text is not None:
@@ -594,7 +598,7 @@ class TracebackException:
                 caretspace = ((c if c.isspace() else ' ') for c in ltext[:caret])
                 yield '    {}^\n'.format(''.join(caretspace))
         msg = self.msg or "<no detail available>"
-        yield "{}: {}\n".format(stype, msg)
+        yield "{}: {}{}\n".format(stype, msg, filename_suffix)
 
     def format(self, *, chain=True):
         """Format the exception.