json.dumps no longer works directly with benedict in 0.20.0 about python-benedict HOT 7 CLOSED

@simkimsia thank you for reporting this. 
I guess this problem is not related to casting, but to the fact that to keep the pointer to the input dict benedict now stores data inside a wrapped dict -> https://github.com/fabiocaccamo/python-benedict/blob/master/benedict/dicts/base/base_dict.py

This should be a completely backward compatibility and transparent behavior.
In case of emergency, there is a new dict() method to access the wrapped dict, so you could just do:

normal_dict = {'list': {'scope': {'pk': '109'}}
benedict_dict = benedict(normal_dict)

instance = SomeModel.objects.create(linkage=benedict_dict.dict())
retrieved = SomeModel.objects.last()

In any case this is just a workaround, and casting benedict to dict should work fine.

def test_cast_benedict_to_dict(self):
    b = benedict({
        'a': 1,
        'b': {
            'c': {
                'd': 2,
            },
        },
    })
    d = dict(b)
    self.assertTrue(isinstance(d, dict))
    self.assertEqual(type(d), dict)
    self.assertTrue(b == d)
    self.assertFalse(b is d)

It's my intention to keep benedict 100% dict compatible, so we must understand what breaks the django JSONField behavior to fix it.

Could you debug better the cause of this problem?

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Thank you for prompt reply

@fabiocaccamo

I try but no promises as this is not high on priority once I have a workaround

Hope you understand

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@fabiocaccamo

I think I found the cause.

THis is my code to replicate the error using pytest 3.4.1

import json

from benedict import benedict


"""
doc_string for test_python_class
"""


class TestBenedict:
    """
    doc_string
    """

    def teardown_method(self, test_method):
        pass

    def test_cast_benedict_to_dict(self):
        """
        some doc string
        """
        b = benedict({
            'a': 1,
            'b': {
                'c': {
                    'd': 2,
                },
            },
        })
        d = dict(b)
        assert isinstance(d, dict)
        assert type(d) == dict
        assert b == d
        assert b is not d

    def test_json_dumps_benedict(self):
        """
        some doc string
        """
        b = benedict({
            'a': 1,
            'b': {
                'c': {
                    'd': 2,
                },
            },
        })
        dumped = json.dumps(b)
        print(dumped)
        assert isinstance(dumped, str)
        assert dumped == '{"a": 1, "b": {"c": {"d": 2}}}'

This is the 0.20.0 effort when I run pytest test_benedict.py -s

This is the 0.19.0 effort when I run the same command and same test code

Sorry I know the best way is to create a PR and write a failing test, but I am not sure how to do that in your current setup.

So it was easier for me to write a failing test as a standalone.

Perhaps you can advise in documentation on how to write failing tests as PR.

Long story of the cause

JSONField uses an encoder for the dumping of the json input. The default encoder comes from psycopg2 which by default simply uses json.dumps at this line https://github.com/psycopg/psycopg2/blob/e50f3129c25aa764b3acb6205f515bab56c3f6d2/lib/_json.py#L59

Hence I wrote a test to test that json.dumps works for 0.19 but fails for 0.20. The test is a success as shown above.

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@simkimsia the dict() method is used internally and if someone needs to use it, it means that there is some problem, so I intentionally omitted it from the README.

Thank you very much for the test, it's very useful!

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I confirm this works ✅

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@simkimsia don't worry, if you find the time, just check what is called by the JSONField.

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if you find the time, just check what is called by the JSONField.

Yes, I will try to do so.

By the way, I see that you made no commits. Yet you cite a method .dict() as workaround I don't find in the readme.

Am I mistaken?

Update

Ok I see it in the BaseDict class https://github.com/fabiocaccamo/python-benedict/blob/master/benedict/dicts/base/base_dict.py#L51 Perhaps would be useful to update the README? I leave that to you. Looks like I chose a convoluted way to export back to regular dict in my own workaround

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