From e6d02dbd28ed87def5b391d1e5a686fd75570b85 Mon Sep 17 00:00:00 2001
From: Kevin Newton <kddnewton@gmail.com>
Date: Fri, 28 Jun 2024 10:11:54 -0400
Subject: [PATCH] Split up combinators logic

---
 Gemfile.lock                        |   1 +
 lib/syntax_tree/css/format.rb       | 110 +++++++++++---------
 lib/syntax_tree/css/pretty_print.rb | 150 +++++++++++++++++-----------
 lib/syntax_tree/css/selectors.rb    | 118 +++++++++++++++-------
 lib/syntax_tree/css/visitor.rb      |  16 ++-
 test/selectors_test.rb              |   9 +-
 6 files changed, 260 insertions(+), 144 deletions(-)

diff --git a/Gemfile.lock b/Gemfile.lock
index b027863..90a520b 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -22,6 +22,7 @@ GEM
       prettier_print (>= 1.2.0)
 
 PLATFORMS
+  arm64-darwin-23
   x86_64-darwin-21
   x86_64-linux
 
diff --git a/lib/syntax_tree/css/format.rb b/lib/syntax_tree/css/format.rb
index 3eb2a18..02e5059 100644
--- a/lib/syntax_tree/css/format.rb
+++ b/lib/syntax_tree/css/format.rb
@@ -42,13 +42,13 @@ def visit_delim_token(node)
         q.text(node.value)
       end
 
-      # Visit an IdentToken node.
-      def visit_ident_token(node)
+      # Visit a HashToken node.
+      def visit_hash_token(node)
         q.text(node.value)
       end
 
-      # Visit a HashToken node.
-      def visit_hash_token(node)
+      # Visit an IdentToken node.
+      def visit_ident_token(node)
         q.text(node.value)
       end
 
@@ -70,28 +70,79 @@ def visit_style_rule(node)
         end
       end
 
+      # Visit a Selectors::SubsequentSiblingCombinator node.
+      def visit_subsequent_sibling_combinator(node)
+        q.text(" ")
+        node.value.format(q)
+        q.text(" ")
+      end
+
       #-------------------------------------------------------------------------
       # Selector nodes
       #-------------------------------------------------------------------------
 
-      # Visit a Selectors::TypeSelector node.
-      def visit_type_selector(node)
+      # Visit a Selectors::ChildCombinator node.
+      def visit_child_combinator(node)
+        q.text(" ")
+        node.value.format(q)
+        q.text(" ")
+      end
+
+      # Visit a Selectors::ClassSelector node.
+      def visit_class_selector(node)
+        q.text(".")
+        node.value.format(q)
+      end
+
+      # Visit a Selectors::ColumnSiblingCombinator node.
+      def visit_column_sibling_combinator(node)
+        q.text(" ")
+        node.value.each { |value| value.format(q) }
+        q.text(" ")
+      end
+
+      # Visit a Selectors::ComplexSelector node.
+      def visit_complex_selector(node)
         q.group do
-          node.prefix.format(q) if node.prefix
-          node.value.format(q)
+          node.child_nodes.each do |child_node|
+            child_node.format(q)
+          end
+        end
+      end
+
+      # Visit a Selectors::CompoundSelector node.
+      def visit_compound_selector(node)
+        q.group do
+          node.child_nodes.each do |child_node|
+            child_node.format(q)
+          end
         end
       end
 
+      # Visit a Selectors::DescendantCombinator node.
+      def visit_descendant_combinator(node)
+        q.text(" ")
+      end
+
       # Visit a Selectors::IdSelector node.
       def visit_id_selector(node)
         q.text("#")
         node.value.format(q)
       end
 
-      # Visit a Selectors::ClassSelector node.
-      def visit_class_selector(node)
-        q.text(".")
+      # Visit a Selectors::NextSiblingCombinator node.
+      def visit_next_sibling_combinator(node)
+        q.text(" ")
         node.value.format(q)
+        q.text(" ")
+      end
+
+      # Visit a Selectors::TypeSelector node.
+      def visit_type_selector(node)
+        q.group do
+          node.prefix&.format(q)
+          node.value.format(q)
+        end
       end
 
       # Visit a Selectors::PseudoClassSelector node.
@@ -116,42 +167,9 @@ def visit_pseudo_element_selector(node)
         node.value.format(q)
       end
 
