Snoop doesn't load source code from compiled functions

[vikt0rs]

I'm trying to debug functions, generated from the source in runtime, but for some reason, snoop is unable to show the source code of such function. At the same time it shows variables and nested functions source - see an example below. Please, suggest, if I'm doing something wrong? Thanks!

Script output

    22:03:23.24 >>> Call to main in File "func_code", line 1
    22:03:23.24    1 | SOURCE IS UNAVAILABLE
    22:03:23.24    2 | SOURCE IS UNAVAILABLE
    22:03:23.24 ...... a = 2
    22:03:23.24    3 | SOURCE IS UNAVAILABLE
    22:03:23.24 ...... b = 3
    22:03:23.24    5 | SOURCE IS UNAVAILABLE
        22:03:23.33 >>> Call to Random.randint in File "/usr/local/Cellar/python@3.8/3.8.2/Frameworks/Python.framework/Versions/3.8/lib/python3.8/random.py", line 244
        22:03:23.33 .......... self = <random.Random object at 0x7ff952003810>
        22:03:23.33 .......... a = 1
        22:03:23.33 .......... b = 100
        22:03:23.33  244 |     def randint(self, a, b):
        22:03:23.34  248 |         return self.randrange(a, b+1)
        22:03:23.34 <<< Return value from Random.randint: 20
    22:03:23.34    5 | SOURCE IS UNAVAILABLE
    22:03:23.34 ...... c = 25
    22:03:23.34    7 | SOURCE IS UNAVAILABLE
    22:03:23.34 <<< Return value from main: 25

Script code

import types
import random

import snoop


func_text = """def main():
        a = 2
        b = 3
        c = a + b + random.randint(1, 100)
        return c"""

func_code = compile(
    source=func_text,
    filename="func_code",
    mode='exec',
)

tracer = snoop.snoop(depth=3)

func = types.FunctionType(
    func_code.co_consts[0],
    {
        "random": random,
        "tracer": tracer,
    },
    'func'
)


if __name__ == '__main__':
    with tracer:
        func()

[alexmojaki]

The source code is truly unavailable. It's not stored in the code object and Python doesn't know where to find it because func_code is not a real filename. If you raise an exception inside the compiled code, the traceback won't show the source code either.

You can create a real file, write func_text into it, and pass the actual filename to compile. If that's not an option, you can put the lines directly into the cache of the linecache module.

[vikt0rs]

This sounds like a hack, but works! Thanks a lot for your help!

[alexmojaki]

You can also accomplish your main goal more elegantly with exec:

import random
import math
source = """
def main():
    print(random)
    print(math)
"""
code = compile(
    source=source,
    filename="<filename>",
    mode='exec',
)
globs = {"random": random}
exec(code, globs)
globs["main"]()

This prints the random module but fails on math because that wasn't included in the custom globals dictionary.