Experimental {% linemode %} and {% line %} template tags

linemode.py

class LineModeNode(Node):
    def __init__(self, nodelist):
        self.nodelist = nodelist

    def render(self, context):
        context["__lines__"] = []
        self.nodelist.render(context)
        return "\n".join(context["__lines__"])


@register.tag
def linemode(parser, token):
    """ Trim whitespace and newlines outside {% line %} blocks.

    Example usage::

        {% linemode %}
            {% line %}Line one.{% endline %}
            This content will be ignored.
            {% if True %}
                {% line %}Line two.{% endline %}
            {% endif %}
        {% endlinemode %}

    This example returns this text::

        Line one.
        Line two.

    """
    nodelist = parser.parse(("endlinemode",))
    parser.delete_first_token()
    return LineModeNode(nodelist)


class LineNode(Node):
    def __init__(self, nodelist):
        self.nodelist = nodelist

    def render(self, context):
        context["__lines__"].append(self.nodelist.render(context))
        return ""


@register.tag
def line(parser, token):
    """ For use with {% linemode %}.

    Renders the enclosed content and appends it to context["__lines__"],
    instead of returning it.

    """

    nodelist = parser.parse(("endline",))
    parser.delete_first_token()
    return LineNode(nodelist)