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

[ubuntu-server-builder]

This bug was originally filed in Launchpad as LP: #1962759

Launchpad details

affected_projects = []
assignee = thetoolsmith
assignee_name = paul bruno
date_closed = 2022-05-18T16:51:42.036870+00:00
date_created = 2022-03-02T15:48:24.887425+00:00
date_fix_committed = 2022-03-03T20:51:14.058089+00:00
date_fix_released = 2022-05-18T16:51:42.036870+00:00
id = 1962759
importance = medium
is_complete = True
lp_url = https://bugs.launchpad.net/cloud-init/+bug/1962759
milestone = None
owner = thetoolsmith
owner_name = paul bruno
private = False
status = fix_released
submitter = thetoolsmith
submitter_name = paul bruno
tags = []
duplicates = []

Launchpad user paul bruno(thetoolsmith) wrote on 2022-03-02T15:48:24.887425+00:00

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.

[ubuntu-server-builder]

Launchpad user paul bruno(thetoolsmith) wrote on 2022-03-02T15:48:24.887425+00:00

Launchpad attachments: cloud-init logs

[ubuntu-server-builder]

Launchpad user Chad Smith(chad.smith) wrote on 2022-03-03T03:40:08.733482+00:00

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}}

[ubuntu-server-builder]

Launchpad user Chad Smith(chad.smith) wrote on 2022-03-03T03:41:34.417444+00:00

Upstream PR accepted which will resolve this bug in cloud-init
#1314

Thank you Paul.

[ubuntu-server-builder]

Launchpad user Chad Smith(chad.smith) wrote on 2022-03-03T20:51:08.815353+00:00

Upstream commit landed which addresses this issue.
21973bd

[ubuntu-server-builder]

Launchpad user Brett Holman(holmanb) wrote on 2022-05-18T16:51:42.811997+00:00

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.