cloud-init

jinja-template doesn't support 'do' extension.

Bug #1962759 reported by paul bruno on 2022-03-02

This bug affects 1 person

Affects		Status	Importance	Assigned to	Milestone
	cloud-init	Fix Released	Medium	paul bruno

Bug Description

example user-data file with jinja

## template: jinja
#!/bin/sh

{% set data_result = [] %}
{% set data_input = [1,2,3] %}
{% for i in data_input %}
{% do data_result.append(i) %}
{% endfor %}
echo results: {{data_result}} >>results.out

The following exception is thrown when using jinja2 'do' statement.

jinja2.exceptions.TemplateSyntaxError: Encountered unknown tag 'do'. Jinja was looking for the following tags: 'endfor' or 'else'. The innermost block that needs to be closed is 'for'.

I'm using cloud-init from a 64bitencoded file passed into terraform azure provider custom_data.

Revision history for this message

paul bruno (thetoolsmith) wrote on 2022-03-02:

cloud-init logs Edit (219.7 KiB, application/x-tar)

Revision history for this message

Chad Smith (chad.smith) wrote on 2022-03-03:

Thank you for filing this bug and making Ubuntu and cloud-init better.

In investigation on this issue, I can see we don't load the jinja extension `ExprStmtExtension` or "do" extension.
In testing yesterday, I think we can just provide extensions=["jinja2.ext.do"] to our JTemplate in cloudinit.templater.

For versions of cloud-init that don't yet have a fix for this, the workaround in the absence of the "do" extension, they can use jinja default filter to return an empty string instead of printing None.

{% set data_result = [] %}
{% set data_input = [1,2,3] %}
{% for i in data_input %}
{{ data_result.append(i)|default("",True) }}
{% endfor %}
{{data_result}}

Changed in cloud-init:
status:	New → Triaged
status:	Triaged → In Progress
importance:	Undecided → Medium
assignee:	nobody → paul bruno (thetoolsmith)

Revision history for this message

Chad Smith (chad.smith) wrote on 2022-03-03:

Upstream PR accepted which will resolve this bug in cloud-init
https://github.com/canonical/cloud-init/pull/1314

Thank you Paul.

Revision history for this message

Chad Smith (chad.smith) wrote on 2022-03-03:

Upstream commit landed which addresses this issue.
https://github.com/canonical/cloud-init/commit/21973bdf7414cc2ebd2b0b2303c0d09400fd0022

Changed in cloud-init:
status:	In Progress → Fix Committed

Revision history for this message

Brett Holman (holmanb) wrote on 2022-05-18: Fixed in cloud-init version 22.2.

This bug is believed to be fixed in cloud-init in version 22.2. If this is still a problem for you, please make a comment and set the state back to New

Thank you.