Feature request: support recursion, including with depth argument

[zengxiaofei]

For example:

from __future__ import print_function
import pysnooper

@pysnooper.snoop()
def fact(n):
    if n == 1:
        return 1
    return n * fact(n - 1)

def main():
    print(fact(3))

if __name__ == '__main__':
    main()

Output:

$ python mytest2.py 
Starting var:.. n = 3
01:22:43.094346 call         4 @pysnooper.snoop()
01:22:43.095271 line         6     if n == 1:
01:22:43.095435 line         8     return n * fact(n - 1)
Starting var:.. n = 2
01:22:43.095591 call         4 @pysnooper.snoop()
01:22:43.095664 line         6     if n == 1:
01:22:43.095722 line         8     return n * fact(n - 1)
Starting var:.. n = 1
01:22:43.095830 call         4 @pysnooper.snoop()
01:22:43.095884 line         6     if n == 1:
01:22:43.095941 line         7         return 1
01:22:43.096022 return       7         return 1
01:22:43.096110 return       8     return n * fact(n - 1)
01:22:43.096175 return       8     return n * fact(n - 1)
6

When setting depth=2, it even raised an error:

Starting var:.. n = 3
01:26:47.652684 call         4 @pysnooper.snoop(depth=2)
01:26:47.653612 line         6     if n == 1:
01:26:47.653684 line         8     return n * fact(n - 1)
    Starting var:.. n = 2
Traceback (most recent call last):
  File "mytest2.py", line 14, in <module>
    main()
  File "mytest2.py", line 11, in main
    print(fact(3))
  File "</home/xiaofei/.local/lib/python2.7/site-packages/decorator.pyc:decorator-gen-2>", line 2, in fact
  File "/home/xiaofei/.local/lib/python2.7/site-packages/pysnooper/pysnooper.py", line 72, in decorate
    return function(*args, **kwargs)
  File "mytest2.py", line 8, in fact
    return n * fact(n - 1)
  File "</home/xiaofei/.local/lib/python2.7/site-packages/decorator.pyc:decorator-gen-2>", line 1, in fact
  File "/home/xiaofei/.local/lib/python2.7/site-packages/pysnooper/tracer.py", line 182, in trace
    source_line = get_source_from_frame(frame)[frame.f_lineno - 1]
  File "/home/xiaofei/.local/lib/python2.7/site-packages/pysnooper/tracer.py", line 75, in get_source_from_frame
    raise NotImplementedError
NotImplementedError

[cool-RR]

Good feature request. Feel free to submit a pull request.

[alexmojaki]

This works now. I'm guessing the error was essentially the same issue encountered in #109 and fixed in #112. Making the output look a little nicer is being worked on in #108, although I don't think it needs to be merged to count this as fixed.