not_working.rb

require "bundler/inline"

gemfile do
  source "https://rubygems.org"

  ruby "2.7.3"

  gem "liquid", "5.0.1", require: false
  gem 'liquid-c', github: 'Shopify/liquid-c', ref: 'fb25228', require: false
end

require "liquid/c"
require "liquid"

variables = { 'name' => 'Rafael' }

template = Liquid::Template.new
template.parse('{{ name | unknown }}', error_mode: :strict)
puts template.render!(variables, strict_variables: true, strict_filters: true)
# Rafael

working.rb

require "bundler/inline"

gemfile do
  source "https://rubygems.org"

  ruby "2.7.3"

  gem "liquid", "5.0.1", require: false
  gem 'liquid-c', github: 'Shopify/liquid-c', ref: 'fef8329', require: false
end

require "liquid/c"
require "liquid"

variables = { 'name' => 'Rafael' }

template = Liquid::Template.new
template.parse('{{ name | unknown }}', error_mode: :strict)
puts template.render!(variables, strict_variables: true, strict_filters: true)
# Traceback (most recent call last):
# 	4: from working.rb:16:in `<main>'
# 	3: from /Users/rafael/.gem/ruby/2.7.3/gems/liquid-5.0.1/lib/liquid/template.rb:205:in `render!'
# 	2: from /Users/rafael/.gem/ruby/2.7.3/gems/liquid-5.0.1/lib/liquid/template.rb:195:in `render'
# 	1: from /Users/rafael/.gem/ruby/2.7.3/gems/liquid-5.0.1/lib/liquid/document.rb:41:in `render_to_output_buffer'
# /Users/rafael/.gem/ruby/2.7.3/gems/liquid-5.0.1/lib/liquid/document.rb:41:in `render_to_output_buffer': Liquid error: undefined filter unknown (Liquid::UndefinedFilter)