placeholder.py 文件源码

def _scan_placeholders(nodelist, current_block=None, ignore_blocks=None):
    from cms.templatetags.cms_tags import Placeholder

    placeholders = []
    if ignore_blocks is None:
        # List of BlockNode instances to ignore.
        # This is important to avoid processing overriden block nodes.
        ignore_blocks = []

    for node in nodelist:
        # check if this is a placeholder first
        if isinstance(node, Placeholder):
            placeholders.append(node.get_name())
        elif isinstance(node, IncludeNode):
            # if there's an error in the to-be-included template, node.template becomes None
            if node.template:
                # Check if it quacks like a template object, if not
                # presume is a template path and get the object out of it
                if not callable(getattr(node.template, 'render', None)):
                    # If it's a variable there is no way to expand it at this stage so we
                    # need to skip it
                    if isinstance(node.template.var, Variable):
                        continue
                    else:
                        template = get_template(node.template.var)
                else:
                    template = node.template
                placeholders += _scan_placeholders(_get_nodelist(template), current_block)
        # handle {% extends ... %} tags
        elif isinstance(node, ExtendsNode):
            placeholders += _extend_nodelist(node)
        # in block nodes we have to scan for super blocks
        elif isinstance(node, VariableNode) and current_block:
            if node.filter_expression.token == 'block.super':
                if not hasattr(current_block.super, 'nodelist'):
                    raise TemplateSyntaxError("Cannot render block.super for blocks without a parent.")
                placeholders += _scan_placeholders(_get_nodelist(current_block.super), current_block.super)
        # ignore nested blocks which are already handled
        elif isinstance(node, BlockNode) and node.name in ignore_blocks:
            continue
        # if the node has the newly introduced 'child_nodelists' attribute, scan
        # those attributes for nodelists and recurse them
        elif hasattr(node, 'child_nodelists'):
            for nodelist_name in node.child_nodelists:
                if hasattr(node, nodelist_name):
                    subnodelist = getattr(node, nodelist_name)
                    if isinstance(subnodelist, NodeList):
                        if isinstance(node, BlockNode):
                            current_block = node
                        placeholders += _scan_placeholders(subnodelist, current_block, ignore_blocks)
        # else just scan the node for nodelist instance attributes
        else:
            for attr in dir(node):
                obj = getattr(node, attr)
                if isinstance(obj, NodeList):
                    if isinstance(node, BlockNode):
                        current_block = node
                    placeholders += _scan_placeholders(obj, current_block, ignore_blocks)
    return placeholders