variables in include tag with liquid filters

[jens-na]

Use variable {% include %} with filters
This pull request adds support for filters when using the include tag with a variable.
To be more precise:

Since PR #1495 it is possible to use variables inside an include tag, like that:

    {% for item in page.dependencies %}
        {% include {{item}} %}
    {% endfor %}

but unfortunately you cannot use filters.

With this pull reuqest you can use something like this:

    {% for item in page.dependencies %}
        {% include {{ item | append: '.html' }} %}
    {% endfor %}

This is especially useful when you want to modify the file/filename which should get included.

Possible use cases

Append .html to the file name

{% include {{ item | append: '.html' }} %}

Make sure the file name is lowercase

{% include {{ item | downcase | append: '.html' }} %}

Prepend a directory to choose another directory inside the _includes/ directory

{% include {{ item | downcase | prepend: '/dependencies/' | append: '.html' }} %}
==> ./_includes/dependencies/<item>.html

[coveralls]

Coverage remained the same when pulling 43ef9a2 on jens-na:include-variable-liquid-filters into 12a55b8 on jekyll:master.

[parkr]

/cc @maul-esel

[maul-esel]

If you want to use file to output the real path and not the variable etc. (in case it is one), that's ok. But as file already contains the full path in this method, you might wanna remove the #{INCLUDES_DIR} part in this message and the one above 😉

[maul-esel]

Looks great! Just the one comment above.

[maul-esel]

Oh and also, as we discussed in #1789, this fixes cases like {% include {{ var }} %} (spaces inside brackets), so you might wanna remove the note concerning this from the docs (here or in a separate PR / commit once this is merged).

[coveralls]

Coverage increased (+0.42%) when pulling 412fe8b on jens-na:include-variable-liquid-filters into 12a55b8 on jekyll:master.

[maul-esel]

👍

[coveralls]

Coverage increased (+0.24%) when pulling 412fe8b on jens-na:include-variable-liquid-filters into 12a55b8 on jekyll:master.

[parkr]

Looking great! Would you please add a test for multiple filters so we know that one works, too? :)

[jens-na]

Do you mean a cucumber test?
I have already added several tests in test/test_tags.rb (including a test for multiple filters)

Specifically I test something like this:

---
include3: INCLUDE
---
{% include {{ page.include3 | downcase | append: '.html' }} %}

[parkr]

Indeed! Thanks.

This LGTM. @mattr-?