142 lines
4.8 KiB
Python
142 lines
4.8 KiB
Python
"""
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This module collects helper functions and classes that "span" multiple levels
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of MVC. In other words, these functions/classes introduce controlled coupling
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for convenience's sake.
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"""
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from django.http import (
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Http404, HttpResponse, HttpResponsePermanentRedirect, HttpResponseRedirect,
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)
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from django.template import loader
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from django.urls import NoReverseMatch, reverse
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from django.utils.functional import Promise
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def render(request, template_name, context=None, content_type=None, status=None, using=None):
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"""
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Return a HttpResponse whose content is filled with the result of calling
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django.template.loader.render_to_string() with the passed arguments.
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"""
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content = loader.render_to_string(template_name, context, request, using=using)
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return HttpResponse(content, content_type, status)
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def redirect(to, *args, permanent=False, **kwargs):
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"""
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Return an HttpResponseRedirect to the appropriate URL for the arguments
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passed.
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The arguments could be:
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* A model: the model's `get_absolute_url()` function will be called.
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* A view name, possibly with arguments: `urls.reverse()` will be used
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to reverse-resolve the name.
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* A URL, which will be used as-is for the redirect location.
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Issues a temporary redirect by default; pass permanent=True to issue a
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permanent redirect.
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"""
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redirect_class = HttpResponsePermanentRedirect if permanent else HttpResponseRedirect
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return redirect_class(resolve_url(to, *args, **kwargs))
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def _get_queryset(klass):
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"""
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Return a QuerySet or a Manager.
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Duck typing in action: any class with a `get()` method (for
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get_object_or_404) or a `filter()` method (for get_list_or_404) might do
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the job.
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"""
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# If it is a model class or anything else with ._default_manager
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if hasattr(klass, '_default_manager'):
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return klass._default_manager.all()
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return klass
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def get_object_or_404(klass, *args, **kwargs):
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"""
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Use get() to return an object, or raise a Http404 exception if the object
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does not exist.
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klass may be a Model, Manager, or QuerySet object. All other passed
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arguments and keyword arguments are used in the get() query.
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Like with QuerySet.get(), MultipleObjectsReturned is raised if more than
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one object is found.
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"""
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queryset = _get_queryset(klass)
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if not hasattr(queryset, 'get'):
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klass__name = klass.__name__ if isinstance(klass, type) else klass.__class__.__name__
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raise ValueError(
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"First argument to get_object_or_404() must be a Model, Manager, "
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"or QuerySet, not '%s'." % klass__name
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)
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try:
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return queryset.get(*args, **kwargs)
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except queryset.model.DoesNotExist:
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raise Http404('No %s matches the given query.' % queryset.model._meta.object_name)
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def get_list_or_404(klass, *args, **kwargs):
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"""
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Use filter() to return a list of objects, or raise a Http404 exception if
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the list is empty.
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klass may be a Model, Manager, or QuerySet object. All other passed
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arguments and keyword arguments are used in the filter() query.
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"""
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queryset = _get_queryset(klass)
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if not hasattr(queryset, 'filter'):
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klass__name = klass.__name__ if isinstance(klass, type) else klass.__class__.__name__
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raise ValueError(
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"First argument to get_list_or_404() must be a Model, Manager, or "
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"QuerySet, not '%s'." % klass__name
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)
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obj_list = list(queryset.filter(*args, **kwargs))
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if not obj_list:
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raise Http404('No %s matches the given query.' % queryset.model._meta.object_name)
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return obj_list
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def resolve_url(to, *args, **kwargs):
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"""
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Return a URL appropriate for the arguments passed.
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The arguments could be:
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* A model: the model's `get_absolute_url()` function will be called.
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* A view name, possibly with arguments: `urls.reverse()` will be used
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to reverse-resolve the name.
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* A URL, which will be returned as-is.
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"""
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# If it's a model, use get_absolute_url()
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if hasattr(to, 'get_absolute_url'):
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return to.get_absolute_url()
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if isinstance(to, Promise):
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# Expand the lazy instance, as it can cause issues when it is passed
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# further to some Python functions like urlparse.
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to = str(to)
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if isinstance(to, str):
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# Handle relative URLs
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if to.startswith(('./', '../')):
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return to
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# Next try a reverse URL resolution.
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try:
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return reverse(to, args=args, kwargs=kwargs)
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except NoReverseMatch:
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# If this is a callable, re-raise.
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if callable(to):
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raise
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# If this doesn't "feel" like a URL, re-raise.
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if '/' not in to and '.' not in to:
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raise
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# Finally, fall back and assume it's a URL
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return to
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