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 not in embeds:
  69                         embeds[ct] = [e]
  70                 else:
  71                         embeds[ct].append(e)
  72         return embeds
  73
  74
  75 def extends_node_init(self, nodelist, *args, **kwargs):
  76         self.embed_list = nodelist.get_nodes_by_type(ConstantEmbedNode)
  77         old_extends_node_init(self, nodelist, *args, **kwargs)
  78
  79
  80 def render_extends_node(self, context):
  81         compiled_parent = self.get_parent(context)
  82         embeds = get_embed_dict(self.embed_list, context)
  83
  84         if BLOCK_CONTEXT_KEY not in context.render_context:
  85                 context.render_context[BLOCK_CONTEXT_KEY] = BlockContext()
  86         block_context = context.render_context[BLOCK_CONTEXT_KEY]
  87
  88         if EMBED_CONTEXT_KEY not in context.render_context:
  89                 context.render_context[EMBED_CONTEXT_KEY] = EmbedContext()
  90         embed_context = context.render_context[EMBED_CONTEXT_KEY]
  91
  92         # Add the block nodes from this node to the block context
  93         # Do the equivalent for embed nodes
  94         block_context.add_blocks(self.blocks)
  95         embed_context.add_embeds(embeds)
  96
  97         # If this block's parent doesn't have an extends node it is the root,
  98         # and its block nodes also need to be added to the block context.
  99         for node in compiled_parent.nodelist:
 100                 # The ExtendsNode has to be the first non-text node.
 101                 if not isinstance(node, TextNode):
 102                         if not isinstance(node, ExtendsNode):
 103                                 blocks = dict([(n.name, n) for n in compiled_parent.nodelist.get_nodes_by_type(BlockNode)])
 104                                 block_context.add_blocks(blocks)
 105                                 embeds = get_embed_dict(compiled_parent.nodelist.get_nodes_by_type(ConstantEmbedNode), context)
 106                                 embed_context.add_embeds(embeds)
 107                         break
 108
 109         # Explicitly render all direct embed children of this node.
 110         if self.embed_list:
 111                 for node in self.nodelist:
 112                         if isinstance(node, ConstantEmbedNode):
 113                                 node.render(context)
 114
 115         # Call Template._render explicitly so the parser context stays
 116         # the same.
 117         return compiled_parent._render(context)
 118
 119
 120 ExtendsNode.__init__ = extends_node_init
 121 ExtendsNode.render = render_extends_node
 122
 123
 124 class ConstantEmbedNode(template.Node):
 125         """Analogous to the ConstantIncludeNode, this node precompiles several variables necessary for correct rendering - namely the referenced instance or the included template."""
 126         def __init__(self, content_type, object_pk=None, template_name=None, kwargs=None):
 127                 assert template_name is not None or object_pk is not None
 128                 self.content_type = content_type
 129
 130                 kwargs = kwargs or {}
 131                 for k, v in kwargs.items():
 132                         kwargs[k] = v
 133                 self.kwargs = kwargs
 134
 135                 if object_pk is not None:
 136                         self.instance = self.compile_instance(object_pk)
 137                 else:
 138                         self.instance = None
 139
 140                 if template_name is not None:
 141                         self.template = self.compile_template(template_name[1:-1])
 142                 else:
 143                         self.template = None
 144
 145         def compile_instance(self, object_pk):
 146                 self.object_pk = object_pk
 147                 model = self.content_type.model_class()
 148                 try:
 149                         return model.objects.get(pk=object_pk)
 150                 except model.DoesNotExist:
 151                         if not hasattr(self, 'object_pk') and settings.TEMPLATE_DEBUG:
 152                                 # Then it's a constant node.
 153                                 raise
 154                         return False
 155
 156         def get_instance(self, context):
 157                 return self.instance
 158
 159         def compile_template(self, template_name):
 160                 try:
 161                         return template.loader.get_template(template_name)
 162                 except template.TemplateDoesNotExist:
 163                         if hasattr(self, 'template') and settings.TEMPLATE_DEBUG:
 164                                 # Then it's a constant node.
 165                                 raise
 166                         return False
 167
 168         def get_template(self, context):
 169                 return self.template
 170
 171         def get_content_type(self, context):
 172                 return self.content_type
 173
 174         def check_context(self, context):
 175                 if EMBED_CONTEXT_KEY not in context.render_context:
 176                         context.render_context[EMBED_CONTEXT_KEY] = EmbedContext()
 177                 embed_context = context.render_context[EMBED_CONTEXT_KEY]
 178
 179                 ct = self.get_content_type(context)
 180                 if ct not in embed_context.embeds:
 181                         embed_context.embeds[ct] = [self]
 182                 elif self not in embed_context.embeds[ct]:
 183                         embed_context.embeds[ct].append(self)
 184
 185         def mark_rendered_for(self, context):
 186                 context.render_context[EMBED_CONTEXT_KEY].rendered.append(self)
 187
 188         def render(self, context):
 189                 self.check_context(context)
 190
 191                 template = self.get_template(context)
 192                 if template is not None:
 193                         self.mark_rendered_for(context)
 194                         if template is False:
 195                                 return settings.TEMPLATE_STRING_IF_INVALID
 196                         return ''
 197
 198                 # Otherwise an instance should be available. Render the instance with the appropriate template!
