python - 将列表参数传递给 Jinja2 扩展中的调用节点

Question

几个小时以来，我一直在努力创建 Jinja2 扩展，看来我肯定被困在一个特定的点上:将列表参数传递给 Call 节点。我试图从其他一些工作扩展中获得灵感，但我不明白为什么我的东西不能工作而我的引用代码可以工作。

基本上我想要的是在我的模板中有这样的东西:

{% usebundle "common", "treeview"%}

这应该将“common”和“treeview”字符串添加到上下文中的某个列表中。

以下是我的代码的关键部分:

class MyExtension(Extension):
  def __init__(self, environment):
    super(MyExtension, self).__init__(environment)

  def parse(self, parser):
    lineno = parser.stream.next().lineno
    names = []
    while parser.stream.current.type != 'block_end':
      names.append(parser.parse_expression())
      parser.stream.skip_if('comma')

    # At this point, names is a correctly filled array of names
    call = self.call_method('_callback', args=[nodes.List(names)])
    result = nodes.CallBlock([call], [], [], [])
    result.set_lineno(lineno)
    return result

  def _callback(self, names, caller=None):
    # Here names should contain a list of names, but it's either undefined or 
    # a list of Undefined, or I get an error before reaching this callback
    # (generally saying that arguments cannot be read)
    pass

我尝试了几件事，但让我说问题确实出在参数格式(解析函数中 names 值的内容)的是，如果我替换 nodes.List(names) 通过 nodes.Const(42)，我在回调参数中收到正确的 42 值。

[编辑] 此版本代码的错误详细信息如下:

Exception on /login [GET]
Traceback (most recent call last):
  File "E:\Python27\lib\site-packages\flask-0.9-py2.7.egg\flask\app.py", line 1687, in wsgi_app
    response = self.full_dispatch_request()
  File "E:\Python27\lib\site-packages\flask-0.9-py2.7.egg\flask\app.py", line 1360, in full_dispatch_request
    rv = self.handle_user_exception(e)
  File "E:\Python27\lib\site-packages\flask-0.9-py2.7.egg\flask\app.py", line 1358, in full_dispatch_request
    rv = self.dispatch_request()
  File "E:\Python27\lib\site-packages\flask-0.9-py2.7.egg\flask\app.py", line 1344, in dispatch_request
    return self.view_functions[rule.endpoint](**req.view_args)
  File "E:\myapplication\user.py", line 126, in login
    return template_or_json('user/login.html', form=form)
  File "E:\myapplication\ajax.py", line 32, in template_or_json
    return render_template(template_name, **context)
  File "E:\Python27\lib\site-packages\flask-0.9-py2.7.egg\flask\templating.py", line 125, in render_template
    context, ctx.app)
  File "E:\Python27\lib\site-packages\flask-0.9-py2.7.egg\flask\templating.py", line 107, in _render
    rv = template.render(context)
  File "E:\Python27\lib\site-packages\jinja2-2.6-py2.7.egg\jinja2\environment.py", line 894, in render
    return self.environment.handle_exception(exc_info, True)
  File "E:\myapplication\templates\user\login.html", line 1, in top-level template code
    {% extends "layout.html" %}
  File "E:\Python27\lib\site-packages\jinja2-2.6-py2.7.egg\jinja2\environment.py", line 443, in _generate
    return generate(source, self, name, filename, defer_init=defer_init)
  File "E:\Python27\lib\site-packages\jinja2-2.6-py2.7.egg\jinja2\compiler.py", line 63, in generate
    generator.visit(node)
  File "E:\Python27\lib\site-packages\jinja2-2.6-py2.7.egg\jinja2\visitor.py", line 38, in visit
    return f(node, *args, **kwargs)
  File "E:\Python27\lib\site-packages\jinja2-2.6-py2.7.egg\jinja2\compiler.py", line 803, in visit_Template
    frame.inspect(node.body)
  File "E:\Python27\lib\site-packages\jinja2-2.6-py2.7.egg\jinja2\compiler.py", line 201, in inspect
    visitor.visit(node)
  File "E:\Python27\lib\site-packages\jinja2-2.6-py2.7.egg\jinja2\visitor.py", line 38, in visit
    return f(node, *args, **kwargs)
  File "E:\Python27\lib\site-packages\jinja2-2.6-py2.7.egg\jinja2\compiler.py", line 347, in visit_CallBlock
    self.visit(node.call)
  File "E:\Python27\lib\site-packages\jinja2-2.6-py2.7.egg\jinja2\visitor.py", line 39, in visit
    return self.generic_visit(node, *args, **kwargs)
  File "E:\Python27\lib\site-packages\jinja2-2.6-py2.7.egg\jinja2\visitor.py", line 43, in generic_visit
    for node in node.iter_child_nodes():
AttributeError: 'list' object has no attribute 'iter_child_nodes'

Answer 1

CallBlock 期望实际调用作为第一个参数，而不是一些调用列表。

所以，你只需要使用

nodes.CallBlock(call, [], [], [])

代替

nodes.CallBlock([call], [], [], [])