Filters were in "assign" but not in for loops?

[larsks]

I have a filter post_is_future that looks like this:

	eleventyConfig.addFilter("post_is_future", (posts) => {
		const now = new Date();
		return posts.filter((post) => post.date > now);
	});

When I attempt to use it like this:

{% for post in collections.post | post_is_future | sort: 'date' %}
- **{{ post.data.title }}** - {{ post.date | date: "%Y-%m-%d" }}
{% endfor %}

It doesn't work -- eleventy acts like the filter isn't there. But if I write it like this:

{% assign future_posts = collections.post | post_is_future | sort: 'date' %}
{% for post in future_posts %}
- **{{ post.data.title }}** - {{ post.date | date: "%Y-%m-%d" }}
{% endfor %}

It works just fine.

What's going on here?

[dwkns]

In your first example the for post in collections.post sets up the loop it doesn't return a value. So you are effectively not passing anything to the filter.

In your second example you are specifically setting a variable to collections.post and therefore that value is passed to the filter.

For some reason Liquid doesn't produce an error, but if you try the same in Nunjucks it does.

If your goal is to simplify your template, you could create a custom collection which returns a sorted list of future posts.