Jekyll: Erro de sintaxe líquida

• [ ] Acredito que isso seja um bug, não uma pergunta sobre o uso do Jekyll.
• [x] Atualizei para o Jekyll mais recente (ou) se estiver nas páginas do GitHub para o github-pages mais recente
• [x] Eu li o arquivo CONTRIBUTION em https://jekyllrb.com/docs/contributing/
• [ ] Esta é uma solicitação de recurso.

• [ ] Estou em (ou testei) _macOS _ 10+
• [x] Estou em (ou testei) _Debian/Ubuntu _ GNU/Linux
• [ ] Estou no (ou testei) _Fedora _ GNU/Linux
• [ ] Estou em (ou testei em) _Arch _ GNU/Linux
• [ ] Estou em (ou testei) _Other _ GNU/Linux
• [ ] Estou em (ou testei) _Windows _ 10+

• [ ] Eu estava tentando instalar.
• [ ] Há uma API de plug-in quebrada.
• [ ] Tive um erro no GitHub Pages e o reproduzi localmente.
• [ ] Tive um erro no GitHub Pages, e o suporte do GitHub disse que era um Jekyll Bug.
• [ ] Tive um erro no GitHub Pages e não testei localmente.
• [ ] Eu estava tentando construir.
• [x] Era outro bug.
  

  Minhas etapas de reprodução

Estou recebendo o seguinte aviso durante a compilação, como posso corrigir isso

Liquid Warning: Liquid syntax error (line 5): Expected id but found open_square in "item in site.[item.label]" in feeds/feed.json
    Liquid Warning: Liquid syntax error (line 19): Expected id but found open_square in "post in site.categories.[page.category]" in /_layouts/category.html
    Liquid Warning: Liquid syntax error (line 19): Expected id but found open_square in "post in site.categories.[page.category]" in /_layouts/category.html
    Liquid Warning: Liquid syntax error (line 19): Expected id but found open_square in "post in site.categories.[page.category]" in /_layouts/category.html
    Liquid Warning: Liquid syntax error (line 19): Expected id but found open_square in "post in site.categories.[page.category]" in /_layouts/category.html
    Liquid Warning: Liquid syntax error (line 19): Expected id but found open_square in "post in site.categories.[page.category]" in /_layouts/category.html
    Liquid Warning: Liquid syntax error (line 19): Expected id but found open_square in "post in site.categories.[page.category]" in /_layouts/category.html
    Liquid Warning: Liquid syntax error (line 19): Expected id but found open_square in "post in site.categories.[page.category]" in /_layouts/category.html
    Liquid Warning: Liquid syntax error (line 19): Expected id but found open_square in "post in site.categories.[page.category]" in /_layouts/category.html
    Liquid Warning: Liquid syntax error (line 19): Expected id but found open_square in "post in site.categories.[page.category]" in /_layouts/category.html

categoria.html

<h1 class="title">{{ page.title }}</h1>

{% unless page.content == '' %}
  <p>{{ page.content }}</p>
{% endunless %}
<ul id="blog-posts" class="posts">
{% for post in site.categories.[page.category] %}
  <li><span>{{ post.date | date: "%d/%m/%Y" }} &raquo;</span><a href="{{ post.url }}">{{ post.title }}</a></li>
{% endfor %}
</ul>

feed.json

{% assign first = true %}
[
{% for collection in site.collections %}
    {% for item in collection %}
        {% for item in site.[item.label] %}
            {% if item.title != null and item.title != empty %}
            {% unless first %},{% endunless %}{
                "title": {{item.title | jsonify}},
                "content": {{item.content | markdownify | strip_html | jsonify}},
                "link": "{{ site.baseurl }}{{ item.url }}",
                "date": "{{ item.date }}",
                "excerpt": "{{ item.snippet }}",
                "search_omit": "{{ item.search_omit }}"
            }
            {% assign first = false %}
            {% endif %}
        {% endfor %}
    {% endfor %}
{% endfor %}


{% for post in site.posts %}
    {% if post.title != null and post.title != empty %}
    {% unless first %},{% endunless %}{
        "title": {{post.title | jsonify}},
        "content": {{post.content | markdownify | strip_html | jsonify}},
        "link": "{{ site.baseurl }}{{ post.url }}",
        "date": "{{ post.date }}",
        "excerpt": "{{ post.snippet }}",
        "search_omit": "{{ post.search_omit }}"
    }
    {% assign first = false %}
    {% endif %}
{% endfor %}

{% for page in site.pages %}
    {% if page.title != null and page.title != empty %}
    {% unless first %},{% endunless %}{
        "title": {{page.title | jsonify}},
        "content": {{page.content | strip_html | jsonify}},
        "link": "{{ site.baseurl }}{{ page.url | replace: 'index.html', '' }}",
        "date": {{ page.date | jsonify }},
        "excerpt": {{ page.description | jsonify }},
        "search_omit": "{{ page.search_omit }}"
    }
    {% assign first = false %}
    {% endif %}
{% endfor %}
]