- added with-statement extension.

.. _with-extension:

With Statement

--------------

**Import name:** `jinja2.ext.with_`

.. versionadded:: 2.3

This extension adds support for the with keyword.  Using this keyword it

is possible to enforce a nested scope in a template.  Variables can be

declared directly in the opening block of the with statement or using a

standard `set` statement directly within.

With Statement

~~~~~~~~~~~~~~

.. versionadded:: 2.3

If the application enables the :ref:`with-extension` it is possible to

use the `with` keyword in templates.  This makes it possible to create

a new inner scope.  Variables set within this scope are not visible

outside of the scope.

With in a nutshell::

    {% with %}

        {% set foo = 42 %}

        {{ foo }}           foo is 42 here

    {% endwith %}

    foo is not visible here any longer

Because it is common to set variables at the beginning of the scope

you can do that within the with statement.  The following two examples

are equivalent::

    {% with foo = 42 %}

        {{ foo }}

    {% endwith %}

    {% with %}

        {% set foo = 42 %}

        {{ foo }}

    {% endwith %}

class WithExtension(Extension):

    """Adds support for a django-like with block."""

    tags = set(['with'])

    def parse(self, parser):

        node = nodes.Scope(lineno=next(parser.stream).lineno)

        assignments = []

        while parser.stream.current.type != 'block_end':

            lineno = parser.stream.current.lineno

            if assignments:

                parser.stream.expect('comma')

            target = parser.parse_assign_target()

            parser.stream.expect('assign')

            expr = parser.parse_expression()

            assignments.append(nodes.Assign(target, expr, lineno=lineno))

        node.body = assignments + \

            list(parser.parse_statements(('name:endwith',),

                                         drop_needle=True))

        return node

with_ = WithExtension

def test_with():

    env = Environment(extensions=['jinja2.ext.with_'])

    tmpl = env.from_string('''\

    {% with a=42, b=23 -%}

        {{ a }} = {{ b }}

    {% endwith -%}

        {{ a }} = {{ b }}\

    ''')

    assert [x.strip() for x in tmpl.render(a=1, b=2).splitlines()] \

        == ['42 = 23', '1 = 2']