Adam Ralph

A blog about how software development fills in the gaps between snowboarding


Blog Post Excerpts - A New Solution

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Something weird happened in the last few days with the Liquid template engine used for GitHub pages.

Previously (last push on 06 Jan), I was using the following code to generate excerpts of each post on the home page (source).

{% capture excerpt %}
  {% for paragraph in post.content %}
    {% if forloop.index0 <= post.excerpt %}
      {{ paragraph }}
    {% endif %}
  {% endfor %}
{% endcapture %}
{{ excerpt }}

This uses a YAML variable excerpt in each post which states how many paragraphs to include.

This morning, after I pushed an unrelated change, this code no longer worked and the entire content of each post was being shown on the homepage. I reported the issue to GitHub support but at the time of writing I have not yet received a reply.

(Brief interlude for day job.)

After coming home from work this evening and investigating further, I noticed that Henrik Andersson had changed his code to use truncation instead. This seemed like a viable alternative but I didn’t like the way each post was potentially truncated mid-word or mid-sentence depending on its content.

Then it struck me - why not combine the two approaches, so that each post still has a variable stating how long the excerpt should be but instead of being a paragraph count, make it a character count? So I changed the excerpt variables in each post accordingly and changed the template code to the following (source).

{{ post.content | truncate: post.excerpt, '' }}

Not only much simpler, but immune to the recent changes made to the GitHub pages Liquid engine! (In case you’re wondering, the second truncate parameter controls the suffix, which defaults to ‘…’.)

And normal service resumes…

Update 12 Jan 2013

Yesterday I received a reply from GitHub support with a link to an alternate solution which I think is much nicer (the second solution in the post). With this solution, the excerpt YAML variable is no longer needed. Instead, the following comment is inserted into each post to signify the end of the excerpt.

<!--excerpt-->

And the template code is changed to the following (source).

{{ post.content | split:'<!--excerpt-->' | first }}

Thanks very much to David Graham from GitHub.

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