[New-bugs-announce] [issue44672] Final "pass" is traced incorrectly in 3.9 (and before)

[Ned Batchelder]

New submission from Ned Batchelder <ned at nedbatchelder.com>:

A simple function with a last "pass" statement gets traced incorrectly, attributing the return to the pass instead of the actual last statement executed:

--- 8< --------------------------
import linecache, sys

def trace(frame, event, arg):
    # The weird globals here is to avoid a NameError on shutdown...
    if frame.f_code.co_filename == globals().get("__file__"):
        lineno = frame.f_lineno
        print("{} {}: {}".format(event[:4], lineno, linecache.getline(__file__, lineno).rstrip()))
    return trace

def wrong_loop(x):
    if x:
        if x:
            print(4)
    else:
        pass

print(sys.version)
sys.settrace(trace)

wrong_loop(8)
----------------------------------

On 3.9 and before, this produces:

3.9.5 (default, May  5 2021, 06:50:43)
[Clang 12.0.0 (clang-1200.0.32.29)]
call 10: def wrong_loop(x):
line 11:     if x:
line 12:         if x:
line 13:             print(4)
4
line 15:         pass
retu 15:         pass

Partly I'm writing this issue to record the problem, but partly to get a decision: will there be fixes made to 3.9 (or before) for issues like this?

----------
components: Interpreter Core
messages: 397791
nosy: Mark.Shannon, nedbat
priority: normal
severity: normal
status: open
title: Final "pass" is traced incorrectly in 3.9 (and before)
type: behavior
versions: Python 3.6, Python 3.7, Python 3.8, Python 3.9

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue44672>
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