When a decorater contains a `lambda` declaration, using the pdb command `longlist` will show only the definition of the decorator.  The definition of the function itself is not shown:


cat mini.py

#!/usr/bin/python3.4

def foo(x, y=None):
    return x

@foo(foo, lambda a:a)
def spam():
    0+0
    1+1
    1/0

spam()
$ python3.4 -mpdb mini.py                                                                                                                                               
> /tmp/mini.py(3)<module>()
-> def foo(x, y=None):
(Pdb) cont
Traceback (most recent call last):
  File "/usr/lib64/python3.4/pdb.py", line 1661, in main
    pdb._runscript(mainpyfile)
  File "/usr/lib64/python3.4/pdb.py", line 1542, in _runscript
    self.run(statement)
  File "/usr/lib64/python3.4/bdb.py", line 431, in run
    exec(cmd, globals, locals)
  File "<string>", line 1, in <module>
  File "/tmp/mini.py", line 3, in <module>
    def foo(x, y=None):
  File "/tmp/mini.py", line 10, in spam
    1/0
ZeroDivisionError: division by zero
Uncaught exception. Entering post mortem debugging
Running 'cont' or 'step' will restart the program
> /tmp/mini.py(10)spam()
-> 1/0
(Pdb) longlist
  6     @foo(foo, lambda a:a)
(Pdb) 


The last line illustrates the problem.  `longlist` should show the definition of `spam`, not just the decorator.

I think this has been fixed by now, because I don't see the problem in Python 3.10:

python.bat -mpdb tmp1.py
Running Release|Win32 interpreter...
> c:\users\user\src\cpython\tmp1.py(2)<module>()
-> def foo(x, y=None):
(Pdb) c
Traceback (most recent call last):
  File "C:\Users\User\src\cpython\lib\pdb.py", line 1740, in main
    pdb._runscript(mainpyfile)
  File "C:\Users\User\src\cpython\lib\pdb.py", line 1609, in _runscript
    self.run(statement)
  File "C:\Users\User\src\cpython\lib\bdb.py", line 580, in run
    exec(cmd, globals, locals)
  File "<string>", line 1, in <module>
  File "c:\users\user\src\cpython\tmp1.py", line 2, in <module>
    def foo(x, y=None):
  File "c:\users\user\src\cpython\tmp1.py", line 9, in spam
    1/0
ZeroDivisionError: division by zero
Uncaught exception. Entering post mortem debugging
Running 'cont' or 'step' will restart the program
> c:\users\user\src\cpython\tmp1.py(9)spam()
-> 1/0
(Pdb) longlist
  5     @foo(foo, lambda a:a)
  6     def spam():
  7         0+0
  8         1+1
  9  ->     1/0
(Pdb)

pdb uses inspect.findsource for this, where this problem was fixed in issue 1764286.

I believe this ticket can be closed.