-      # Visit a Selectors::Combinator node.
-      def visit_combinator(node)
-        case node.value
-        when WhitespaceToken
-          q.text(" ")
-        when Array
-          q.text(" ")
-          node.value.each { |val| val.format(q) }
-          q.text(" ")
-        else
-          q.text(" ")
-          node.value.format(q)
-          q.text(" ")
-        end
-      end
-
-      # Visit a Selectors::ComplexSelector node.
-      def visit_complex_selector(node)
-        q.group do
-          node.child_nodes.each_with_index do |child_node, j|
-            child_node.format(q)
-          end
-        end
-      end
-
-      # Visit a Selectors::CompoundSelector node.
-      def visit_compound_selector(node)
-        q.group do
-          node.child_nodes.each do |node_|
-            node_.format(q)
-          end
-        end
-      end
-
+      # Visit a Selectors::WqName node.
       def visit_wqname(node)
-        node.prefix.format(q) if node.prefix
+        node.prefix&.format(q)
         node.name.format(q)
       end
     end
diff --git a/lib/syntax_tree/css/pretty_print.rb b/lib/syntax_tree/css/pretty_print.rb
index d5d93e3..8e10a1a 100644
--- a/lib/syntax_tree/css/pretty_print.rb
+++ b/lib/syntax_tree/css/pretty_print.rb
@@ -350,6 +350,73 @@ def visit_whitespace_token(node)
       # Selector nodes
       #-------------------------------------------------------------------------
 
+      # Visit a Selectors::ChildCombinator node.
+      def visit_child_combinator(node)
+        token("child-combinator") do
+          q.breakable
+          q.pp(node.value)
+        end
+      end
+
+      # Visit a Selectors::ColumnSiblingCombinator node.
+      def visit_column_sibling_combinator(node)
+        token("column-sibling-combinator") do
+          q.breakable
+          q.pp(node.value)
+        end
+      end
+
+      # Visit a Selectors::ComplexSelector node.
+      def visit_complex_selector(node)
+        token("complex-selector") do
+          node.child_nodes.each do |child|
+            q.breakable
+            q.pp(child)
+          end
+        end
+      end
+
+      # Visit a Selectors::CompoundSelector node.
+      def visit_compound_selector(node)
+        token("compound-selector") do
+          q.breakable
+          token("type") do
+            q.breakable
+            q.pp(node.type)
+          end
+
+          q.breakable
+          q.text("(subclasses")
+
+          if node.subclasses.any?
+            q.nest(2) do
+              q.breakable
+              q.seplist(node.subclasses) { |subclass| q.pp(subclass) }
+            end
+
+            q.breakable("")
+          end
+
+          q.text(")")
+
+          q.breakable("")
+          q.text("(pseudo-elements")
+
+          if node.pseudo_elements.any?
+            q.nest(2) do
+              q.breakable
+              q.seplist(node.pseudo_elements) do |pseudo_element|
+                q.pp(pseudo_element)
+              end
+            end
+
+            q.breakable("")
+          end
+
+          q.text(")")
+        end
+      end
+
       # Visit a Selectors::ClassSelector node.
       def visit_class_selector(node)
         token("class-selector") do
@@ -358,6 +425,14 @@ def visit_class_selector(node)
         end
       end
 
+      # Visit a Selectors::DescendantCombinator node.
+      def visit_descendant_combinator(node)
+        token("descendant-combinator") do
+          q.breakable
+          q.pp(node.value)
+        end
+      end
+
       # Visit a Selectors::IdSelector node.
       def visit_id_selector(node)
         token("id-selector") do
@@ -366,6 +441,14 @@ def visit_id_selector(node)
         end
       end
 
+      # Visit a Selectors::NextSiblingCombinator node.
+      def visit_next_sibling_combinator(node)
+        token("next-sibling-combinator") do
+          q.breakable
+          q.pp(node.value)
+        end
+      end
+
       # Visit a Selectors::PseudoClassSelector node.
       def visit_pseudo_class_selector(node)
         token("pseudo-class-selector") do
@@ -404,6 +487,14 @@ def visit_pseudo_element_selector(node)
         end
       end
 
+      # Visit a Selectors::SubsequentSiblingCombinator node.
+      def visit_subsequent_sibling_combinator(node)
+        token("subsequent-sibling-combinator") do
+          q.breakable
+          q.pp(node.value)
+        end
+      end
+
       # Visit a Selectors::TypeSelector node.
       def visit_type_selector(node)
         token("type-selector") do
@@ -430,65 +521,6 @@ def visit_wqname(node)
         end
       end
 
