Initial commit

.gitignore

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+/.bundle/
+/.yardoc
+/_yardoc/
+/coverage/
+/doc/
+/pkg/
+/spec/reports/
+/tmp/
+
+*.gem
+Gemfile.lock
+
+.rubocop-https---shopify-github-io-ruby-style-guide-rubocop-yml

.rubocop.yml

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+inherit_from:
+  - 'https://shopify.github.io/ruby-style-guide/rubocop.yml'
+
+Metrics/MethodLength:
+  Enabled: false
+
+Layout/LineLength:
+  Enabled: false
+
+Lint/MissingSuper:
+  Enabled: false
+
+Style/FrozenStringLiteralComment:
+  Enabled: false

Gemfile

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+source "https://rubygems.org"
+
+git_source(:github) { |repo_name| "https://github.com/#{repo_name}" }
+
+# Specify your gem's dependencies in theme-check.gemspec
+gemspec
+
+gem 'bundler'
+gem 'rake'
+gem 'minitest'
+gem 'rubocop', require: false
+
+gem 'liquid', github: 'Shopify/liquid', branch: 'master'
+gem 'liquid-c', github: 'Shopify/liquid-c', branch: 'master'

Rakefile

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+require "rake/testtask"
+require 'rubocop/rake_task'
+
+Rake::TestTask.new(:test) do |t|
+  t.libs << "test"
+  t.libs << "lib"
+  t.test_files = FileList["test/**/*_test.rb"]
+end
+
+RuboCop::RakeTask.new
+
+task default: [:rubocop, :test]

exe/theme-check

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+#!/usr/bin/env ruby
+
+require "theme_check"
+
+path = ARGV[0] || abort("usage: theme-check theme/root/path")
+puts ThemeCheck.analyze(path)

lib/theme_check.rb

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+require "liquid/c"
+
+require_relative "theme_check/analyzer"
+require_relative "theme_check/check"
+require_relative "theme_check/checks"
+require_relative "theme_check/node"
+require_relative "theme_check/offense"
+require_relative "theme_check/tags"
+require_relative "theme_check/theme"
+require_relative "theme_check/visitor"
+
+Dir[__dir__ + "/theme_check/checks/*.rb"].each { |file| require file }
+
+module ThemeCheck
+  def self.analyze(theme_root)
+    analyzer = Analyzer.new(Theme.new(theme_root))
+    analyzer.analyze_theme
+    analyzer.offenses
+  end
+end

lib/theme_check/analyzer.rb

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+module ThemeCheck
+  class Analyzer
+    attr_reader :offenses
+
+    def initialize(theme, check_classes = Check.all)
+      @theme = theme
+      @offenses = []
+      @checks = Checks.new
+      check_classes.each do |check_class|
+        check = check_class.new
+        check.theme = @theme
+        check.offenses = @offenses
+        @checks << check
+      end
+      @visitor = Visitor.new(@checks)
+    end
+
+    def analyze_theme
+      @theme.all_files_paths.each { |template| analyze_template(template) }
+      @checks.call(:on_end)
+    end
+
+    def analyze_template(template_path)
+      template_path = Pathname(template_path)
+      template = Liquid::Template.parse(
+        template_path.read,
+        line_numbers: true,
+        disable_liquid_c_nodes: true
+      )
+      relative_template_path = template_path.relative_path_from(@theme.root)
+      @visitor.visit_template(template, path: relative_template_path)
+    end
+  end
+end

lib/theme_check/check.rb

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+module ThemeCheck
+  class Check
+    attr_accessor :theme
+    attr_accessor :offenses
+
+    SEVERITIES = [
+      :error,
+      :suggestion,
+      :style,
+    ]
+
+    class << self
+      def all
+        @all ||= []
+      end
+
+      def inherited(klass)
+        all << klass
+      end
+
+      def severity(severity = nil)
+        if severity
+          unless SEVERITIES.include?(severity)
+            raise ArgumentError, "unknown severity. Use: #{SEVERITIES.join(', ')}"
+          end
+          @severity = severity
+        end
+        @severity
+      end
+
+      def doc(doc = nil)
+        @doc = doc if doc
+        @doc
+      end
+    end
+
+    def severity
+      self.class.severity
+    end
+
+    def doc
+      self.class.doc
+    end
+
+    def ignore!
+      @ignored = true
+    end
+
+    def unignore!
+      @ignored = false
+    end
+
+    def ignored?
+      defined?(@ignored) && @ignored
+    end
+
+    def add_offense(message, node: nil, template: node&.template)
+      offenses << Offense.new(self, template, node, message)
+    end
+  end
+end

