templatetags/embed.py

   1 from django import template
   2 from django.contrib.contenttypes.models import ContentType
   3 from django.conf import settings
   4 from django.template.loader_tags import ExtendsNode, BlockContext, BLOCK_CONTEXT_KEY, TextNode, BlockNode
   5 from philo.utils import LOADED_TEMPLATE_ATTR
   6
   7
   8 register = template.Library()
   9 EMBED_CONTEXT_KEY = 'embed_context'
  10
  11
  12 class EmbedContext(object):
  13         "Inspired by django.template.loader_tags.BlockContext."
  14         def __init__(self):
  15                 self.embeds = {}
  16                 self.rendered = []
  17
  18         def add_embeds(self, embeds):
  19                 for content_type, embed_list in embeds.iteritems():
  20                         if content_type in self.embeds:
  21                                 self.embeds[content_type] = embed_list + self.embeds[content_type]
  22                         else:
  23                                 self.embeds[content_type] = embed_list
  24
  25         def get_embed_template(self, embed, context):
  26                 """To return a template for an embed node, find the node's position in the stack
  27                 and then progress up the stack until a template-defining node is found
  28                 """
  29                 ct = embed.get_content_type(context)
  30                 embeds = self.embeds[ct]
  31                 embeds = embeds[:embeds.index(embed)][::-1]
  32                 for e in embeds:
  33                         template = e.get_template(context)
  34                         if template:
  35                                 return template
  36
  37                 # No template was found in the current render_context - but perhaps one level up? Or more?
  38                 # We may be in an inclusion tag.
  39                 self_found = False
  40                 for context_dict in context.render_context.dicts[::-1]:
  41                         if not self_found:
  42                                 if self in context_dict.values():
  43                                         self_found = True
  44                                         continue
  45                         elif EMBED_CONTEXT_KEY not in context_dict:
  46                                 continue
  47                         else:
  48                                 embed_context = context_dict[EMBED_CONTEXT_KEY]
  49                                 # We can tell where we are in the list of embeds by which have already been rendered.
  50                                 embeds = embed_context.embeds[ct][:len(embed_context.rendered)][::-1]
  51                                 for e in embeds:
  52                                         template = e.get_template(context)
  53                                         if template:
  54                                                 return template
  55
  56                 raise IndexError
  57
  58
  59 # Override ExtendsNode render method to have it handle EmbedNodes
  60 # similarly to BlockNodes.
  61 old_extends_node_init = ExtendsNode.__init__
  62
  63
  64 def get_embed_dict(embed_list, context):
  65         embeds = {}
  66         for e in embed_list:
  67                 ct = e.get_content_type(context)
  68                 if ct is None:
  69                         # Then the embed doesn't exist for this context.
  70                         continue
  71                 if ct not in embeds:
  72                         embeds[ct] = [e]
  73                 else:
  74                         embeds[ct].append(e)
  75         return embeds
  76
  77
  78 def extends_node_init(self, nodelist, *args, **kwargs):
  79         self.embed_list = nodelist.get_nodes_by_type(ConstantEmbedNode)
  80         old_extends_node_init(self, nodelist, *args, **kwargs)
  81
  82
  83 def render_extends_node(self, context):
  84         compiled_parent = self.get_parent(context)
  85         embeds = get_embed_dict(self.embed_list, context)
  86
  87         if BLOCK_CONTEXT_KEY not in context.render_context:
  88                 context.render_context[BLOCK_CONTEXT_KEY] = BlockContext()
  89         block_context = context.render_context[BLOCK_CONTEXT_KEY]
  90
  91         if EMBED_CONTEXT_KEY not in context.render_context:
  92                 context.render_context[EMBED_CONTEXT_KEY] = EmbedContext()
  93         embed_context = context.render_context[EMBED_CONTEXT_KEY]
  94
  95         # Add the block nodes from this node to the block context
  96         # Do the equivalent for embed nodes
  97         block_context.add_blocks(self.blocks)
  98         embed_context.add_embeds(embeds)
  99
 100         # If this block's parent doesn't have an extends node it is the root,
 101         # and its block nodes also need to be added to the block context.
 102         for node in compiled_parent.nodelist:
 103                 # The ExtendsNode has to be the first non-text node.