 199                 instance = self.get_instance(context)
 200                 if instance is None or instance is False:
 201                         self.mark_rendered_for(context)
 202                         return settings.TEMPLATE_STRING_IF_INVALID
 203
 204                 return self.render_instance(context, instance)
 205
 206         def render_instance(self, context, instance):
 207                 try:
 208                         t = context.render_context[EMBED_CONTEXT_KEY].get_embed_template(self, context)
 209                 except (KeyError, IndexError):
 210                         if settings.TEMPLATE_DEBUG:
 211                                 raise
 212                         self.mark_rendered_for(context)
 213                         return settings.TEMPLATE_STRING_IF_INVALID
 214
 215                 context.push()
 216                 context['embedded'] = instance
 217                 kwargs = {}
 218                 for k, v in self.kwargs.items():
 219                         kwargs[k] = v.resolve(context)
 220                 context.update(kwargs)
 221                 t_rendered = t.render(context)
 222                 context.pop()
 223                 self.mark_rendered_for(context)
 224                 return t_rendered
 225
 226
 227 class EmbedNode(ConstantEmbedNode):
 228         def __init__(self, content_type, object_pk=None, template_name=None, kwargs=None):
 229                 assert template_name is not None or object_pk is not None
 230                 self.content_type = content_type
 231                 self.kwargs = kwargs or {}
 232
 233                 if object_pk is not None:
 234                         self.object_pk = object_pk
 235                 else:
 236                         self.object_pk = None
 237
 238                 if template_name is not None:
 239                         self.template_name = template_name
 240                 else:
 241                         self.template_name = None
 242
 243         def get_instance(self, context):
 244                 if self.object_pk is None:
 245                         return None
 246                 return self.compile_instance(self.object_pk.resolve(context))
 247
 248         def get_template(self, context):
 249                 if self.template_name is None:
 250                         return None
 251                 return self.compile_template(self.template_name.resolve(context))
 252
 253
 254 class InstanceEmbedNode(EmbedNode):
 255         def __init__(self, instance, kwargs=None):
 256                 self.instance = instance
 257                 self.kwargs = kwargs or {}
 258
 259         def get_template(self, context):
 260                 return None
 261
 262         def get_instance(self, context):
 263                 return self.instance.resolve(context)
 264
 265         def get_content_type(self, context):
 266                 return ContentType.objects.get_for_model(self.get_instance(context))
 267
 268
 269 def get_embedded(self):
 270         return self.template
 271
 272
 273 setattr(ConstantEmbedNode, LOADED_TEMPLATE_ATTR, property(get_embedded))
 274
 275
 276 def get_content_type(bit):
 277         try:
 278                 app_label, model = bit.split('.')
 279         except ValueError:
 280                 raise template.TemplateSyntaxError('"%s" template tag expects the first argument to be of the form app_label.model' % tag)
 281         try:
 282                 ct = ContentType.objects.get(app_label=app_label, model=model)
 283         except ContentType.DoesNotExist:
 284                 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)' % tag)
 285         return ct
 286
 287
 288 def do_embed(parser, token):
 289         """
 290         The {% embed %} tag can be used in two ways:
 291         {% embed <app_label>.<model_name> with <template> %} :: Sets which template will be used to render a particular model.
 292         {% 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.
 293         """
 294         bits = token.split_contents()
 295         tag = bits.pop(0)
 296
 297         if len(bits) < 1:
 298                 raise template.TemplateSyntaxError('"%s" template tag must have at least two arguments.' % tag)
 299
 300         if len(bits) == 3 and bits[-2] == 'with':
 301                 ct = get_content_type(bits[0])
 302
 303                 if bits[2][0] in ['"', "'"] and bits[2][0] == bits[2][-1]:
 304                         return ConstantEmbedNode(ct, template_name=bits[2])
 305                 return EmbedNode(ct, template_name=bits[2])
 306
 307         # Otherwise they're trying to embed a certain instance.
 308         kwargs = {}
 309         try:
 310                 bit = bits.pop()
 311                 while '=' in bit:
 312                         k, v = bit.split('=')
 313                         kwargs[k] = parser.compile_filter(v)
 314                         bit = bits.pop()
 315                 bits.append(bit)
 316         except IndexError:
 317                 raise template.TemplateSyntaxError('"%s" template tag expects at least one non-keyword argument when embedding instances.')
 318
 319         if len(bits) == 1:
 320                 instance = parser.compile_filter(bits[0])
 321                 return InstanceEmbedNode(instance, kwargs)
 322         elif len(bits) > 2:
 323                 raise template.TemplateSyntaxError('"%s" template tag expects at most 2 non-keyword arguments when embedding instances.')
 324         ct = get_content_type(bits[0])
 325         pk = bits[1]
 326
 327         try:
 328                 int(pk)
 329         except ValueError:
 330                 return EmbedNode(ct, object_pk=parser.compile_filter(pk), kwargs=kwargs)
 331         else:
 332                 return ConstantEmbedNode(ct, object_pk=pk, kwargs=kwargs)
 333
 334
 335 register.tag('embed', do_embed)