Re: [Django] #23222: Empty BinaryField != b'' on Python 2

[Django]

#23222: Empty BinaryField != b'' on Python 2
-+-
 Reporter:  wkschwartz@… |Owner:  Grzegorz
 |  Ślusarek
 Type:  Bug  |   Status:  closed
Component:  Database layer   |  Version:  master
  (models, ORM)  |
 Severity:  Normal   |   Resolution:  wontfix
 Keywords:  py2  | Triage Stage:  Accepted
Has patch:  0|  Needs documentation:  0
  Needs tests:  0|  Patch needs improvement:  0
Easy pickings:  0|UI/UX:  0
-+-
Changes (by Tim Graham):

 * status:  assigned => closed
 * resolution:   => wontfix


Comment:

 Closing due to the end of Python 2 support in master in a couple weeks.

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Re: [Django] #23222: Empty BinaryField != b'' on Python 2

[Django]

#23222: Empty BinaryField != b'' on Python 2
-+-
 Reporter:  wkschwartz@… |Owner:  gregorth
 Type:  Bug  |   Status:  assigned
Component:  Database layer   |  Version:  master
  (models, ORM)  |
 Severity:  Normal   |   Resolution:
 Keywords:  py2  | Triage Stage:  Accepted
Has patch:  0|  Needs documentation:  0
  Needs tests:  0|  Patch needs improvement:  0
Easy pickings:  0|UI/UX:  0
-+-
Changes (by timgraham):

 * keywords:   => py2


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Re: [Django] #23222: Empty BinaryField != b'' on Python 2

[Django]

#23222: Empty BinaryField != b'' on Python 2
-+-
 Reporter:  wkschwartz@… |Owner:  gregorth
 Type:  Bug  |   Status:  assigned
Component:  Database layer   |  Version:  master
  (models, ORM)  |
 Severity:  Normal   |   Resolution:
 Keywords:   | Triage Stage:  Accepted
Has patch:  0|  Needs documentation:  0
  Needs tests:  0|  Patch needs improvement:  0
Easy pickings:  0|UI/UX:  0
-+-
Description changed by wkschwartz:

Old description:

> = Problem =
>
> In Python 2, at least under SQLite, the initial value for an empty binary
> field behaves inconsistently. The ORM thinks it's an empty `bytes`:
> `b''`. The database connection manager thinks it's a buffer. Now, the
> buffer evaluates to `False` and has zero length. So it'll mostly work.
> But not always -- and most importantly to me, not in my unit tests!
>
> See http://stackoverflow.com/q/12625557/1286628
>
> Note this was not a problem under Python 3.4.
>
> = Steps to Reproduce =
>
> Using Python 2.7.8, SQLite, and either Django 1.7rc2 or Django @
> edcc75e5ac5b9dc2f174580e7adacd3be586f8bd (HEAD at the time of this
> writing; the error exists in both places)
>
> 1. Make a new project and a new app and add the app to settings.py
> 2. Fill in `app/models.py` as follows
>
> {{{#!python
> from django.db import models
> class BinModel(models.Model):
> data = models.BinaryField()
> }}}
>
> 3. Run from the command line:
>
> {{{#!bash
> (venv) $ ./manage.py makemigrations app ./manage.py migrate &&
> ./manage.py shell
> }}}
>
> 4. Run from the resulting Python shell
>
> {{{#!python
> >>> from app import models; m = models.BinModel(); m.save(); n =
> models.BinModel.objects.get()
> >>> m.data
> ''
> >>> m.data == b''
> True
> >>> n.data
> 
> >>> n.data == b''
> False
> >>> bool(n.data)
> False
> >>> len(n.data)
> 0
> >>> bytes(n.data)
> ''
> }}}
>
> Note that the same problem persisted when I had a default value for the
> field. There was no problem under Python 3.4.

New description:

 = Problem =

 In Python 2, at least under SQLite, the initial value for an empty binary
 field behaves inconsistently. The ORM thinks it's an empty `bytes`: `b''`.
 The database connection manager thinks it's a buffer. Now, the buffer
 evaluates to `False` and has zero length. So it'll mostly work. But not
 always -- and most importantly to me, not in my unit tests!

 See http://stackoverflow.com/q/12625557/1286628

 Note this was not a problem under Python 3.4.