 104                 if not isinstance(node, TextNode):
 105                         if not isinstance(node, ExtendsNode):
 106                                 blocks = dict([(n.name, n) for n in compiled_parent.nodelist.get_nodes_by_type(BlockNode)])
 107                                 block_context.add_blocks(blocks)
 108                                 embeds = get_embed_dict(compiled_parent.nodelist.get_nodes_by_type(ConstantEmbedNode), context)
 109                                 embed_context.add_embeds(embeds)
 110                         break
 111
 112         # Explicitly render all direct embed children of this node.
 113         if self.embed_list:
 114                 for node in self.nodelist:
 115                         if isinstance(node, ConstantEmbedNode):
 116                                 node.render(context)
 117
 118         # Call Template._render explicitly so the parser context stays
 119         # the same.
 120         return compiled_parent._render(context)
 121
 122
 123 ExtendsNode.__init__ = extends_node_init
 124 ExtendsNode.render = render_extends_node
 125
 126
 127 class ConstantEmbedNode(template.Node):
 128         """Analogous to the ConstantIncludeNode, this node precompiles several variables necessary for correct rendering - namely the referenced instance or the included template."""
 129         def __init__(self, content_type, object_pk=None, template_name=None, kwargs=None):
 130                 assert template_name is not None or object_pk is not None
 131                 self.content_type = content_type
 132
 133                 kwargs = kwargs or {}
 134                 for k, v in kwargs.items():
 135                         kwargs[k] = v
 136                 self.kwargs = kwargs
 137
 138                 if object_pk is not None:
 139                         self.instance = self.compile_instance(object_pk)
 140                 else:
 141                         self.instance = None
 142
 143                 if template_name is not None:
 144                         self.template = self.compile_template(template_name[1:-1])
 145                 else:
 146                         self.template = None
 147
 148         def compile_instance(self, object_pk):
 149                 model = self.content_type.model_class()
 150                 try:
 151                         return model.objects.get(pk=object_pk)
 152                 except model.DoesNotExist:
 153                         if not hasattr(self, 'object_pk') and settings.TEMPLATE_DEBUG:
 154                                 # Then it's a constant node.
 155                                 raise
 156                         return False
 157
 158         def get_instance(self, context):
 159                 return self.instance
 160
 161         def compile_template(self, template_name):
 162                 try:
 163                         return template.loader.get_template(template_name)
 164                 except template.TemplateDoesNotExist:
 165                         if hasattr(self, 'template') and settings.TEMPLATE_DEBUG:
 166                                 # Then it's a constant node.
 167                                 raise
 168                         return False
 169
 170         def get_template(self, context):
 171                 return self.template
 172
 173         def get_content_type(self, context):
 174                 return self.content_type
 175
 176         def check_context(self, context):
 177                 if EMBED_CONTEXT_KEY not in context.render_context:
 178                         context.render_context[EMBED_CONTEXT_KEY] = EmbedContext()
 179                 embed_context = context.render_context[EMBED_CONTEXT_KEY]
 180
 181                 ct = self.get_content_type(context)
 182                 if ct not in embed_context.embeds:
 183                         embed_context.embeds[ct] = [self]
 184                 elif self not in embed_context.embeds[ct]:
 185                         embed_context.embeds[ct].append(self)
 186
 187         def mark_rendered_for(self, context):
 188                 context.render_context[EMBED_CONTEXT_KEY].rendered.append(self)
 189
 190         def render(self, context):
 191                 self.check_context(context)
 192
 193                 template = self.get_template(context)
 194                 if template is not None:
 195                         self.mark_rendered_for(context)
 196                         if template is False:
 197                                 return settings.TEMPLATE_STRING_IF_INVALID
 198                         return ''
 199
 200                 # Otherwise an instance should be available. Render the instance with the appropriate template!
