Twig indexpage add numeric in one single category - twig

Question

On a SaaS platform I try to create an indexpage/sitemap for a website with a lot of categories.
Since it's a SaaS platform I'm not able to use/create custom functions whatsoever.
It have to be done at the frontend.
What I try to do is divide a list of categories into a list divided in letters and digits.
So a category name starting with A will go in category "A", a category starting with a number (eg 18 years) will go in a category called "0-9". So I will get an indexpage like so:
[A]
- Alpha
- Anton
- etc..
[B]
- Beta
- Brave
- etc..
[C]
- Charlie
- Cooking
- etc..
[0-9]
- 1 year
- 20 years
- 99 years
- etc..
I managed to get this working for all letters. However it not always put numbers in the [0-9] category. My script sometimes create a seperate index for eg 0 or 7 etc. So like:
[0]
- 1 year
- 18 years
- etc..
[1]
- 2 years
- 22 years
Also the index number is wrong. So it shows 1 under 0 and 2 under 1. Instead of:
[0-9]
- 1 year
- 18 years
- 2 years
- 22 years
I just can't see why that is. So my question is how can I put [numeric] categories in a single categorie called [0-9] instead of having them in a seperate categorie?
My code upto now looks like (some filters are specific platform filters):
{# ---------------- BEGINING ------------------- #}
{% set all_categories = [] %}
{% for category in shop.categories %}
{% set all_categories = all_categories | merge({ (0): category }) %}
{% for sub in category.subs %}
{% set all_categories = all_categories | merge({ (0): sub }) %}
{% for sub_sub in sub.subs %}
{% set all_categories = all_categories | merge({ (0): sub_sub }) %}
{% for sub_sub_sub in sub_sub.subs %}
{% set all_categories = all_categories | merge({ (0): sub_sub_sub }) %}
{% endfor %}
{% endfor %}
{% endfor %}
{% endfor %}
{% set categories = all_categories %}
{# ---------------- SORT LOGIC ------------------- #}
{# 'categories' array will be sorted and saved as 'grouped_categories' variable #}
{% set sorted_categories = [] %}
{% for key in categories | keys %}
{% set sorted_categories = sorted_categories | merge({ (key): categories[key].title }) %}
{% endfor %}
{% set sorted_categories = sorted_categories | sort %}
{% set first_letter = '' %}
{% set grouped_categories = [] %}
{% set new_group = [] %}
{% for i in sorted_categories | keys %}
{% if(categories[i].title) %}
{% set currect_first_letter = categories[i].title | first | upper %}
{% if(currect_first_letter != first_letter) %}
{% if(new_group) %}
{% set grouped_categories = grouped_categories | merge({ (first_letter): new_group }) %}
{% endif %}
{% set first_letter = currect_first_letter %}
{% set new_group = [categories[i]] %}
{% else %}
{% set new_group = new_group | merge({ (0): categories[i] }) %}
{% endif %}
{% endif %}
{% endfor %}
{% set grouped_categories = grouped_categories | merge({ (first_letter): new_group }) %}
{# ---------------- USING ------------------- #}
<div class="single-letter">
<span class="custom-title">{{ "All themes" }}:</span>
<ul>
{% for letter in grouped_categories[1:] | keys %}
<li>{{ letter }}</li>
{% endfor %}
{% for letter in grouped_categories[:1] | keys %}
<li>{{ '0-9' }}</li>
{% endfor %}
</ul>
</div>
{% for letter in grouped_categories[1:] | keys %}
<div id="letter-{{letter}}" class="letter-wrap">
<h3 class="title">{{ letter }}</h3>
<div class="group">
<ul>
{% for category in grouped_categories[letter] %}
<li>{{ category.title }}</li>
{% endfor %}
</ul>
</div>
</div>
{% endfor %}
{% for letter in grouped_categories[:1] | keys %}
<div id="letter-{{letter}}" class="letter-wrap">
<h3 class="title">{{ '0-9' }}</h3>
<div class="group">
<ul>
{% for category in grouped_categories[letter] %}
<li>{{ category.title }}</li>
{% endfor %}
</ul>
</div>
</div>
{% endfor %}
{# ---------------- THE END ------------------- #}
UPDATE AS PER REQUEST
Updated code
{% for category in categories %}
{% set currect_first_letter = category | first | upper %}
{% if currect_first_letter in [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] %}
{% set currect_first_letter = '0-9' %}
{% endif %}
{% if not (currect_first_letter in (grouped_categories | keys)) %}
{% set grouped_categories = grouped_categories | merge({ (currect_first_letter): [], }) %}
{% endif %}
{% set grouped_categories = grouped_categories | merge({ (currect_first_letter) : grouped_categories[currect_first_letter] | merge([ category, ]), }) %}
{% endfor %}
{#{% set sorted_categories = [] %}
{% for key in categories | keys %}
{% set sorted_categories = sorted_categories | merge({ (key): categories[key].title }) %}
{% endfor %}
{% set sorted_categories = sorted_categories | sort %}
{% set first_letter = '' %}
{% set grouped_categories = [] %}
{% set new_group = [] %}
{% for i in sorted_categories | keys %}
{% if(categories[i].title) %}
{% set currect_first_letter = categories[i].title | first | upper %}
{% if(currect_first_letter != first_letter) %}
{% if(new_group) %}
{% set grouped_categories = grouped_categories | merge({ (first_letter): new_group }) %}
{% endif %}
{% set first_letter = currect_first_letter %}
{% set new_group = [categories[i]] %}
{% else %}
{% set new_group = new_group | merge({ (0): categories[i] }) %}
{% endif %}
{% endif %}
{% endfor %}
{% set grouped_categories = grouped_categories | merge({ (first_letter): new_group }) %}#}
This has as result:
The merge filter only works with arrays or hashes; NULL and array given in....

Answer 1

You should be able to solve this if you override the currect_first_letter.
{% set currect_first_letter = categories[i].title | first | upper %}
{% if currect_first_letter in [0, 1, 2, 3, 4, 5, 6, 7, 8 , 9, ] %}
{% set currect_first_letter = '0-9' %} {# change to same group #}
{% endif %}
demo
Okay I've gone over your code and simplified the grouping process a bit.
Here is the code I would use to combine arrays in twig
{% set grouped_categories = [] %}
{% for category in categories %}
{% set currect_first_letter = category | first | upper %}
{# ----- ADDED THIS LINE ------- #}
{% if currect_first_letter in [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] %}
{% set currect_first_letter = '0-9' %}
{% endif %}
{# ----------------------------- #}
{% if not (currect_first_letter in (grouped_categories | keys)) %}
{% set grouped_categories = grouped_categories | merge({ (currect_first_letter): [], }) %}
{% endif %}
{% set grouped_categories = grouped_categories | merge({ (currect_first_letter) : grouped_categories[currect_first_letter] | merge([ category, ]), }) %}
{% endfor %}
Validation purpose:
{% for key in grouped_categories|keys %}
Key: {{ key }}
Values:
{% for value in grouped_categories[key] %}
- {{ value }}
{% endfor %}
{% endfor %}
demo
It seems if you use var in [0, 1, ...], before twig 3.X the 0 will return a false positive.
Try to use your original code, the one where everything got grouped in [0-9], but with the following statement
{% if currect_first_letter in [1, 2, 3, 4, 5, 6, 7, 8, 9] or currect_first_letter == '0' %}