Liquid::Traversal

This enables traversal over whole document tree.

lib/liquid/condition.rb

@@ -29,7 +29,7 @@ def self.operators
       @@operators
     end
 
-    attr_reader :attachment
+    attr_reader :attachment, :child_condition
     attr_accessor :left, :operator, :right
 
     def initialize(left = nil, operator = nil, right = nil)
@@ -83,7 +83,7 @@ def inspect
 
     protected
 
-    attr_reader :child_relation, :child_condition
+    attr_reader :child_relation
 
     private
 

lib/liquid/tags/assign.rb

@@ -10,6 +10,8 @@ module Liquid
   class Assign < Tag
     Syntax = /(#{VariableSignature}+)\s*=\s*(.*)\s*/om
 
+    attr_reader :to, :from
+
     def initialize(tag_name, markup, options)
       super
       if markup =~ Syntax

lib/liquid/tags/case.rb

@@ -3,6 +3,8 @@ class Case < Block
     Syntax     = /(#{QuotedFragment})/o
     WhenSyntax = /(#{QuotedFragment})(?:(?:\s+or\s+|\s*\,\s*)(#{QuotedFragment}.*))?/om
 
+    attr_reader :blocks, :left
+
     def initialize(tag_name, markup, options)
       super
       @blocks = []

lib/liquid/tags/cycle.rb

@@ -15,6 +15,8 @@ class Cycle < Tag
     SimpleSyntax = /\A#{QuotedFragment}+/o
     NamedSyntax  = /\A(#{QuotedFragment})\s*\:\s*(.*)/om
 
+    attr_reader :variables
+
     def initialize(tag_name, markup, options)
       super
       case markup

lib/liquid/tags/for.rb

@@ -46,8 +46,8 @@ module Liquid
   class For < Block
     Syntax = /\A(#{VariableSegment}+)\s+in\s+(#{QuotedFragment}+)\s*(reversed)?/o
 
-    attr_reader :collection_name
-    attr_reader :variable_name
+    attr_reader :collection_name, :variable_name, :limit, :from,
+      :for_block, :else_block
 
     def initialize(tag_name, markup, options)
       super

lib/liquid/tags/if.rb

@@ -14,21 +14,23 @@ class If < Block
     ExpressionsAndOperators = /(?:\b(?:\s?and\s?|\s?or\s?)\b|(?:\s*(?!\b(?:\s?and\s?|\s?or\s?)\b)(?:#{QuotedFragment}|\S+)\s*)+)/o
     BOOLEAN_OPERATORS = %w(and or)
 
+    attr_reader :blocks
+
     def initialize(tag_name, markup, options)
       super
       @blocks = []
       push_block('if'.freeze, markup)
     end
 
+    def nodelist
+      @blocks.map(&:attachment)
+    end
+
     def parse(tokens)
       while parse_body(@blocks.last.attachment, tokens)
       end
     end
 
-    def nodelist
-      @blocks.map(&:attachment)
-    end
-
     def unknown_tag(tag, markup, tokens)
       if ['elsif'.freeze, 'else'.freeze].include?(tag)
         push_block(tag, markup)

lib/liquid/tags/include.rb

@@ -16,6 +16,8 @@ module Liquid
   class Include < Tag
     Syntax = /(#{QuotedFragment}+)(\s+(?:with|for)\s+(#{QuotedFragment}+))?/o
 
+    attr_reader :template_name_expr, :variable_name_expr, :attributes
+
     def initialize(tag_name, markup, options)
       super
 

lib/liquid/tags/table_row.rb

@@ -2,6 +2,8 @@ module Liquid
   class TableRow < Block
     Syntax = /(\w+)\s+in\s+(#{QuotedFragment}+)/o
 
+    attr_reader :variable_name, :collection_name, :attributes
+
     def initialize(tag_name, markup, options)
       super
       if markup =~ Syntax

lib/liquid/traversal.rb

@@ -0,0 +1,120 @@
+# frozen_string_literal: true
+
+module Liquid
+  class Traversal
+    def self.for(node, callbacks = Hash.new(proc {}))
+      kase = CASES.find { |(klass, _)| node.is_a?(klass) }&.last
+      (kase || self).new(node, callbacks)
+    end
+
+    def initialize(node, callbacks)
+      @node = node
+      @callbacks = callbacks
+    end
+
+    def callback_for(*classes, &block)
+      cb = block
+      cb = ->(node, _) { block[node] } if block.arity.abs == 1
+      cb = ->(_, _) { block[] } if block.arity.zero?
+      classes.each { |klass| @callbacks[klass] = cb }
+      self
+    end
+
+    def traverse(context = nil)
+      children.map do |node|
+        item, new_context = @callbacks[node.class][node, context]
+        [
+          item,
+          Traversal.for(node, @callbacks).traverse(
+            new_context.nil? ? context : new_context
+          )
+        ]
+      end
+    end
+
+    protected
+
+    def children
+      @node.respond_to?(:nodelist) ? Array(@node.nodelist) : []
+    end
+
+    class Assign < Traversal
+      def children
+        [@node.from]
+      end
+    end
+
+    class Case < Traversal
+      def children
+        [@node.left] + @node.blocks
+      end
+    end
+
+    class Condition < Traversal
+      def children
+        [
+          @node.left, @node.right,
+          @node.child_condition, @node.attachment
+        ].compact
+      end
+    end
+
+    class Cycle < Traversal
+      def children
+        Array(@node.variables)
+      end
+    end
+
+    class For < Traversal
+      def children
+        (super + [@node.limit, @node.from, @node.collection_name]).compact
+      end
+    end
+
+    class If < Traversal
+      def children
+        @node.blocks
+      end
+    end
+
+    class Include < Traversal
+      def children
+        [
+          @node.template_name_expr,
+          @node.variable_name_expr
+        ] + @node.attributes.values
+      end
+    end
+
+    class TableRow < Traversal
+      def children
+        super + @node.attributes.values + [@node.collection_name]
+      end
+    end
+
+    class Variable < Traversal
+      def children
+        [@node.name] + @node.filters.flatten
+      end
+    end
+
+    class VariableLookup < Traversal
+      def children
+        @node.lookups
+      end
+    end
+
+    CASES = {
+      Liquid::Assign => Assign,
+      Liquid::Case => Case,
+      Liquid::Condition => Condition,
+      Liquid::Cycle => Cycle,
+      Liquid::For => For,
+      Liquid::If => If,
+      Liquid::Include => Include,
+      Liquid::TableRow => TableRow,
+      Liquid::Variable => Variable,
+      Liquid::VariableLookup => VariableLookup
+    }.freeze
+  end
+end