Extra newline at end of output

[omolenkamp]

Even with trim_blocks=True and lstrip_blocks=True, a template like this will result in not one, but two newlines at the end of the generated output:

{% for line in lines %}
{{ line }}
{% endfor %}

With lines = ['a', 'b', 'c'], this will generate:

a\n
b\n
c\n
\n

I'd expect the output to end with a single newline instead of two.

If there is content after {% endfor %}, no additional newline will be generated, so this template:

{% for line in lines %}
{{ line }}
{% endfor %}
x

will generate this output, which is what I'd expect:

a\n
b\n
c\n
x\n

Environment:

• Python version: 3.12.11
• Jinja version: 3.1.6

[davidism]

https://jinja.palletsprojects.com/en/stable/templates/#whitespace-control

You need to use whitespace control marks on the tags as well. There is a newline between the content and end tag.

[omolenkamp]

Are you suggesting to use {%- endfor %}? That will give a single line abc, instead of three lines of output.

[omolenkamp]

Also, as demonstrated by the second template, the whitespace before {% endfor %} doesn't seem to be the problem, as it will correctly output a single newline when there is trailing content.

[omolenkamp]

I think that what is happening is that Salt (which is what I'm using Jinja in) is adding a final newline because keep_trailing_newline didn't exist at the time, saltstack/salt#2773.

Their fix works as intended when a template ends with content, but not when the last line is a Jinja block.

I'll open an issue with Salt to remove the fix and use keep_trailing_newline=true instead.