vanilla-hugo/layouts/shortcodes/message.html

<span class="message side-{{ .Get 0 }}">
    <span class="message-sender">
        {{- if (eq (.Get 1) "reader") -}}
        {{- partial "icon.html" "moon" -}}
        {{- else -}}
        {{- partial "icon.html" "sun" -}}
        {{- end -}}
    </span>
    <span class="message-text">{{- .Inner -}}</span>
</span>