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Validating Liquid Template Processing and Resource Management in Shopify/liquid

This test suite validates the core functionality of Liquid template parsing, rendering, and resource management. It covers template context handling, variable assignments, and error management in the Shopify Liquid templating engine.

Test Coverage Overview

The test suite provides comprehensive coverage of Liquid template functionality, including:

Template parsing and rendering behavior
Variable assignment persistence across renders
Resource limit handling and memory management
Context and drop object interactions
Error handling and undefined variable management

Implementation Analysis

The testing approach utilizes Minitest framework with a focus on isolation and edge cases. Tests are structured to verify template behavior across multiple scenarios including resource limits, encoding issues, and variable scope management. Key patterns include mock drops, custom assigns, and exception handling verification.

Technical Details

Testing tools and configuration:

Minitest as the testing framework
Custom drop classes for context testing
Resource limit configurations for memory testing
UTF-8 encoding validation
Exception renderer implementations

Best Practices Demonstrated

The test suite exemplifies strong testing practices including:

Comprehensive edge case coverage
Isolation of test scenarios
Clear test naming conventions
Thorough error condition testing
Resource limit verification

shopify/liquid

test/integration/template_test.rb

            
# frozen_string_literal: true

require 'test_helper'
require 'timeout'

class TemplateContextDrop < Liquid::Drop
  def liquid_method_missing(method)
    method
  end

  def foo
    'fizzbuzz'
  end

  def baz
    @context.registers['lulz']
  end
end

class SomethingWithLength < Liquid::Drop
  def length
    nil
  end
end

class ErroneousDrop < Liquid::Drop
  def bad_method
    raise 'ruby error in drop'
  end
end

class DropWithUndefinedMethod < Liquid::Drop
  def foo
    'foo'
  end
end

class TemplateTest < Minitest::Test
  include Liquid

  def test_instance_assigns_persist_on_same_template_object_between_parses
    t = Template.new
    assert_equal('from instance assigns', t.parse("{% assign foo = 'from instance assigns' %}{{ foo }}").render!)
    assert_equal('from instance assigns', t.parse("{{ foo }}").render!)
  end

  def test_warnings_is_not_exponential_time
    str = "false"
    100.times do
      str = "{% if true %}true{% else %}#{str}{% endif %}"
    end

    t = Template.parse(str)
    assert_equal([], Timeout.timeout(1) { t.warnings })
  end

  def test_instance_assigns_persist_on_same_template_parsing_between_renders
    t = Template.new.parse("{{ foo }}{% assign foo = 'foo' %}{{ foo }}")
    assert_equal('foo', t.render!)
    assert_equal('foofoo', t.render!)
  end

  def test_custom_assigns_do_not_persist_on_same_template
    t = Template.new
    assert_equal('from custom assigns', t.parse("{{ foo }}").render!('foo' => 'from custom assigns'))
    assert_equal('', t.parse("{{ foo }}").render!)
  end

  def test_custom_assigns_squash_instance_assigns
    t = Template.new
    assert_equal('from instance assigns', t.parse("{% assign foo = 'from instance assigns' %}{{ foo }}").render!)
    assert_equal('from custom assigns', t.parse("{{ foo }}").render!('foo' => 'from custom assigns'))
  end

  def test_persistent_assigns_squash_instance_assigns
    t = Template.new
    assert_equal('from instance assigns', t.parse("{% assign foo = 'from instance assigns' %}{{ foo }}").render!)
    t.assigns['foo'] = 'from persistent assigns'
    assert_equal('from persistent assigns', t.parse("{{ foo }}").render!)
  end

  def test_lambda_is_called_once_from_persistent_assigns_over_multiple_parses_and_renders
    t = Template.new
    t.assigns['number'] = -> {
      @global ||= 0
      @global  += 1
    }
    assert_equal('1', t.parse("{{number}}").render!)
    assert_equal('1', t.parse("{{number}}").render!)
    assert_equal('1', t.render!)
    @global = nil
  end

  def test_lambda_is_called_once_from_custom_assigns_over_multiple_parses_and_renders
    t = Template.new
    assigns = {
      'number' => -> {
        @global ||= 0
        @global += 1
      },
    }
    assert_equal('1', t.parse("{{number}}").render!(assigns))
    assert_equal('1', t.parse("{{number}}").render!(assigns))
    assert_equal('1', t.render!(assigns))
    @global = nil
  end

  def test_resource_limits_works_with_custom_length_method
    t = Template.parse("{% assign foo = bar %}")
    t.resource_limits.render_length_limit = 42
    assert_equal("", t.render!("bar" => SomethingWithLength.new))
  end

  def test_resource_limits_render_length
    t = Template.parse("0123456789")
    t.resource_limits.render_length_limit = 9
    assert_equal("Liquid error: Memory limits exceeded", t.render)
    assert(t.resource_limits.reached?)

