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Changes to ImageFileDescriptor and ImageField to fix a few cases of setting image dimension fields.

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* Moved dimension field update logic out of `ImageFileDescriptor.__set__` and into its own method on `ImageField`.
 * New `ImageField.update_dimension_fields` method is attached to model instance's `post_init` signal so that:
   * Dimension fields are set when defined before the ImageField.
   * Dimension fields are set when the field is assigned in the model constructor (fixes #11196), but only if the dimension fields don't already have values, so we avoid updating the dimensions every time an object is loaded from the database (fixes #11084).
 * Clear dimension fields when the ImageField is set to None, which also causes dimension fields to be cleared when `ImageFieldFile.delete()` is used.
 * Added many more tests for ImageField that test edge cases we weren't testing before, and moved the ImageField tests out of `file_storage` and into their own module within `model_fields`.


git-svn-id: http://code.djangoproject.com/svn/django/trunk@10858 bcc190cf-cafb-0310-a4f2-bffc1f526a37
This commit is contained in:
Gary Wilson Jr 2009-05-28 05:46:09 +00:00
parent 7638651cc3
commit d89ba464dd
8 changed files with 621 additions and 152 deletions
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133
django/db/models/fields/files.py
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@ -142,13 +142,13 @@ class FileDescriptor(object):
"""
The descriptor for the file attribute on the model instance. Returns a
FieldFile when accessed so you can do stuff like::
>>> instance.file.size
Assigns a file object on assignment so you can do::
>>> instance.file = File(...)
"""
def __init__(self, field):
self.field = field
@ -156,9 +156,9 @@ class FileDescriptor(object):
def __get__(self, instance=None, owner=None):
if instance is None:
raise AttributeError(
"The '%s' attribute can only be accessed from %s instances."
"The '%s' attribute can only be accessed from %s instances."
% (self.field.name, owner.__name__))
# This is slightly complicated, so worth an explanation.
# instance.file`needs to ultimately return some instance of `File`,
# probably a subclass. Additionally, this returned object needs to have
@ -168,8 +168,8 @@ class FileDescriptor(object):
# peek below you can see that we're not. So depending on the current
# value of the field we have to dynamically construct some sort of
# "thing" to return.
# The instance dict contains whatever was originally assigned
# The instance dict contains whatever was originally assigned
# in __set__.
file = instance.__dict__[self.field.name]
@ -186,14 +186,14 @@ class FileDescriptor(object):
# Other types of files may be assigned as well, but they need to have
# the FieldFile interface added to the. Thus, we wrap any other type of
# File inside a FieldFile (well, the field's attr_class, which is
# File inside a FieldFile (well, the field's attr_class, which is
# usually FieldFile).
elif isinstance(file, File) and not isinstance(file, FieldFile):
file_copy = self.field.attr_class(instance, self.field, file.name)
file_copy.file = file
file_copy._committed = False
instance.__dict__[self.field.name] = file_copy
# Finally, because of the (some would say boneheaded) way pickle works,
# the underlying FieldFile might not actually itself have an associated
# file. So we need to reset the details of the FieldFile in those cases.
@ -201,7 +201,7 @@ class FileDescriptor(object):
file.instance = instance
file.field = self.field
file.storage = self.field.storage
# That was fun, wasn't it?
return instance.__dict__[self.field.name]
@ -212,7 +212,7 @@ class FileField(Field):
# The class to wrap instance attributes in. Accessing the file object off
# the instance will always return an instance of attr_class.
attr_class = FieldFile
# The descriptor to use for accessing the attribute off of the class.
descriptor_class = FileDescriptor
@ -300,40 +300,20 @@ class ImageFileDescriptor(FileDescriptor):
assigning the width/height to the width_field/height_field, if appropriate.
"""
def __set__(self, instance, value):
previous_file = instance.__dict__.get(self.field.name)
super(ImageFileDescriptor, self).__set__(instance, value)
# The rest of this method deals with width/height fields, so we can
# bail early if neither is used.
if not self.field.width_field and not self.field.height_field:
return
# We need to call the descriptor's __get__ to coerce this assigned
# value into an instance of the right type (an ImageFieldFile, in this
# case).
value = self.__get__(instance)
if not value:
return
# Get the image dimensions, making sure to leave the file in the same
# state (opened or closed) that we got it in. However, we *don't* rewind
# the file pointer if the file is already open. This is in keeping with
# most Python standard library file operations that leave it up to the
# user code to reset file pointers after operations that move it.
from django.core.files.images import get_image_dimensions
close = value.closed
value.open()
try:
width, height = get_image_dimensions(value)
finally:
if close:
value.close()
# Update the width and height fields
if self.field.width_field:
setattr(value.instance, self.field.width_field, width)
if self.field.height_field:
setattr(value.instance, self.field.height_field, height)
# To prevent recalculating image dimensions when we are instantiating
# an object from the database (bug #11084), only update dimensions if
# the field had a value before this assignment. Since the default
# value for FileField subclasses is an instance of field.attr_class,
# previous_file will only be None when we are called from
# Model.__init__(). The ImageField.update_dimension_fields method
# hooked up to the post_init signal handles the Model.__init__() cases.
# Assignment happening outside of Model.__init__() will trigger the
# update right here.
if previous_file is not None:
self.field.update_dimension_fields(instance, force=True)
class ImageFieldFile(ImageFile, FieldFile):
def delete(self, save=True):
@ -350,6 +330,69 @@ class ImageField(FileField):
self.width_field, self.height_field = width_field, height_field
FileField.__init__(self, verbose_name, name, **kwargs)
def contribute_to_class(self, cls, name):
super(ImageField, self).contribute_to_class(cls, name)
# Attach update_dimension_fields so that dimension fields declared
# after their corresponding image field don't stay cleared by
# Model.__init__, see bug #11196.
signals.post_init.connect(self.update_dimension_fields, sender=cls)
def update_dimension_fields(self, instance, force=False, *args, **kwargs):
"""
Updates field's width and height fields, if defined.
This method is hooked up to model's post_init signal to update
dimensions after instantiating a model instance. However, dimensions
won't be updated if the dimensions fields are already populated. This
avoids unnecessary recalculation when loading an object from the
database.
Dimensions can be forced to update with force=True, which is how
ImageFileDescriptor.__set__ calls this method.
"""
# Nothing to update if the field doesn't have have dimension fields.
has_dimension_fields = self.width_field or self.height_field
if not has_dimension_fields:
return
# getattr will call the ImageFileDescriptor's __get__ method, which
# coerces the assigned value into an instance of self.attr_class
# (ImageFieldFile in this case).
file = getattr(instance, self.attname)
# Nothing to update if we have no file and not being forced to update.
if not file and not force:
return
dimension_fields_filled = not(
(self.width_field and not getattr(instance, self.width_field))
or (self.height_field and not getattr(instance, self.height_field))
)
# When both dimension fields have values, we are most likely loading
# data from the database or updating an image field that already had
# an image stored. In the first case, we don't want to update the
# dimension fields because we are already getting their values from the
# database. In the second case, we do want to update the dimensions
# fields and will skip this return because force will be True since we
# were called from ImageFileDescriptor.__set__.
if dimension_fields_filled and not force:
return
# file should be an instance of ImageFieldFile or should be None.
if file:
width = file.width
height = file.height
else:
# No file, so clear dimensions fields.
width = None
height = None
# Update the width and height fields.
if self.width_field:
setattr(instance, self.width_field, width)
if self.height_field:
setattr(instance, self.height_field, height)
def formfield(self, **kwargs):
defaults = {'form_class': forms.ImageField}
defaults.update(kwargs)