[BUG][Jinja2][value-assign] Can't assign value in a loop?

[Simon Jones]

Hi all,

I'm using Jinja2 template to generate config files, but I found a BUG, which is I could not assign value in a loop, like this:

1) use this template, could generate 'uuusevrf'

{% block vrf_mgmt_interface %}
{% set usevrf = 'no' %}
{% set usevrf = 'nono' %}
{% if MGMT_INTERFACE %}
{% set uuusevrf = 'yes' %}
{%   for (name, prefix) in MGMT_INTERFACE %}
{%     if name == 'eth0' %}
{%       if MGMT_INTERFACE[(name, prefix)].has_key('vrfname') %}
{%         if prefix | ipv4 %}
USE_VRF=2
IP_VERSION=4
ETH_NAME=eth0
ETH_IP={{ prefix | ip }}
ETH_SUB_NET={{ prefix | network }}/{{ prefix | prefixlen }}
ETH_LOOKUP_IP={{ prefix | ip }}
VRFNAME={{ MGMT_INTERFACE[(name, prefix)]['vrfname'] }}
GWADDR={{ MGMT_INTERFACE[(name, prefix)]['gwaddr'] }}
{%         else %}
USE_VRF=2
IP_VERSION=6
ETH_NAME=eth0
ETH_IP={{ prefix | ip }}
ETH_SUB_NET={{ prefix | network }}/{{ prefix | prefixlen }}
ETH_LOOKUP_IP={{ prefix | ip }}
VRFNAME={{ MGMT_INTERFACE[(name, prefix)]['vrfname'] }}
GWADDR={{ MGMT_INTERFACE[(name, prefix)]['gwaddr'] }}
{%         endif %}
{%       else %}
USE_VRF=1
{%       endif %}
{%     endif %}
{%   endfor %}
{% endif %}
{{ usevrf }}
{{ uuusevrf }}
{% endblock vrf_mgmt_interface %}

2) could generate 'uuusevrf', this is result:

rfaces.j211:~# sonic-cfggen -d -t /usr/share/sonic/templates/vrf_management_inter
USE_VRF=2
IP_VERSION=4
ETH_NAME=eth0
ETH_IP=172.18.8.211
ETH_SUB_NET=172.18.8.0/24
ETH_LOOKUP_IP=172.18.8.211
VRFNAME=mgmtvrf
GWADDR=172.18.8.1
nono
yes

2) use this template, could NOT generate 'uuusevrf'

{% block vrf_mgmt_interface %}
{% set usevrf = 'no' %}
{% set usevrf = 'nono' %}
{% if MGMT_INTERFACE %}
{%   for (name, prefix) in MGMT_INTERFACE %}
{% set uuusevrf = 'yes' %}
{%     if name == 'eth0' %}
{%       if MGMT_INTERFACE[(name, prefix)].has_key('vrfname') %}
{%         if prefix | ipv4 %}
USE_VRF=2
IP_VERSION=4
ETH_NAME=eth0
ETH_IP={{ prefix | ip }}
ETH_SUB_NET={{ prefix | network }}/{{ prefix | prefixlen }}
ETH_LOOKUP_IP={{ prefix | ip }}
VRFNAME={{ MGMT_INTERFACE[(name, prefix)]['vrfname'] }}
GWADDR={{ MGMT_INTERFACE[(name, prefix)]['gwaddr'] }}
{%         else %}
USE_VRF=2
IP_VERSION=6
ETH_NAME=eth0
ETH_IP={{ prefix | ip }}
ETH_SUB_NET={{ prefix | network }}/{{ prefix | prefixlen }}
ETH_LOOKUP_IP={{ prefix | ip }}
VRFNAME={{ MGMT_INTERFACE[(name, prefix)]['vrfname'] }}
GWADDR={{ MGMT_INTERFACE[(name, prefix)]['gwaddr'] }}
{%         endif %}
{%       else %}
USE_VRF=1
{%       endif %}
{%     endif %}
{%   endfor %}
{% endif %}
{{ usevrf }}
{{ uuusevrf }}
{% endblock vrf_mgmt_interface %}

4) could NOT generate, this is result:

rfaces.j211:~# sonic-cfggen -d -t /usr/share/sonic/templates/vrf_management_inter
USE_VRF=2
IP_VERSION=4
ETH_NAME=eth0
ETH_IP=172.18.8.211
ETH_SUB_NET=172.18.8.0/24
ETH_LOOKUP_IP=172.18.8.211
VRFNAME=mgmtvrf
GWADDR=172.18.8.1
nono

So, why ???

You could see that, same data, just the position of this line ({% set uuusevrf = 'yes' %}) is different. And the result show it definitely go into loop, but why this line NOT work ??? 

BTW, It's hard to debug !!!!!!

[Simon Jones]

And why do not support 'break' ......

在 2019年1月3日星期四 UTC+8下午4:30:34，Simon Jones写道：

[Juan Pablo Scaletti]

As you can read on the documentation, no, you can't assign a value in a
loop and use it outside the loop, unless you use a namespace:

http://jinja.pocoo.org/docs/2.10/templates/#assignments (see: Scoping
Behavior)

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Juan Pablo Scaletti

[Simon Jones]

Cool, but if this is a bug?

在 2019年1月3日星期四 UTC+8下午11:12:45，Juan Pablo Scaletti写道：