    t.resource_limits.render_length_limit = 10
    assert_equal("0123456789", t.render!)
  end

  def test_resource_limits_render_score
    t = Template.parse("{% for a in (1..10) %} {% for a in (1..10) %} foo {% endfor %} {% endfor %}")
    t.resource_limits.render_score_limit = 50
    assert_equal("Liquid error: Memory limits exceeded", t.render)
    assert(t.resource_limits.reached?)

    t = Template.parse("{% for a in (1..100) %} foo {% endfor %}")
    t.resource_limits.render_score_limit = 50
    assert_equal("Liquid error: Memory limits exceeded", t.render)
    assert(t.resource_limits.reached?)

    t.resource_limits.render_score_limit = 200
    assert_equal((" foo " * 100), t.render!)
    refute_nil(t.resource_limits.render_score)
  end

  def test_resource_limits_aborts_rendering_after_first_error
    t = Template.parse("{% for a in (1..100) %} foo1 {% endfor %} bar {% for a in (1..100) %} foo2 {% endfor %}")
    t.resource_limits.render_score_limit = 50
    assert_equal("Liquid error: Memory limits exceeded", t.render)
    assert(t.resource_limits.reached?)
  end

  def test_resource_limits_hash_in_template_gets_updated_even_if_no_limits_are_set
    t = Template.parse("{% for a in (1..100) %}x{% assign foo = 1 %} {% endfor %}")
    t.render!
    assert(t.resource_limits.assign_score > 0)
    assert(t.resource_limits.render_score > 0)
  end

  def test_render_length_persists_between_blocks
    t = Template.parse("{% if true %}aaaa{% endif %}")
    t.resource_limits.render_length_limit = 3
    assert_equal("Liquid error: Memory limits exceeded", t.render)
    t.resource_limits.render_length_limit = 4
    assert_equal("aaaa", t.render)

    t = Template.parse("{% if true %}aaaa{% endif %}{% if true %}bbb{% endif %}")
    t.resource_limits.render_length_limit = 6
    assert_equal("Liquid error: Memory limits exceeded", t.render)
    t.resource_limits.render_length_limit = 7
    assert_equal("aaaabbb", t.render)

    t = Template.parse("{% if true %}a{% endif %}{% if true %}b{% endif %}{% if true %}a{% endif %}{% if true %}b{% endif %}{% if true %}a{% endif %}{% if true %}b{% endif %}")
    t.resource_limits.render_length_limit = 5
    assert_equal("Liquid error: Memory limits exceeded", t.render)
    t.resource_limits.render_length_limit = 6
    assert_equal("ababab", t.render)
  end

  def test_render_length_uses_number_of_bytes_not_characters
    t = Template.parse("{% if true %}すごい{% endif %}")
    t.resource_limits.render_length_limit = 8
    assert_equal("Liquid error: Memory limits exceeded", t.render)
    t.resource_limits.render_length_limit = 9
    assert_equal("すごい", t.render)
  end

  def test_default_resource_limits_unaffected_by_render_with_context
    context = Context.new
    t = Template.parse("{% for a in (1..100) %}x{% assign foo = 1 %} {% endfor %}")
    t.render!(context)
    assert(context.resource_limits.assign_score > 0)
    assert(context.resource_limits.render_score > 0)
  end

  def test_can_use_drop_as_context
    t = Template.new
    t.registers['lulz'] = 'haha'
    drop = TemplateContextDrop.new
    assert_equal('fizzbuzz', t.parse('{{foo}}').render!(drop))
    assert_equal('bar', t.parse('{{bar}}').render!(drop))
    assert_equal('haha', t.parse("{{baz}}").render!(drop))
  end

  def test_render_bang_force_rethrow_errors_on_passed_context
    context = Context.new('drop' => ErroneousDrop.new)
    t = Template.new.parse('{{ drop.bad_method }}')

    e = assert_raises(RuntimeError) do
      t.render!(context)
    end
    assert_equal('ruby error in drop', e.message)
  end

  def test_exception_renderer_that_returns_string
    exception = nil
    handler   = ->(e) {
      exception = e
      '<!-- error -->'
    }

    output = Template.parse("{{ 1 | divided_by: 0 }}").render({}, exception_renderer: handler)

    assert(exception.is_a?(Liquid::ZeroDivisionError))
    assert_equal('<!-- error -->', output)
  end

  def test_exception_renderer_that_raises
    exception = nil
    assert_raises(Liquid::ZeroDivisionError) do
      Template.parse("{{ 1 | divided_by: 0 }}").render({}, exception_renderer: ->(e) {
                                                                                 exception = e
                                                                                 raise
                                                                               })
    end
    assert(exception.is_a?(Liquid::ZeroDivisionError))
  end

