Assert that Serializer was initialized with data=something in is_valid()

[loic]

>>> serializer = SnippetSerializer(snippet)
>>> serializer.is_valid()
False
>>> serializer.errors
Traceback (most recent call last):
  File "<console>", line 1, in <module>
  File "/Users/loic/Dev/django-rest-framework/rest_framework/serializers.py", line 429, in errors
    return ReturnDict(ret, serializer=self)
  File "/Users/loic/Dev/django-rest-framework/rest_framework/utils/serializer_helpers.py", line 13, in __init__
    super(ReturnDict, self).__init__(*args, **kwargs)
  File "/usr/local/Cellar/python/2.7.8_2/Frameworks/Python.framework/Versions/2.7/lib/python2.7/collections.py", line 52, in __init__
    self.__update(*args, **kwds)
  File "/Users/loic/Dev/rest_tutorial/./.venv/bin/../lib/python2.7/_abcoll.py", line 566, in update
    for key, value in other:
ValueError: too many values to unpack

[vccabral]

@loic, how are you doing that from the interpreter shell when testing the docs? Are you going through the process of setting up the snippet code? Just wondering to see if you have a github project I can clone to try and recreate this issue.

[xordoquy]

You need to instantiate your serializer with data=snippet, otherwise it is assumed to be an instance, not data.

>>> from snippets.serializers import SnippetSerializer
>>> s = SnippetSerializer({'title': 'something'})
>>> s.is_valid()
False
>>> s.errors
Traceback (most recent call last):
  File "<console>", line 1, in <module>
  File "/Users/xordoquy/.virtualenvs/test/lib/python3.4/site-packages/rest_framework/serializers.py", line 426, in errors
    return ReturnDict(ret, serializer=self)
  File "/Users/xordoquy/.virtualenvs/test/lib/python3.4/site-packages/rest_framework/utils/serializer_helpers.py", line 12, in __init__
    super(ReturnDict, self).__init__(*args, **kwargs)
  File "/Users/xordoquy/.virtualenvs/test/lib/python3.4/collections/__init__.py", line 56, in __init__
    self.__update(*args, **kwds)
  File "/Users/xordoquy/.virtualenvs/test/bin/../lib/python3.4/_collections_abc.py", line 602, in update
    for key, value in other:
ValueError: too many values to unpack (expected 2)
>>> s = SnippetSerializer(data={'title': 'something'})
>>> s.is_valid()
False
>>> s.errors
ReturnDict([('code', ['This field is required.'])])
>>> 

[loic]

@vccabral I used the model and serializer from the tutorial part 1. Obviously the docs don't recommend to do this, I was just experimenting.

@xordoquy sorry if I wasn't clear, this is an enhancement proposal, not a bug report. I propose that is_valid() raises an error when data is missing.

This was discussed a few days ago on IRC:

loic84: tomchristie: SnippetSerializer(snippet).is_valid() is that supposed to work? or is_valid() should only be called when there is data?
loic84: data as in SnippetSerializer(data=data)
tomchristie: loic84: Really `is_valid()` should raise an assertion error if you call it without having passed `data=...`
tomchristie: It's doesn't yet, tho

[vccabral]

@loic what is the "django-rest-framework" unit test way to do an self.assertRaises?

https://docs.python.org/2/library/unittest.html

[xordoquy]

@vccabral we are using py.test so http://pytest.org/latest/assert.html#assertions-about-expected-exceptions
Please also note that py.test works well with unit test's assert* - not sure we started to clean them.

[vccabral]

@xordoquy thanks!

[vccabral]

If I read the issue correctly this might be the fix. @loic @xordoquy any feedback is appreciated.

#2234

[tomchristie]

Thanks for your work on this! Based on this, and the issues noted in #2276, #2284 I've issued pull request #2291 which superseeds this one. Thanks for getting things rolling!