[3.10] bpo-44446: support lineno being None in traceback.FrameSummary (GH-26781) (GH-27072)

As of 088a15c, lineno is None instead
of -1 if there is no line number.

Signed-off-by: Filipe Laíns <lains@riseup.net>.
(cherry picked from commit 91a8f8c)

Co-authored-by: Filipe Laíns <lains@riseup.net>

Co-authored-by: Filipe Laíns <lains@riseup.net>

Author: pablogsal

Lib/test/test_traceback.py

@@ -1001,6 +1001,10 @@ def test_lazy_lines(self):
             '"""Test cases for traceback module"""',
             f.line)
 
+    def test_no_line(self):
+        f = traceback.FrameSummary("f", None, "dummy")
+        self.assertEqual(f.line, None)
+
     def test_explicit_line(self):
         f = traceback.FrameSummary("f", 1, "dummy", line="line")
         self.assertEqual("line", f.line)

Lib/traceback.py

@@ -301,9 +301,10 @@ def __len__(self):
     @property
     def line(self):
         if self._line is None:
-            self._line = linecache.getline(self.filename, self.lineno).strip()
-        return self._line
-
+            if self.lineno is None:
+                return None
+            self._line = linecache.getline(self.filename, self.lineno)
+        return self._line.strip()
 
 def walk_stack(f):
     """Walk a stack yielding the frame and line number for each frame.

Misc/NEWS.d/next/Library/2021-06-17-22-39-34.bpo-44446.qwdRic.rst

@@ -0,0 +1 @@
+Take into account that ``lineno`` might be ``None`` in :class:`traceback.FrameSummary`.