Fix unhandling of possible recursion error on ExceptionRecord.__deepcopy__

[uael]

While using mobly and aio gRPC, the following very long trace pop on gRPC aio error. Although this might not be Mobly related, since deepcopy can trigger a RecursionError I think it make sense to handle it. This change fix that.

Trace (cut for readability):

AioRpcError
[ExampleTest] 02-06 15:47:34.895 ERROR Exception happened when executing on_fail for test.
Traceback (most recent call last):
  File "venv/lib/python3.10/site-packages/mobly/base_test.py", line 640, in _exec_procedure_func
    func(copy.deepcopy(tr_record))
  File "/usr/lib/python3.10/copy.py", line 172, in deepcopy
    y = _reconstruct(x, memo, *rv)
  File "/usr/lib/python3.10/copy.py", line 271, in _reconstruct
    state = deepcopy(state, memo)
  File "/usr/lib/python3.10/copy.py", line 146, in deepcopy
    y = copier(x, memo)
  File "/usr/lib/python3.10/copy.py", line 231, in _deepcopy_dict
    y[deepcopy(key, memo)] = deepcopy(value, memo)
  File "/usr/lib/python3.10/copy.py", line 153, in deepcopy
    y = copier(memo)
  File "venv/lib/python3.10/site-packages/mobly/records.py", line 280, in __deepcopy__
    exception = copy.deepcopy(self.exception)
  File "/usr/lib/python3.10/copy.py", line 172, in deepcopy
    y = _reconstruct(x, memo, *rv)
  File "/usr/lib/python3.10/copy.py", line 265, in _reconstruct
    y = func(*args)
  File "/usr/lib/python3.10/copy.py", line 264, in <genexpr>
    args = (deepcopy(arg, memo) for arg in args)
  File "/usr/lib/python3.10/copy.py", line 172, in deepcopy
    y = _reconstruct(x, memo, *rv)
  File "/usr/lib/python3.10/copy.py", line 265, in _reconstruct
    y = func(*args)
  File "/usr/lib/python3.10/copy.py", line 264, in <genexpr>
    args = (deepcopy(arg, memo) for arg in args)
  ...
RecursionError: maximum recursion depth exceeded  

---

This change is 

[xpconanfan]

Reviewable status: 0 of 1 files reviewed, 1 unresolved discussion (waiting on @uael)

---

mobly/records.py line 280 at r1 (raw file):

    try:
      exception = copy.deepcopy(self.exception)
    except (TypeError, RecursionError):

can you share the data that cause this to be raised?
I'm not sure if the same logic is correct for handling RecursionError, so let's take a look at the root cause to be sure

Also, we should have unit tests to cover this case :)

[uael]

After some more investigation here is what's going on.

The AioRpcError from grpcio has what I see has a bogus initialization by passing self to the base constructor which actually create a self recursive exception:

python/grpcio/grpc/aio/_call.py:89

    def __init__(self, ...):
        super().__init__(self)

The RecursionError would have been raised here if __str__ was not overridden:

mobly/records.py:248

    else:
      self._set_details(e)

It's raising in the deepcopy instead:

mobly/records.py:279

    try:
      exception = copy.deepcopy(self.exception)
    except TypeError:

Even if the recursion is clearly a bug in grpcio (I'm gonna open PR for it), since nothing prevent an error to be recursive, I still think this change to be relevant.

I'm not sure if the same logic is correct for handling RecursionError

I think using the exception as is fine too since it cannot be copied.

I also just added a specific unit test.
Here is the pytest trace of the added test without the fix:

======================================================================================================================================== FAILURES ========================================================================================================================================
__________________________________________________________________________________________________________________ RecordsTest.test_recursive_exception_record_deepcopy __________________________________________________________________________________________________________________

self = <tests.mobly.records_test.RecordsTest testMethod=test_recursive_exception_record_deepcopy>

    def test_recursive_exception_record_deepcopy(self):
      """Makes sure ExceptionRecord wrapper handles deep copy properly in case of recursive exception."""
      try:
        raise RecordTestRecursiveError()
      except RecordTestRecursiveError as e:
        er = records.ExceptionRecord(e)
>     new_er = copy.deepcopy(er)

tests/mobly/records_test.py:450: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
/usr/lib/python3.10/copy.py:153: in deepcopy
    y = copier(memo)
mobly/records.py:279: in __deepcopy__
    exception = copy.deepcopy(self.exception)
/usr/lib/python3.10/copy.py:172: in deepcopy
    y = _reconstruct(x, memo, *rv)
/usr/lib/python3.10/copy.py:265: in _reconstruct
    y = func(*args)
/usr/lib/python3.10/copy.py:264: in <genexpr>
    args = (deepcopy(arg, memo) for arg in args)
/usr/lib/python3.10/copy.py:172: in deepcopy
    y = _reconstruct(x, memo, *rv)
E   RecursionError: maximum recursion depth exceeded while calling a Python object
!!! Recursion detected (same locals & position)

[uael]

Reviewable status: 0 of 2 files reviewed, 2 unresolved discussions (waiting on @uael and @xpconanfan)

---

mobly/records.py line 280 at r1 (raw file):

Previously, xpconanfan (Ang Li) wrote…

can you share the data that cause this to be raised?
I'm not sure if the same logic is correct for handling RecursionError, so let's take a look at the root cause to be sure

Also, we should have unit tests to cover this case :)

Done.

---

tests/mobly/records_test.py line 444 at r2 (raw file):

Previously, xpconanfan (Ang Li) wrote…

pls make sure the line stays within line length limit of 80 chars

Done.