  def test_global_filter_option_on_render
    global_filter_proc = ->(output) { "#{output} filtered" }
    rendered_template  = Template.parse("{{name}}").render({ "name" => "bob" }, global_filter: global_filter_proc)

    assert_equal('bob filtered', rendered_template)
  end

  def test_global_filter_option_when_native_filters_exist
    global_filter_proc = ->(output) { "#{output} filtered" }
    rendered_template  = Template.parse("{{name | upcase}}").render({ "name" => "bob" }, global_filter: global_filter_proc)

    assert_equal('BOB filtered', rendered_template)
  end

  def test_undefined_variables
    t      = Template.parse("{{x}} {{y}} {{z.a}} {{z.b}} {{z.c.d}}")
    result = t.render({ 'x' => 33, 'z' => { 'a' => 32, 'c' => { 'e' => 31 } } }, strict_variables: true)

    assert_equal('33  32  ', result)
    assert_equal(3, t.errors.count)
    assert_instance_of(Liquid::UndefinedVariable, t.errors[0])
    assert_equal('Liquid error: undefined variable y', t.errors[0].message)
    assert_instance_of(Liquid::UndefinedVariable, t.errors[1])
    assert_equal('Liquid error: undefined variable b', t.errors[1].message)
    assert_instance_of(Liquid::UndefinedVariable, t.errors[2])
    assert_equal('Liquid error: undefined variable d', t.errors[2].message)
  end

  def test_nil_value_does_not_raise
    t      = Template.parse("some{{x}}thing", error_mode: :strict)
    result = t.render!({ 'x' => nil }, strict_variables: true)

    assert_equal(0, t.errors.count)
    assert_equal('something', result)
  end

  def test_undefined_variables_raise
    t = Template.parse("{{x}} {{y}} {{z.a}} {{z.b}} {{z.c.d}}")

    assert_raises(UndefinedVariable) do
      t.render!({ 'x' => 33, 'z' => { 'a' => 32, 'c' => { 'e' => 31 } } }, strict_variables: true)
    end
  end

  def test_undefined_drop_methods
    d = DropWithUndefinedMethod.new
    t = Template.new.parse('{{ foo }} {{ woot }}')
    result = t.render(d, strict_variables: true)

    assert_equal('foo ', result)
    assert_equal(1, t.errors.count)
    assert_instance_of(Liquid::UndefinedDropMethod, t.errors[0])
  end

  def test_undefined_drop_methods_raise
    d = DropWithUndefinedMethod.new
    t = Template.new.parse('{{ foo }} {{ woot }}')

    assert_raises(UndefinedDropMethod) do
      t.render!(d, strict_variables: true)
    end
  end

  def test_undefined_filters
    t = Template.parse("{{a}} {{x | upcase | somefilter1 | somefilter2 | somefilter3}}")
    filters = Module.new do
      def somefilter3(v)
        "-#{v}-"
      end
    end
    result = t.render({ 'a' => 123, 'x' => 'foo' }, filters: [filters], strict_filters: true)

    assert_equal('123 ', result)
    assert_equal(1, t.errors.count)
    assert_instance_of(Liquid::UndefinedFilter, t.errors[0])
    assert_equal('Liquid error: undefined filter somefilter1', t.errors[0].message)
  end

  def test_undefined_filters_raise
    t = Template.parse("{{x | somefilter1 | upcase | somefilter2}}")

    assert_raises(UndefinedFilter) do
      t.render!({ 'x' => 'foo' }, strict_filters: true)
    end
  end

  def test_using_range_literal_works_as_expected
    source = "{% assign foo = (x..y) %}{{ foo }}"
    assert_template_result("1..5", source, { "x" => 1, "y" => 5 })

    source = "{% assign nums = (x..y) %}{% for num in nums %}{{ num }}{% endfor %}"
    assert_template_result("12345", source, { "x" => 1, "y" => 5 })
  end

  def test_source_string_subclass
    string_subclass = Class.new(String) do
      # E.g. ActiveSupport::SafeBuffer does this, so don't just rely on to_s to return a String
      def to_s
        self
      end
    end
    source = string_subclass.new("{% assign x = 2 -%} x= {{- x }}")
    assert_instance_of(string_subclass, source)
    output = Template.parse(source).render!
    assert_equal("x=2", output)
    assert_instance_of(String, output)
  end

  def test_raises_error_with_invalid_utf8
    e = assert_raises(TemplateEncodingError) do
      Template.parse(<<~LIQUID)
        {% comment %}
          \xC0
        {% endcomment %}
      LIQUID
    end

    assert_equal('Liquid error: Invalid template encoding', e.message)
  end

  def test_allows_non_string_values_as_source
    assert_equal('', Template.parse(nil).render)
    assert_equal('1', Template.parse(1).render)
    assert_equal('true', Template.parse(true).render)
  end
end