 = Steps to Reproduce =

 Using Python 2.7.8, SQLite, and either Django 1.7rc2 or Django @
 edcc75e5ac5b9dc2f174580e7adacd3be586f8bd (HEAD at the time of this
 writing; the error exists in both places)

 1. Make a new project and a new app and add the app to settings.py
 2. Fill in `app/models.py` as follows

 {{{#!python
 from django.db import models
 class BinModel(models.Model):
 data = models.BinaryField()
 }}}

 3. Run from the command line:

 {{{#!bash
 (venv) $ ./manage.py makemigrations app && ./manage.py migrate &&
 ./manage.py shell
 }}}

 4. Run from the resulting Python shell

 {{{#!python
 >>> from app import models; m = models.BinModel(); m.save(); n =
 models.BinModel.objects.get()
 >>> m.data
 ''
 >>> m.data == b''
 True
 >>> n.data
 
 >>> n.data == b''
 False
 >>> bool(n.data)
 False
 >>> len(n.data)
 0
 >>> bytes(n.data)
 ''
 }}}

 Note that the same problem persisted when I had a default value for the
 field. There was no problem under Python 3.4.

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Re: [Django] #23222: Empty BinaryField != b'' on Python 2

[Django]

#23222: Empty BinaryField != b'' on Python 2
-+-
 Reporter:  wkschwartz@… |Owner:  gregorth
 Type:  Bug  |   Status:  assigned
Component:  Database layer   |  Version:  master
  (models, ORM)  |
 Severity:  Normal   |   Resolution:
 Keywords:   | Triage Stage:  Accepted
Has patch:  0|  Needs documentation:  0
  Needs tests:  0|  Patch needs improvement:  0
Easy pickings:  0|UI/UX:  0
-+-
Changes (by gregorth):

 * status:  new => assigned
 * owner:  nobody => gregorth


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Re: [Django] #23222: Empty BinaryField != b'' on Python 2

[Django]

#23222: Empty BinaryField != b'' on Python 2
-+-
 Reporter:  wkschwartz@… |Owner:  nobody
 Type:  Bug  |   Status:  new
Component:  Database layer   |  Version:  master
  (models, ORM)  |
 Severity:  Normal   |   Resolution:
 Keywords:   | Triage Stage:  Accepted
Has patch:  0|  Needs documentation:  0
  Needs tests:  0|  Patch needs improvement:  0
Easy pickings:  0|UI/UX:  0
-+-

Comment (by raully7):

 I'm not sure, if it's only a problem with empty Empty BinaryField.

 I try to add a test function in model_fields.tests.BinaryFieldTests, as
 below:

 {{{
 def test_retrieve_compare_non_empty_field(self):
 dm = DataModel(data=b'test')
 self.assertTrue(dm.data == b'test')
 dm.save()
 dm = DataModel.objects.get(pk=dm.pk)
 self.assertTrue(dm.data == b'test')
 }}}

 On python2, the first assertion will be passed, and the second one will be
 failed.

 As the data field is a buffer type after retrieving, we can't do a simple
 compare.

 We can see the definition:

 {{{
 class BinaryField(Field):
 ...
 def get_db_prep_value(self, value, connection, prepared=False):
 value = super(BinaryField, self).get_db_prep_value(value,
 connection, prepared)
 if value is not None:
 return connection.Database.Binary(value)
 return value
 }}}

 I can't go further as I know little about six, and hope this can help:)

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Re: [Django] #23222: Empty BinaryField != b'' on Python 2

[Django]

#23222: Empty BinaryField != b'' on Python 2
-+-
 Reporter:  wkschwartz@… |Owner:  nobody
 Type:  Bug  |   Status:  new
Component:  Database layer   |  Version:  master
  (models, ORM)  |   Resolution:
 Severity:  Normal   | Triage Stage:  Accepted
 Keywords:   |  Needs documentation:  0
Has patch:  0|  Patch needs improvement:  0
  Needs tests:  0|UI/UX:  0
Easy pickings:  0|
-+-
Changes (by bmispelon):

 * stage:  Unreviewed => Accepted


Comment:

 Marking this as accepted per previous comments.

 This seem like it might be caused by six using buffers on python 2 [1].

 Thanks.

 [1] https://github.com/django/django/blob/master/django/utils/six.py#L681

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Re: [Django] #23222: Empty BinaryField != b'' on Python 2 (was: Empty BinaryField != b'' in Python 2/SQLite)

[Django]

#23222: Empty BinaryField != b'' on Python 2
-+-
 Reporter:  wkschwartz@… |Owner:  nobody
 Type:  Bug  |   Status:  new
Component:  Database layer   |  Version:  master
  (models, ORM)  |   Resolution:
 Severity:  Normal   | Triage Stage:
 Keywords:   |  Unreviewed
Has patch:  0|  Needs documentation:  0
  Needs tests:  0|  Patch needs improvement:  0
Easy pickings:  0|UI/UX:  0
-+-

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