JoblibCollisionWarning not shown in an interactive session

[lesteve]

Seen in #648, the doc describing the behaviour with JoblibCollisionWarning does not correspond to the observed behaviour in an IPython console or Jupyter notebook. It seems to be more or less fine if the code is in a python file.

I'll try to add more details soon.

[lesteve]

# test-collision.py
from joblib import Memory

memory = Memory('/tmp/test')
memory.clear(warn=False)


def func(x):
    print('Running one(%s)' % x)
    return 1


one = memory.cache(func)


def func(x):
    print('Running two(%s)' % x)
    return 2


two = memory.cache(func)

print('first call')
print('-'*80)
print('result one:', one(1))
print('result two:', two(1))
print('second call')
print('-'*80)
print('result one:', one(1))
print('result two:', two(1))

$ ipython test-collision.py

first call
--------------------------------------------------------------------------------
________________________________________________________________________________
[Memory] Calling __main__--tmp-test-joblib.func...
func(1)
Running one(1)
_____________________________________________________________func - 0.0s, 0.0min
result one: 1
/tmp/test-joblib.py:25: JobLibCollisionWarning: Possible name collisions between functions 'func' (/tmp/test-joblib.py:7) and 'func' (/tmp/test-joblib.py:15)
  print('result two:', two(1))
WARNING:root:[MemorizedFunc(func=<function func at 0x7f8412fd6a60>, location=/tmp/test/joblib)]: Clearing function cache identified by __main__--tmp-test-joblib/func
________________________________________________________________________________
[Memory] Calling __main__--tmp-test-joblib.func...
func(1)
Running two(1)
_____________________________________________________________func - 0.0s, 0.0min
result two: 2
second call
--------------------------------------------------------------------------------
result one: 2
result two: 2

Copying and pasting the same snippet in a IPython session:

first call
--------------------------------------------------------------------------------
________________________________________________________________________________
[Memory] Calling __main__--home-lesteve-dev-joblib-__ipython-input__.func...
func(1)
Running one(1)
_____________________________________________________________func - 0.0s, 0.0min
result one: 1
WARNING:root:[MemorizedFunc(func=<function func at 0x7f5eb12a1048>, location=/tmp/test/joblib)]: Clearing function cache identified by __main__--home-lesteve-dev-joblib-__ipython-input__/func
________________________________________________________________________________
[Memory] Calling __main__--home-lesteve-dev-joblib-__ipython-input__.func...
func(1)
Running two(1)
_____________________________________________________________func - 0.0s, 0.0min
result two: 2
second call
--------------------------------------------------------------------------------
result one: 2
result two: 2

To sum up the difference is a JoblibCollisionWarning or a normal warning. Granted the former has a little bit more details explaining the problem but in the grand scheme of things this may not make a big difference.

To be honest I am not sure what the behaviour should be (cc @GaelVaroquaux who may have an opinion on this edge case). It is nice to have a warning but it looks like the calling one the second time will load the cached result from two which seems not so great.