twig merge error Unexpected token "punctuation" of value "[" - php

Question

My goal is having a string like "name: smoothie, ingredients: milk, orange, category: vegan" (there can be a lot option: value or option: value, value, value... pairs) to produce an array like the following
[
{
option: 'name',
value: ['smoothie']
},
{
option: 'ingredients',
value: ['milk', 'orange']
},
{
option: 'category',
value: ['vegan']
}
]
I thought something like the following would work but it produces the following error and i can't understand why.
The problem is in the line where i try to add a value to the existing options[last_ok_index].value array
{% set options[last_ok_index].value = options[last_ok_index].value|merge( [ x[0] ] ) %}
Unexpected token "punctuation" of value "[" ("end of statement block" expected).
{% set product = "name: smoothie, ingredients: milk, orange" %}
{% set options = [] %}
{% set last_ok_index = 0 %}
{% for item in product|split(',') %}
{% set x = item|split(': ') %}
{% if x|length == 2 %}
{% set options = options|merge( [ { option: x[0], value: [x[1]] } ] ) %}
{% set last_ok_index = loop.index - 1 %}
{% else %}
{% set options[last_ok_index].value = options[last_ok_index].value|merge( [ x[0] ] ) %}
{% endif%}
{% endfor %}
{# print result #}
{% for item in options %}
{{item.option }}
{% for inner_item in item.value %}
{{"-" ~ inner_item}}
{% endfor %}
{% endfor %}

Answer 1

You should go with the suggestion in the comments by #dbrumann and use a TwigExtension.
However if you want to solve this in pure twig, then you are overcomplicating things.
First things first, the problem already starts at your first split, your expected output is smoothie and ingredients, while the actual result will be smoothie, ingredients, orange. You can fix this by passiung asecond argument to the split filter, which will limit the output.
Split uses the PHP function explode in the background. More on what the second parameters does you can find in the documentation here
Now as I said you can simply your snippet by creating the "item" in two parts rather than one part
{% set product = "name: smoothie, ingredients: milk, orange" %}
{% set items = [] %}
{% for item in product|split(',', 2) %}
{% set tmp = item|split(':') %}
{% set option = tmp[0] %}
{% set values = [] %}
{% for value in tmp[1]|split(',') %}
{% set values = values|merge([ value, ]) %}
{% endfor %}
{% set items = items|merge([ {'option': option, 'values': values,}, ]) %}
{% endfor %}
demo
As you've changed the initial input of the original question. The problem still starts with the split filter. I'd suggest you use another delimeter for your values, e.g. ;
{% set product = 'name: smoothie 3, ingredients: milk ; orange; pineapple, category: bar' %}
{% set products = [] %}
{% for string in products_raw %}
{% set product = [] %}
{% for item in string|split(',') %}
{% set tmp = item|split(':') %}
{% set option = tmp[0] %}
{% set values = [] %}
{% for value in tmp[1]|split(';') %}
{% set values = values|merge([ value, ]) %}
{% endfor %}
{% set product = product|merge([ {'option': option, 'values': values,}, ]) %}
{% endfor %}
{% set products = products|merge([ product, ]) %}
{% endfor %}
{% for product in products %}
{% for item in product %}
- Option: {{ item.option }}
- Values:
{% for value in item.values %}
- {{value }}
{% endfor %}
{% endfor %}
----------------------------------
{% endfor %}
demo

Answer 2

Thank you a lot for all the tips, i changed the logic a bit and it works now.
I will search about twig extensions as you proposed since it is for sure too much code in twig for something like that.
{% set product = "name: smoothie, ingredients: milk, orange, sugar, tags: healthy, popular, category: milk" %}
{% set options = [] %}
{% set last_option = null %}
{% set last_value = null %}
{% for item in product|split(',') %}
{% set x = item|split(':') %}
{% if x|length == 2 %}
{% if last_value|length > 0 %}
{% set options = options|merge( [ {option: last_option, value: last_value} ] ) %}
{% endif %}
{% set last_option = x[0] %}
{% set last_value = [x[1]] %}
{% else %}
{% set last_value = last_value|merge([x[0]]) %}
{% endif%}
{% if loop.last %}
{% if last_value|length > 0 %}
{% set options = options|merge( [ {option: last_option, value: last_value} ] ) %}
{% endif %}
{% endif %}
{% endfor %}
{# print result #}
{% for item in options %}
{{ item.option }}
{% for inner_item in item.value %}
{{ "-" ~ inner_item }}
{% endfor %}
{% endfor %}