Include an explicit Combinator in the AST for implicit descendant

lib/syntax_tree/css/format.rb

@@ -108,14 +108,24 @@ def visit_pseudo_element_selector(node)
 
       # Visit a Selectors::Combinator node.
       def visit_combinator(node)
-        node.value.format(q)
+        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|
-            q.text(" ") unless j == 0
             child_node.format(q)
           end
         end

lib/syntax_tree/css/pretty_print.rb

@@ -423,7 +423,7 @@ def visit_wqname(node)
 
       # Visit a Selectors::Combinator node.
       def visit_combinator(node)
-        token("combinator") do
+        token(node.class::PP_NAME) do
           q.breakable
           q.pp(node.value)
         end

lib/syntax_tree/css/selectors.rb

@@ -93,6 +93,36 @@ def deconstruct_keys(keys)
         end
       end
 
+      # §15.1 https://www.w3.org/TR/selectors-4/#descendant-combinators
+      class DescendantCombinator < Combinator
+        TOKEN = WhitespaceToken
+        PP_NAME = "descendant-combinator"
+      end
+
+      # §15.2 https://www.w3.org/TR/selectors-4/#child-combinators
+      class ChildCombinator < Combinator
+        TOKEN = ">"
+        PP_NAME = "child-combinator"
+      end
+
+      # §15.3 https://www.w3.org/TR/selectors-4/#adjacent-sibling-combinators
+      class NextSiblingCombinator < Combinator
+        TOKEN = "+"
+        PP_NAME = "next-sibling-combinator"
+      end
+
+      # §15.4 https://www.w3.org/TR/selectors-4/#general-sibling-combinators
+      class SubsequentSiblingCombinator < Combinator
+        TOKEN = "~"
+        PP_NAME = "subsequent-sibling-combinator"
+      end
+
+      # §16.1 https://www.w3.org/TR/selectors-4/#the-column-combinator
+      class ColumnSiblingCombinator < Combinator
+        TOKEN = ["|", "|"]
+        PP_NAME = "column-sibling-combinator"
+      end
+
       class ComplexSelector < Node
         attr_reader :child_nodes
 
@@ -333,12 +363,12 @@ def relative_selector_list
       def complex_selector
         child_nodes = [compound_selector]
 
+        combinator_ = nil
+        compound_selector_ = nil
         loop do
-          if (c = maybe { combinator })
-            child_nodes << c
-          end
-          if (s = maybe { compound_selector })
-            child_nodes << s
+          if maybe { (combinator_ = combinator) && (compound_selector_ = compound_selector) }
+            child_nodes << combinator_
+            child_nodes << compound_selector_
           else
             break
           end
@@ -363,8 +393,6 @@ def relative_selector
       # <compound-selector> = [ <type-selector>? <subclass-selector>*
       #   [ <pseudo-element-selector> <pseudo-class-selector>* ]* ]!
       def compound_selector
-        consume_whitespace
-
         type = maybe { type_selector }
         subclasses = []
 
@@ -401,17 +429,13 @@ def simple_selector
 
       # <combinator> = '>' | '+' | '~' | [ '|' '|' ]
       def combinator
-        consume_whitespace
-
-        value =
-          options do
-            maybe { consume(">") } ||
-              maybe { consume("+") } ||
-              maybe { consume("~") } ||
-              maybe { consume("|", "|") }
-          end
-
-        Combinator.new(value: value)
+        options do
+          maybe { consume_combinator(ChildCombinator) } ||
+            maybe { consume_combinator(NextSiblingCombinator) } ||
+            maybe { consume_combinator(SubsequentSiblingCombinator) } ||
+            maybe { consume_combinator(ColumnSiblingCombinator) } ||
+            maybe { consume_combinator(DescendantCombinator) }
+        end
       end
 
       # <type-selector> = <wq-name> | <ns-prefix>? '*'
@@ -554,6 +578,16 @@ def one_or_more
         end
       end
 
+      def consume_combinator(combinator_class)
+        eat_whitespace = (combinator_class::TOKEN != WhitespaceToken)
+
+        consume_whitespace if eat_whitespace
+        result = consume(*combinator_class::TOKEN)
+        consume_whitespace if eat_whitespace
+
+        combinator_class.new(value: result)
+      end
+
       def consume(*values)
         result =
           values.map do |value|

test/selectors_test.rb

@@ -128,15 +128,23 @@ class SelectorsTest < Minitest::Spec
         end
 
         it "parses a complex selector" do
-          actual = parse_selectors("section>table")
+          actual = parse_selectors("a b > c + d ~ e || f")
 
           assert_pattern do
             actual => [
               Selectors::ComplexSelector[
                 child_nodes: [
-                  Selectors::TypeSelector[value: { name: { value: "section" } }],
-                  Selectors::Combinator[value: { value: ">" }],
-                  Selectors::TypeSelector[value: { name: { value: "table" } }]
+                  Selectors::TypeSelector[value: { name: { value: "a" } }],
+                  Selectors::DescendantCombinator,
+                  Selectors::TypeSelector[value: { name: { value: "b" } }],
+                  Selectors::ChildCombinator,
+                  Selectors::TypeSelector[value: { name: { value: "c" } }],
+                  Selectors::NextSiblingCombinator,
+                  Selectors::TypeSelector[value: { name: { value: "d" } }],
+                  Selectors::SubsequentSiblingCombinator,
+                  Selectors::TypeSelector[value: { name: { value: "e" } }],
+                  Selectors::ColumnSiblingCombinator,
+                  Selectors::TypeSelector[value: { name: { value: "f" } }],
                 ]
               ]
             ]
@@ -185,6 +193,7 @@ class SelectorsTest < Minitest::Spec
               Selectors::ComplexSelector[
                 child_nodes: [
                   Selectors::TypeSelector[value: { name: { value: "section" } }],
+                  Selectors::Combinator[value: { value: " " }],
                   Selectors::TypeSelector[value: { name: { value: "table" } }],
                 ]
               ]
@@ -202,6 +211,7 @@ class SelectorsTest < Minitest::Spec
                   Selectors::TypeSelector[value: { name: { value: "section" } }],
                   Selectors::Combinator[value: { value: ">" }],
                   Selectors::TypeSelector[value: { name: { value: "table" } }],
+                  Selectors::Combinator[value: { value: " " }],
                   Selectors::TypeSelector[value: { name: { value: "tr" } }]
                 ]
               ]
@@ -249,6 +259,13 @@ class SelectorsTest < Minitest::Spec
               ".outer section.foo > table.bar tr",
             )
           end
+
+          it "handles all the combinators" do
+            assert_selector_format(
+              "a b > c + d ~ e || f",
+              "a b > c + d ~ e || f",
+            )
+          end
         end
 
         private