-      # Visit a Selectors::Combinator node.
-      def visit_combinator(node)
-        token(node.class::PP_NAME) do
-          q.breakable
-          q.pp(node.value)
-        end
-      end
-
-      # Visit a Selectors::ComplexSelector node.
-      def visit_complex_selector(node)
-        token("complex-selector") do
-          node.child_nodes.each do |child|
-            q.breakable
-            q.pp(child)
-          end
-        end
-      end
-
-      # Visit a Selectors::CompoundSelector node.
-      def visit_compound_selector(node)
-        token("compound-selector") do
-          q.breakable
-          token("type") do
-            q.breakable
-            q.pp(node.type)
-          end
-
-          q.breakable
-          q.text("(subclasses")
-
-          if node.subclasses.any?
-            q.nest(2) do
-              q.breakable
-              q.seplist(node.subclasses) { |subclass| q.pp(subclass) }
-            end
-
-            q.breakable("")
-          end
-
-          q.text(")")
-
-          q.breakable("")
-          q.text("(pseudo-elements")
-
-          if node.pseudo_elements.any?
-            q.nest(2) do
-              q.breakable
-              q.seplist(node.pseudo_elements) do |pseudo_element|
-                q.pp(pseudo_element)
-              end
-            end
-
-            q.breakable("")
-          end
-
-          q.text(")")
-        end
-      end
-
       private
 
       def token(name)
diff --git a/lib/syntax_tree/css/selectors.rb b/lib/syntax_tree/css/selectors.rb
index f15df10..84e8f51 100644
--- a/lib/syntax_tree/css/selectors.rb
+++ b/lib/syntax_tree/css/selectors.rb
@@ -71,6 +71,8 @@ def deconstruct_keys(keys)
         end
       end
 
+      # A joiner between two selectors.
+      # https://www.w3.org/TR/selectors-4/#combinators
       class Combinator < Node
         attr_reader :value
 
@@ -79,7 +81,7 @@ def initialize(value:)
         end
 
         def accept(visitor)
-          visitor.visit_combinator(self)
+          raise NoMethodError, __method__
         end
 
         def child_nodes
@@ -91,36 +93,65 @@ def child_nodes
         def deconstruct_keys(keys)
           { value: value }
         end
+
+        def type
+          raise NoMethodError, __method__
+        end
       end
 
       # §15.1 https://www.w3.org/TR/selectors-4/#descendant-combinators
       class DescendantCombinator < Combinator
-        TOKEN = WhitespaceToken
-        PP_NAME = "descendant-combinator"
+        def accept(visitor)
+          visitor.visit_descendant_combinator(self)
+        end
+
+        def type
+          "descendant-combinator"
+        end
       end
 
       # §15.2 https://www.w3.org/TR/selectors-4/#child-combinators
       class ChildCombinator < Combinator
-        TOKEN = ">"
-        PP_NAME = "child-combinator"
+        def accept(visitor)
+          visitor.visit_child_combinator(self)
+        end
+
+        def type
+          "child-combinator"
+        end
       end
 
       # §15.3 https://www.w3.org/TR/selectors-4/#adjacent-sibling-combinators
       class NextSiblingCombinator < Combinator
-        TOKEN = "+"
-        PP_NAME = "next-sibling-combinator"
+        def accept(visitor)
+          visitor.visit_next_sibling_combinator(self)
+        end
+
+        def type
+          "next-sibling-combinator"
+        end
       end
 
       # §15.4 https://www.w3.org/TR/selectors-4/#general-sibling-combinators
       class SubsequentSiblingCombinator < Combinator
-        TOKEN = "~"
-        PP_NAME = "subsequent-sibling-combinator"
+        def accept(visitor)
+          visitor.visit_subsequent_sibling_combinator(self)
+        end
+
+        def type
+          "subsequent-sibling-combinator"
+        end
       end
 
       # §16.1 https://www.w3.org/TR/selectors-4/#the-column-combinator
       class ColumnSiblingCombinator < Combinator
-        TOKEN = ["|", "|"]
-        PP_NAME = "column-sibling-combinator"
+        def accept(visitor)
+          visitor.visit_column_sibling_combinator(self)
+        end
+
+        def type
+          "column-sibling-combinator"
+        end
       end
 
       class ComplexSelector < Node
@@ -430,11 +461,11 @@ def simple_selector
       # <combinator> = '>' | '+' | '~' | [ '|' '|' ]
       def combinator
         options do
-          maybe { consume_combinator(ChildCombinator) } ||
-            maybe { consume_combinator(NextSiblingCombinator) } ||
-            maybe { consume_combinator(SubsequentSiblingCombinator) } ||
-            maybe { consume_combinator(ColumnSiblingCombinator) } ||
-            maybe { consume_combinator(DescendantCombinator) }
+          maybe { consume_child_combinator } ||
+            maybe { consume_next_sibling_combinator } ||
+            maybe { consume_subsequent_sibling_combinator } ||
+            maybe { consume_column_sibling_combinator } ||
+            maybe { consume_descendant_combinator }
         end
       end
 