lib/theme_check/checks.rb

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+module ThemeCheck
+  class Checks < Array
+    def call(method, *args)
+      each do |check|
+        if check.respond_to?(method) && !check.ignored?
+          check.send(method, *args)
+        end
+      end
+    end
+  end
+end

lib/theme_check/checks/liquid_tag.rb

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+module ThemeCheck
+  # Recommends using {% liquid ... %} if 3 or more consecutive {% ... %} are found.
+  class LiquidTag < Check
+    severity :suggestion
+    doc "https://shopify.dev/docs/themes/liquid/reference/tags/theme-tags#liquid"
+
+    MIN_CONSECUTIVE_STATEMENTS = 4
+
+    def initialize
+      @first_statement = nil
+      @consecutive_statements = 0
+    end
+
+    def on_tag(node)
+      unless node.comment?
+        increment_consecutive_statements(node)
+      end
+    end
+
+    def on_string(node)
+      # Only reset the counter on outputted strings, and ignore empty line-breaks
+      if node.parent.block? && !node.value.strip.empty?
+        reset_consecutive_statements
+      end
+    end
+
+    def after_document(_node)
+      reset_consecutive_statements
+    end
+
+    def increment_consecutive_statements(node)
+      @first_statement ||= node
+      @consecutive_statements += 1
+    end
+
+    def reset_consecutive_statements
+      if @consecutive_statements >= MIN_CONSECUTIVE_STATEMENTS
+        add_offense("Use {% liquid ... %} to write multiple tags", node: @first_statement)
+      end
+      @first_statement = nil
+      @consecutive_statements = 0
+    end
+  end
+end

lib/theme_check/checks/unused_snippets.rb

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+require "set"
+
+module ThemeCheck
+  class UnusedSnippets < Check
+    severity :suggestion
+
+    def initialize
+      @used_templates = Set.new
+    end
+
+    def on_include(node)
+      if node.value.template_name_expr.is_a?(String)
+        @used_templates << "snippets/#{node.value.template_name_expr}.liquid"
+      else
+        # Can't reliably track unused snippets if an expression is used, ignore this check
+        @used_templates.clear
+        ignore!
+      end
+    end
+    alias_method :on_render, :on_include
+
+    def on_end
+      (theme.snippets - @used_templates.to_a).each do |template|
+        add_offense("This template is not used", template: template)
+      end
+    end
+  end
+end

lib/theme_check/node.rb

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+require 'active_support/core_ext/string/inflections'
+
+module ThemeCheck
+  class Node
+    attr_reader :value, :parent, :template
+
+    def initialize(value, parent, template)
+      raise ArgumentError, "Expected a Liquid AST Node" if value.is_a?(Node)
+      @value = value
+      @parent = parent
+      @template = template
+    end
+
+    def children
+      @children ||= begin
+        nodes =
+          if defined?(@value.class::ParseTreeVisitor)
+            @value.class::ParseTreeVisitor.new(@value, {}).children
+          elsif @value.respond_to?(:nodelist)
+            Array(@value.nodelist)
+          else
+            []
+          end
+        nodes.map { |node| Node.new(node, self, @template) }
+      end
+    end
+
+    def literal?
+      @value.is_a?(String) || @value.is_a?(Integer)
+    end
+
+    def tag?
+      @value.is_a?(Liquid::Tag)
+    end
+
+    def comment?
+      @value.is_a?(Liquid::Comment)
+    end
+
+    def document?
+      @value.is_a?(Liquid::Document)
+    end
+    alias_method :root?, :document?
+
+    def block_tag?
+      @value.is_a?(Liquid::Block)
+    end
+
+    def block?
+      block_tag? || block_body? || document?
+    end
+
+    def block_body?
+      @value.is_a?(Liquid::BlockBody)
+    end
+
+    def line_number
+      @value.line_number if @value.respond_to?(:line_number)
+    end
+
+    def type_name
+      @type_name ||= @value.class.name.demodulize.underscore.to_sym
+    end
+  end
+end

lib/theme_check/offense.rb

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+module ThemeCheck
+  class Offense < Struct.new(:check, :template, :node, :message)
+    def line_number
+      node&.line_number
+    end
+
+    def severity
+      check.severity
+    end
+
+    def doc
+      check.doc
+    end
+
+    def to_s
+      out = +''
+      out << "#{message} at #{template}"
+      out << ":#{line_number}" if line_number
+      out
+    end
+  end
+end