Conditionally add data-attributes in Jekyll - if-statement

Question

My basic YAML Front Matter for blog posts looks as:
layout: post
title: 'Crepes'
permalink: /crepes/
src: '/assets/images/crepes.jpg'
date: 2018-05-24 21:41:00
origin: http//...
ingredients:
- ingredient1: amount
- ingredient2: amount
Here is my index.html to display entries:
<ul>
{% for post in site.posts %}
<li data-title='{{ post.title }}' data-origin="{{ post.origin }}"
data-src="{{ post.src | prepend: relative_url}}"
data-content='{ "ingredients": {{ post.ingredients | jsonify }} }'>
<a href="{{ site.baseurl }}{{ post.url }}">
<img src="{{ post.src | prepend: relative_url }}" alt={{ post.title }}/>
</a>
</li>
{% endfor %}
</ul>
The problem is:
Some posts are supposed to have no origin value, like origin:. And I am looking for a way to add data-origin attribute only if it's value specified in YAML Front Matter.
Liquid give following option:
{% if condition %}
<li>....</li>
{% endif %}
Is there any way to use it inside of html tag? In my case I expect something like this:
{% for post in site.posts %}
<li
{% if post.origin has value %}
data-origin="{{ post.origin }}"
{% endif %}">
</li>
{% endfor %}

Answer 1

Here I see four cases :
post.origin is not present in front matter :
post.origin == null
post.origin is present in front matter, but not set (post.origin:)
=> post.origin == null`
post.origin is present in front matter, but set to empty string (post.origin: "")
=> post.origin == ""
post.origin is present in front matter, and set to valid string (post.origin: "toto")
=> post.origin == "toto"
Results are conform to Truthy and falsy Liquid documentation.
From there, using logical liquid operators, we can build a condition like :
<li
{% if post.origin and post.origin != "" %}
data-origin="{{ post.origin }}"{% endif %}>
</li>
Note that post.origin means post.origin != null.