 201                 instance = self.get_instance(context)
 202                 if instance is None or instance is False:
 203                         self.mark_rendered_for(context)
 204                         return settings.TEMPLATE_STRING_IF_INVALID
 205
 206                 return self.render_instance(context, instance)
 207
 208         def render_instance(self, context, instance):
 209                 try:
 210                         t = context.render_context[EMBED_CONTEXT_KEY].get_embed_template(self, context)
 211                 except (KeyError, IndexError):
 212                         self.mark_rendered_for(context)
 213                         return settings.TEMPLATE_STRING_IF_INVALID
 214
 215                 context.push()
 216                 context['embedded'] = instance
 217                 for k, v in self.kwargs.items():
 218                         context[k] = v.resolve(context)
 219                 t_rendered = t.render(context)
 220                 context.pop()
 221                 self.mark_rendered_for(context)
 222                 return t_rendered
 223
 224
 225 class EmbedNode(ConstantEmbedNode):
 226         def __init__(self, content_type, object_pk=None, template_name=None, kwargs=None):
 227                 assert template_name is not None or object_pk is not None
 228                 self.content_type = content_type
 229                 self.kwargs = kwargs or {}
 230
 231                 if object_pk is not None:
 232                         self.object_pk = object_pk
 233                 else:
 234                         self.object_pk = None
 235
 236                 if template_name is not None:
 237                         self.template_name = template_name
 238                 else:
 239                         self.template_name = None
 240
 241         def get_instance(self, context):
 242                 if self.object_pk is None:
 243                         return None
 244                 return self.compile_instance(self.object_pk.resolve(context))
 245
 246         def get_template(self, context):
 247                 if self.template_name is None:
 248                         return None
 249                 return self.compile_template(self.template_name.resolve(context))
 250
 251
 252 class InstanceEmbedNode(EmbedNode):
 253         def __init__(self, instance, kwargs=None):
 254                 self.instance = instance
 255                 self.kwargs = kwargs or {}
 256
 257         def get_template(self, context):
 258                 return None
 259
 260         def get_instance(self, context):
 261                 return self.instance.resolve(context)
 262
 263         def get_content_type(self, context):
 264                 instance = self.get_instance(context)
 265                 if not instance:
 266                         return None
 267                 return ContentType.objects.get_for_model(instance)
 268
 269
 270 def get_embedded(self):
 271         return self.template
 272
 273
 274 setattr(ConstantEmbedNode, LOADED_TEMPLATE_ATTR, property(get_embedded))
 275
 276
 277 def parse_content_type(bit, tagname):
 278         try:
 279                 app_label, model = bit.split('.')
 280         except ValueError:
 281                 raise template.TemplateSyntaxError('"%s" template tag expects the first argument to be of the form app_label.model' % tagname)
 282         try:
 283                 ct = ContentType.objects.get(app_label=app_label, model=model)
 284         except ContentType.DoesNotExist:
 285                 raise template.TemplateSyntaxError('"%s" template tag requires an argument of the form app_label.model which refers to an installed content type (see django.contrib.contenttypes)' % tagname)
 286         return ct
 287
 288
 289 def do_embed(parser, token):
 290         """
 291         The {% embed %} tag can be used in two ways:
 292         {% embed <app_label>.<model_name> with <template> %} :: Sets which template will be used to render a particular model.
 293         {% embed (<app_label>.<model_name> <object_pk> || <instance>) [<argname>=<value> ...] %} :: Embeds the instance specified by the given parameters in the document with the previously-specified template. Any kwargs provided will be passed into the context of the template.
 294         """
 295         bits = token.split_contents()
 296         tag = bits.pop(0)
 297
 298         if len(bits) < 1:
 299                 raise template.TemplateSyntaxError('"%s" template tag must have at least two arguments.' % tag)
 300
 301         if len(bits) == 3 and bits[-2] == 'with':
 302                 ct = parse_content_type(bits[0], tag)
 303
 304                 if bits[2][0] in ['"', "'"] and bits[2][0] == bits[2][-1]:
 305                         return ConstantEmbedNode(ct, template_name=bits[2])
 306                 return EmbedNode(ct, template_name=bits[2])
 307
 308         # Otherwise they're trying to embed a certain instance.
 309         kwargs = {}
 310         try:
 311                 bit = bits.pop()
 312                 while '=' in bit:
 313                         k, v = bit.split('=')
 314                         kwargs[k] = parser.compile_filter(v)
 315                         bit = bits.pop()
 316                 bits.append(bit)
 317         except IndexError:
 318                 raise template.TemplateSyntaxError('"%s" template tag expects at least one non-keyword argument when embedding instances.')
 319
 320         if len(bits) == 1:
 321                 instance = parser.compile_filter(bits[0])
 322                 return InstanceEmbedNode(instance, kwargs)
 323         elif len(bits) > 2:
 324                 raise template.TemplateSyntaxError('"%s" template tag expects at most 2 non-keyword arguments when embedding instances.')
 325         ct = parse_content_type(bits[0], tag)
 326         pk = bits[1]
 327
 328         try:
 329                 int(pk)
 330         except ValueError:
 331                 return EmbedNode(ct, object_pk=parser.compile_filter(pk), kwargs=kwargs)
 332         else:
 333                 return ConstantEmbedNode(ct, object_pk=pk, kwargs=kwargs)
 334
 335
 336 register.tag('embed', do_embed)