forloop.first ambiguity with offset

[sebastienros]

If offset is defined, what should first represent? The first item of the collection or the first iteration element? Same with offset: continue.

[jg-rp]

Hi,

I've found forloop.first and forloop.last to be the first and last iteration of the loop, not the first and last item in the underlying collection. For example:

Template

{% assign array = '1,2,3,4' | split: ',' -%}
{% for item in array limit: 1 -%}
a{{ item }} {{ forloop.first }} {{ forloop.last }}
{% endfor -%}
{% for item in array offset: continue -%}
b{{ item }} {{ forloop.first }} {{ forloop.last }}
{% endfor %}

Expected output

a1 true true
b2 true false
b3 false false
b4 false true

forloop.length behaves similarly.

Template

{% for item in (1..6) limit: 2 -%}
  a{{ item }}-{{ forloop.length }},
{%- endfor -%}
{% for item in (1..6) offset: continue -%}
  b{{ item }}-{{ forloop.length }},
{%- endfor -%}

Expected output

a1-2,a2-2,b3-4,b4-4,b5-4,b6-4,

You might also be interested in the test cases defined here. All of which pass using Ruby Liquid version 5.1.0.

Kindest regards, James

[sebastienros]

Thanks @jg-rp for the test cases. Do you know what is the rule to relate loops between each others? For instance what if there is a loop on (1..6) then the next loop is on (5..9), should continue start from the previous index? Or does it have to match the same value to be a continuation?

[jg-rp]

I believe the name of the loop variable and a string representation of the target collection or range are used to distinguish one loop from another.

Ruby Liquid uses a hyphen to separate the two. So an offset for {% for x in y limit: 2 %} would use the key "x-y", and {% for item in (1..6) limit: 3 %} would be "item-(1..6)".

Note that this approach disregards the contents of the target collection. Consider this template that reassigns foo between loops.

{% assign foo = '1,2,3,4,5,6' | split: ',' -%}
{% for item in foo limit: 3 -%}
  {{ item -}} 
{% endfor -%}
{% assign foo = 'u,v,w,x,y,z' | split: ',' -%}
{% for item in foo offset: continue -%}
{{ item -}}
{% endfor -%}

Output

123xyz

[sebastienros]

Awesome. In my current implementation I am only doing it for identifiers, so this is something else to fix. More features than whatever people are using or aware of even of though.

[sebastienros]

Related, there is a forloop.name property that should contain the token used by the loop.

https://github.com/harttle/liquidjs/commit/6dc7fada72467418806c1ee4bd7eaf3003690fe6

https://github.com/jg-rp/liquid/commit/e4e902429e40b85a0b6401d1637f8c09d615c253