Django forms.FileField(required=True) 如果为空则通过验证

Question

我有一个带有必需文件字段的 Django 表单(不是 ModelForm)。根据the FileField documentation ，FileField 的验证应该验证非空文件数据是否已绑定(bind)到表单，但我没有看到这种行为。相反，我可以在没有文件的情况下提交表单，并且表单通过验证。预期的行为是验证失败。

当在表单中指定文件时，事情会按预期工作。

我的表单看起来像这样:

class BucketUploadForm(forms.Form):
  file = forms.FileField(required=True)  # required=True is the default, but I'm being explicit

  def clean(self):
    upload_to = '/some/path'
    upload_to += self.cleaned_data['file'].name  # this is raising a KeyError

我的观点看起来像这样:

def bucket_upload(request):
  if request.method == 'POST':
    form = BucketUploadForm(request.POST, request.FILES)
    if form.is_valid():  # this is raising the aforementioned KeyError when no file is submitted
      do_stuff()
      return HttpResponseRedirect(some_url)
    else:
      form = BucketUploadForm(initial=request.GET)
    return render_to_response('handin/bucket_upload.html', {'form': form}, context_instance=RequestContext(request))

我的模板看起来像这样:

<form action="" method="post" enctype="multipart/form-data">
{% csrf_token %}
<table>
{{ form }}
</table>
<input type="submit" value="Upload" />
</form>

回溯看起来像这样:

Django Version: 1.3.1
Python Version: 2.7.3
Installed Applications:
['django.contrib.auth',
 'django.contrib.contenttypes',
 'django.contrib.sessions',
 'django.contrib.sites',
 'django.contrib.messages',
 'django.contrib.staticfiles',
 'django.contrib.admin',
 'django.contrib.admindocs',
 'hgrepo',
 'sshkey',
 'handin',
 'accounts']
Installed Middleware:
('django.middleware.common.CommonMiddleware',
 'django.contrib.sessions.middleware.SessionMiddleware',
 'django.middleware.csrf.CsrfViewMiddleware',
 'django.contrib.auth.middleware.AuthenticationMiddleware',
 'django.contrib.messages.middleware.MessageMiddleware')


Traceback:
File "/usr/lib/python2.7/dist-packages/django/core/handlers/base.py" in get_response
  111.                         response = callback(request, *callback_args, **callback_kwargs)
File "/usr/lib/python2.7/dist-packages/django/contrib/auth/decorators.py" in _wrapped_view
  23.                 return view_func(request, *args, **kwargs)
File "/usr/lib/python2.7/dist-packages/django/views/decorators/http.py" in inner
  45.             return func(request, *args, **kwargs)
File "/home/sduckwo/projects/webhandin/webhandin/handin/views.py" in bucket_upload
  461.     if form.is_valid():
File "/usr/lib/python2.7/dist-packages/django/forms/forms.py" in is_valid
  121.         return self.is_bound and not bool(self.errors)
File "/usr/lib/python2.7/dist-packages/django/forms/forms.py" in _get_errors
  112.             self.full_clean()
File "/usr/lib/python2.7/dist-packages/django/forms/forms.py" in full_clean
  268.         self._clean_form()
File "/usr/lib/python2.7/dist-packages/django/forms/forms.py" in _clean_form
  296.             self.cleaned_data = self.clean()
File "/home/sduckwo/projects/webhandin/webhandin/handin/forms.py" in clean
  116.       upload_to += self.cleaned_data['file'].name

Exception Type: KeyError at /courses/a/b/assignments/c/sduckwo/upload
Exception Value: 'file'

更新

从 BucketUploadForm 中删除 clean 方法会导致 FileField 的验证按预期失败。但是，我需要 clean 方法来进行其他检查，因此无法永久删除它。

我还发现，通过将 clean 方法修改为如下所示:

class BucketUploadForm(forms.Form):
  file = forms.FileField(required=True)  # required=True is the default, but I'm being explicit

  def clean(self):
    if 'file' not in self.cleaned_data:
      raise ValidationError('No file or empty file given')
    upload_to = '/some/path'
    upload_to += self.cleaned_data['file'].name  # this is raising a KeyError

然后验证按预期失败，但我收到两条错误消息:

1. “没有给出文件或空文件”，由 BucketUploadForm.clean() 引发
2. “此字段是必需的”，由 FileField.clean() 引发，这就是我最初想要的。

这告诉我 FileField.clean() 正在引发 ValidationError，但该异常会以某种方式被忽略，除非 BucketUploadForm.clean() 不存在或也引发 ValidationError。

所以现在我可能更接近我的最终目标，但仍然很困惑。

Answer 1

我想我以前见过这个。从轶事经验来看，如果缺少字段，Django 似乎不会停止验证(例如，即使缺少必填字段，它也会调用 clean() )。它表示由于未在 clean_data 中包含字段名称而缺少必填字段。

斯科特指出它是 documented here :

For any field, if the Field.clean() method raises a ValidationError, any field-specific cleaning method is not called. However, the cleaning methods for all remaining fields are still executed.

因此，我认为解决方案只是通过检查“file”键是否在cleaned_data中来防御性地对clean()方法进行编程，如果不是，则按原样返回cleaned_data。 Django 已经知道缺少必需的字段，因此 is_valid() 将失败并且不会造成任何损害。

def clean(self):
  upload_to = '/some/path'
  if not 'file' in self.cleaned_data:
    return self.cleaned_data
  upload_to += self.cleaned_data['file'].name