Clock.callLater(0, f) can lead to infinite loop

[exarkun]

Consider:

from twisted.internet.task import Clock

def f():
    c.callLater(0, f)

c = Clock()
f()
c.advance(0)
print 'Done'

The expected behavior is that f runs once and then Done is printed and the program exits. Instead, Clock.advance spends forever running and re-running f. This is similar to a bug that the real IReactorTime implementation used to have but that we fixed.

[itamar]

This ticket is easy if it only fixes the Clock issue. In which the "it would be nice" part of merging it with the reactor implementation should get its own ticket.

[exarkun]

In which the "it would be nice" part of merging it with the reactor implementation should get its own ticket.

Want to file that? :)

[itamar]

OK, I moved the "it would be nice" feature to a separate ticket, #6425.

[itamar]

Thanks for the patch! The basic logic makes sense to me, and the test does indeed fail without the code and pass with it.

There remain a few minor issues:

1. The code is confusing if you don't know the reason tempCalls exists; perhaps some explanatory comments, and better variable names ("_insideAdvance" maybe instead of "checkLoop"?) would make it clearer why that code exists.
2. The code should have a news file ( https://twistedmatrix.com/trac/wiki/ReviewProcess#Newsfiles). If you "svn add" it then it will be included when you run "svn diff".
3. The tests variables really don't need to be set on self, just use local variables.
4. The code should follow the coding standard; in particular the test code does not. Keep in mind that some code is old and doesn't quite follow the standard yet. E.g. test methods should start with "test_", but other tests in that module don't yet.
5. The docstring for the test should explain in more detail what behavior you expect. Also, it shouldn't start with "check that" or "test that". Rather, something like "If a function called by Clock.advance(0) reschedules itself with a delay of 0, then it should" etc..

Please resubmit with fixes for these issues.

[Saurabh]

Thanks for the reply and suggestions! I will work on those issues now.

[Saurabh]

Added topfile, better variable names,comments.