los campos pueden ser obligatorios

app/assets/javascripts/validation.js

@@ -0,0 +1,12 @@
+$(document).on('turbolinks:load', function() {
+  $('#submit-post').click(function(e) {
+    var form = $(this).parents('form.form');
+
+    if (form[0].checkValidity() === false) {
+      e.preventDefault();
+      e.stopPropagation();
+    }
+
+    form.addClass('was-validated');
+  });
+});

app/models/post/template_field.rb

@@ -10,9 +10,13 @@ class Post
       @contents = contents
     end
 
+    # Obtiene el valor
+    def value
+      complex? ? contents.dig('value') : contents
+    end
+
     def type
       return @type if @type
-      return unless simple?
 
       case
       when text_area?
@@ -79,11 +83,6 @@ class Post
       array?
     end
 
-    # Obtiene el valor
-    def value
-      complex? ? contents.dig('value') : contents
-    end
-
     # Obtiene los valores posibles para el campo de la plantilla
     def values
       return '' if %w[string text].include? value

app/views/posts/_form.haml

@@ -15,7 +15,7 @@
 - else
   - url = site_post_path(@site, @post, lang: @lang)
   - method = :patch
-= form_tag url, method: method, class: 'form' do
+= form_tag url, method: method, class: 'form', novalidate: true do
   .form-group
     = submit_tag t('posts.save'), class: 'btn btn-success'
   .form-group
@@ -85,9 +85,10 @@
       - when 'text'
         = text_field 'post', template,
           value: value,
-          class: 'form-control'
+          class: 'form-control',
+          required: template.required?
       - when 'text_area'
-        = text_area_tag name, value, class: 'form-control'
+        = text_area_tag name, value, class: 'form-control', required: template.required?
       - when 'check_box'
         = hidden_field 'post', template, value: 'false'
         = check_box_tag name, 'true', value == 'true', class: 'form-control'
@@ -95,5 +96,6 @@
         = select_tag name, options_for_select(template.values, @post.get_front_matter(template)),
           { class: 'form-control select2',
           multiple: template.multiple? }
+      .invalid-feedback= t('posts.invalid')
   .form-group
-    = submit_tag t('posts.save'), class: 'btn btn-success'
+    = submit_tag t('posts.save'), class: 'btn btn-success', id: 'submit-post'

config/locales/en.yml

@@ -202,4 +202,4 @@ en:
       file: "Couldn't write the file"
       title: 'Post needs a title'
       date: 'Post needs a valid date'
-
+    invalid: 'This field is required!'

config/locales/es.yml

@@ -198,3 +198,4 @@ es:
       file: 'No se pudo escribir el archivo'
       title: 'Necesita un título'
       date: 'Necesita una fecha'
+    invalid: '¡Este campo es obligatorio!'