@@ -579,30 +610,47 @@ def one_or_more
         end
       end
 
-      def consume_combinator(combinator_class)
-        eat_whitespace = (combinator_class::TOKEN != WhitespaceToken)
+      def consume_child_combinator
+        consume_whitespace
+        result = consume(">")
+        consume_whitespace
+        ChildCombinator.new(value: result)
+      end
+
+      def consume_next_sibling_combinator
+        consume_whitespace
+        result = consume("+")
+        consume_whitespace
+        NextSiblingCombinator.new(value: result)
+      end
 
-        consume_whitespace if eat_whitespace
-        result = consume(*combinator_class::TOKEN)
-        consume_whitespace if eat_whitespace
+      def consume_subsequent_sibling_combinator
+        consume_whitespace
+        result = consume("~")
+        consume_whitespace
+        SubsequentSiblingCombinator.new(value: result)
+      end
 
-        combinator_class.new(value: result)
+      def consume_column_sibling_combinator
+        consume_whitespace
+        result = [consume("|"), consume("|")]
+        consume_whitespace
+        ColumnSiblingCombinator.new(value: result)
       end
 
-      def consume(*values)
-        result =
-          values.map do |value|
-            case [value, tokens.peek]
-            in [String, DelimToken[value: token_value]] if value == token_value
-              tokens.next
-            in [Class, token] if token.is_a?(value)
-              tokens.next
-            in [_, token]
-              raise MissingTokenError, "Expected #{value} but got #{token.inspect}"
-            end
-          end
+      def consume_descendant_combinator
+        DescendantCombinator.new(value: consume(WhitespaceToken))
+      end
 
-        result.size == 1 ? result.first : result
+      def consume(value)
+        case [value, tokens.peek]
+        in [String, DelimToken[value: token_value]] if value == token_value
+          tokens.next
+        in [Class, token] if token.is_a?(value)
+          tokens.next
+        in [_, token]
+          raise MissingTokenError, "Expected #{value} but got #{token.inspect}"
+        end
       end
 
       def maybe
diff --git a/lib/syntax_tree/css/visitor.rb b/lib/syntax_tree/css/visitor.rb
index 79ca353..6a3599d 100644
--- a/lib/syntax_tree/css/visitor.rb
+++ b/lib/syntax_tree/css/visitor.rb
@@ -129,11 +129,14 @@ def visit_child_nodes(node)
       # Selector nodes
       #-------------------------------------------------------------------------
 
+      # Visit a Selectors::ChildCombinator node.
+      alias visit_child_combinator visit_child_nodes
+
       # Visit a Selectors::ClassSelector node.
       alias visit_class_selector visit_child_nodes
 
-      # Visit a Selectors::Combinator node.
-      alias visit_combinator visit_child_nodes
+      # Visit a Selectors::ColumnSiblingCombinator node.
+      alias visit_column_sibling_combinator visit_child_nodes
 
       # Visit a Selectors::ComplexSelector node.
       alias visit_complex_selector visit_child_nodes
@@ -141,9 +144,15 @@ def visit_child_nodes(node)
       # Visit a Selectors::CompoundSelector node.
       alias visit_compound_selector visit_child_nodes
 
+      # Visit a Selectors::DescendantCombinator node.
+      alias visit_descendant_combinator visit_child_nodes
+
       # Visit a Selectors::IdSelector node.
       alias visit_id_selector visit_child_nodes
 
+      # Visit a Selectors::NextSiblingCombinator node.
+      alias visit_next_sibling_combinator visit_child_nodes
+
       # Visit a Selectors::PseudoClassFunction node.
       alias visit_pseudo_class_function visit_child_nodes
 
@@ -153,6 +162,9 @@ def visit_child_nodes(node)
       # Visit a Selectors::PseudoElementSelector node.
       alias visit_pseudo_element_selector visit_child_nodes
 
+      # Visit a Selectors::SubsequentSiblingCombinator node.
+      alias visit_subsequent_sibling_combinator visit_child_nodes
+
       # Visit a Selectors::TypeSelector node.
       alias visit_type_selector visit_child_nodes
 
diff --git a/test/selectors_test.rb b/test/selectors_test.rb
index 659d061..3c99a50 100644
--- a/test/selectors_test.rb
+++ b/test/selectors_test.rb
@@ -317,8 +317,13 @@ def assert_selector_format(selectors, expected)
       private
 
       def parse_selectors(selectors)
-        css = selectors + " {}"
-        Parser.new(css).parse.rules.first.selectors
+        rule = Parser.new("#{selectors} {}").parse.rules.first
+
+        # Pretty-print and format so that we have coverage.
+        PP.pp(rule, +"")
+        PrettierPrint.format(+"", 80) { |q| rule.format(q) }
+
+        rule.selectors
       end
     end
   end