Styling Hakyll Tags

Posted on October 13, 2019 | blog setup haskell hakyll

This blog is generated using Hakyll. Hakyll provides a way to annotate posts with tags and generate a list of pages with the same tag. I followed the excellent guide from and added the tags feature to the blog. The html produced for the tags is quite bare

<a href="../../tags/blog%20setup.html">blog setup</a>,
<a href="../../tags/haskell.html">haskell</a>,
<a href="../../tags/hakyll.html">hakyll</a>

blog setup, haskell, hakyll

and I wanted to style it using bulma “is-link” and “tag” attributes.

<a href="../../tags/blog%20setup.html" class="tag is-link">blog setup</a>
<a href="../../tags/haskell.html" class="tag is-link">haskell</a>
<a href="../../tags/hakyll.html" class="tag is-link">hakyll</a>

blog setup haskell hakyll

While this can be done with jquery after the page is loaded, I wanted to do the styling during site generation. I took this as an opportunity to play with Hakyll.

The html for the tags is added to the Hakyll post context by the tagsField function.

postCtxWithTags :: Tags -> Context String
postCtxWithTags tags = tagsField "tags" tags `mappend` postCtx

Hakyll also offers a tagsFieldWith function where the HTML generation can be customized. Below is the code I ended up with.

postCtxWithTags :: Tags -> Context String
postCtxWithTags tags = tagsFieldBulma "tags" tags `mappend` postCtx

tagsFieldBulma :: String -> Tags -> Context a
tagsFieldBulma =
  tagsFieldWith getTags simpleRenderLinkBulma (mconcat . intersperse " ")

simpleRenderLinkBulma :: String -> (Maybe FilePath) -> Maybe H.Html
simpleRenderLinkBulma _ Nothing = Nothing
simpleRenderLinkBulma tag (Just filePath) =
  Just $ H.a ! A.href (toValue $ toUrl filePath) ! A.class_ "tag is-link" $ toHtml tag

This snippet custmoizes the simpleRenderLink function to add tag is-link attributes to the tags. This function is plugged into tagsFieldBulma which gets plugged into postCtxWithTags. The link to full source is here Tags.hs.