Test array filters added in Shopify/Liquid v5.7.2

[jg-rp]

This PR adds test cases for the following filters as they appear in version 5.7.2 of Shopify/Liquid.

• reject
• has
• find
• find_index

Note that these filters do not currently support arguments for testing/selecting child properties at arbitrary depths.

See Shopify/liquid#1906 and harttle/liquidjs#799

Some observations that hold true for all array filters (as of v5.7.2).

Optional argument

The second argument, target_value, is optional and it does not need to be a string, contrary to what the doc comments say.

Explicit nil

Explicitly testing for null/nil/None is not supported. Shopify/Liquid does not distinguish between the default value of nil and an explicit nil/null. For example, all templates are equivalent.

{{ a | has: 'foo' }}

{{ a | has: 'foo', nil}}

{{ a | has: 'foo', nosuchthing }}

Left values

Inputs are intended/assumed to be arrays of objects/hashes. If the input is an object/hash or primitive value (int, float, string, bool), it gets coerced to a single element array with the input value being the only item. With context data

{
    "a": [ {"foo": 42} ],
    "b": {"foo": 42}
}

Both of these templates are equivalent.

{{ a | find: 'foo' }}

{{ b | find: 'foo' }}

Arrays of strings

In Ruby, subscripting a string with another will return a substring if the first string contains the second. This leads to the following two templates resulting in true. There's at least one test case covering this behaviour in Shopify/Liquid, so this is known.

{{ 'foo' | has: 'oo' }}

{{ 'foo,bar' | split: ',' | has: 'oo' }}

And some odd results when filtering arrays of string values.

{{ 'x,y,cat' | split: ',' | reject: 'c' | join: ', ' }}

Early termination

If the input array contains a nil/null/None before a successful match, the result is nil/null/None. This example renders nothing when a is equal to ["x", nil, "z"].

{{ a | has: 'z' }}

Note that the where filter prior to version 5.7 behaved the same way.

Problematic integers

An exception is raised if the input array contains an integer and target_value is a string. And testing an input array of integers against an integer gives some as yet unexplained results.

require 'liquid'

source = <<LIQUID
{{ some_array | find: 3 }}
{{ some_array | find_index: 1 }}
LIQUID

template = Liquid::Template.parse(source, error_mode: :lax)
puts template.render!("some_array" => [-1, 42, 1, 2, 3, 4])