Report a missing line number instead of reconstructing one

Per review, do not try to recover a line number for a frame stopped on
an instruction that carries no line: just skip the source-context
lookup that assumed lineno was an int, and let getframeinfo() report
lineno, code_context and index as None.

The previous approach did not work anyway.  _lasti2lineno() walked
dis.findlinestarts(), which since 3.11 yields None line numbers of its
own, so it returned None for exactly the frames it was meant to fix.

Add a regression test that reproduces the original TypeError.

Author: graingert

Lib/inspect.py

@@ -1609,10 +1609,10 @@ def getframeinfo(frame, context=1):
     to return, which are centered around the current line."""
     if istraceback(frame):
         positions = _get_code_position_from_tb(frame)
-        lineno = _tblineno(frame)
+        lineno = frame.tb_lineno
         frame = frame.tb_frame
     else:
-        lineno = getlineno(frame)
+        lineno = frame.f_lineno
         positions = _get_code_position(frame.f_code, frame.f_lasti)
 
     if positions[0] is None:
@@ -1626,7 +1626,7 @@ def getframeinfo(frame, context=1):
         raise TypeError('{!r} is not a frame or traceback object'.format(frame))
 
     filename = getsourcefile(frame) or getfile(frame)
-    if context > 0:
+    if context > 0 and lineno is not None:
         start = lineno - 1 - context//2
         try:
             lines, lnum = findsource(frame)
@@ -1642,34 +1642,9 @@ def getframeinfo(frame, context=1):
     return Traceback(filename, lineno, frame.f_code.co_name, lines,
                      index, positions=dis.Positions(*positions))
 
-
-def _tblineno(tb):
-    tb_lineno = tb.tb_lineno
-    if tb_lineno is not None:
-        return tb_lineno
-
-    return _lasti2lineno(tb.tb_frame.f_code, tb.tb_lasti)
-
-
-def _lasti2lineno(code, lasti):
-    prev_line = code.co_firstlineno
-
-    for start, next_line in dis.findlinestarts(code):
-        if lasti < start:
-            return prev_line
-        prev_line = next_line
-
-    return prev_line
-
 def getlineno(frame):
     """Get the line number from a frame object, allowing for optimization."""
-    # FrameType.f_lineno is now a descriptor that often grovels co_lnotab
-    f_lineno = frame.f_lineno
-    if f_lineno is not None:
-        return f_lineno
-
-    return _lasti2lineno(frame.f_code, frame.f_lasti)
-
+    return frame.f_lineno
 
 _FrameInfo = namedtuple('_FrameInfo', ('frame',) + Traceback._fields)
 class FrameInfo(_FrameInfo):

Lib/test/test_inspect/test_inspect.py

@@ -846,6 +846,39 @@ def test_getframeinfo_get_first_line(self):
         self.assertEqual(frame_info.code_context[0], "# line 1\n")
         self.assertEqual(frame_info.code_context[1], "'A module docstring.'\n")
 
+    def test_getframeinfo_no_lineno(self):
+        # gh-89726: some instructions carry no line number, so a frame
+        # stopped on one has f_lineno set to None.  getframeinfo() must
+        # report that rather than failing.
+        def f():
+            try:
+                raise ValueError
+            except ValueError:
+                pass
+
+        infos = []
+
+        def trace(frame, event, arg):
+            if frame.f_code is f.__code__ and frame.f_lineno is None:
+                infos.append(inspect.getframeinfo(frame))
+            frame.f_trace_opcodes = True
+            return trace
+
+        old_trace = sys.gettrace()
+        sys.settrace(trace)
+        try:
+            f()
+        finally:
+            sys.settrace(old_trace)
+
+        self.assertTrue(infos, 'no frame with f_lineno set to None')
+        for info in infos:
+            with self.subTest(info=info):
+                self.assertIsNone(info.lineno)
+                self.assertIsNone(info.code_context)
+                self.assertIsNone(info.index)
+                self.assertEqual(info.function, 'f')
+
     def test_getsource(self):
         self.assertSourceEqual(git.abuse, 29, 39)
         self.assertSourceEqual(mod.StupidGit, 21, 51)

Misc/NEWS.d/next/Library/2022-03-22-10-16-11.bpo-45563.o-oP2m.rst

@@ -1 +1,4 @@
-handle frame.f_lineno is None in inspect.getframeinfo
+:func:`inspect.getframeinfo` no longer raises :exc:`TypeError` for a frame
+stopped on an instruction that carries no line number, such as while tracing
+opcodes.  ``lineno``, ``code_context`` and ``index`` are reported as ``None``
+instead.