Coverage with/after pdb.set_trace

[blueyed]

Given t-coverage.py:

import sys


print(1)

trace = sys.gettrace()

__import__('pdb').set_trace()

sys.settrace(trace)

print(2)
print(3)

Running coverage run t-coverage.py && coverage report -m t-coverage.py results in:

1
> /home/daniel/Vcs/coveragepy/t-coverage.py(10)<module>()
-> sys.settrace(trace)
(Pdb) c
2
3
Name            Stmts   Miss  Cover   Missing
---------------------------------------------
t-coverage.py       7      3    57%   10-13

coverage annotate shows that the pdb.set_trace() and the code after it is not covered:

! sys.settrace(trace)
  
! print(2)
! print(3)

I have seen #647, but the issue there appears to be different.
It was mentioned there that it might work if chained correctly, which I've tried to achieve by (re)storing the previous trace function: #647 (comment)

Is this what was meant, or would the wrapping/chaining need to happen in another way?

Python 3.7.1
Coverage.py, version 4.5.1 with C extension

[blueyed]

I think it would be good for pdb itself to set a function on sys.settrace, which would call the original function (i.e. coverage.py's) after its own processing, and not set it to None in the end, but restore the previous one.