Include an explicit Combinator in the AST for implicit descendant

Making the descendant combinator explicit (where previously it was
implicit by having two CompoundSelectors next to each other in a
ComplexSelector) makes consuming the AST easier for visitors, and
simplifies the parser.

Author: flavorjones

lib/syntax_tree/css/format.rb

@@ -108,14 +108,20 @@ 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(" ")
+        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/selectors.rb

@@ -333,12 +333,12 @@ 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 +363,6 @@ 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 = []
 
@@ -401,14 +399,13 @@ def simple_selector
 
       # <combinator> = '>' | '+' | '~' | [ '|' '|' ]
       def combinator
-        consume_whitespace
-
         value =
           options do
-            maybe { consume(">") } ||
-              maybe { consume("+") } ||
-              maybe { consume("~") } ||
-              maybe { consume("|", "|") }
+            maybe { consume_combinator(">") } ||
+              maybe { consume_combinator("+") } ||
+              maybe { consume_combinator("~") } ||
+              maybe { consume_combinator("|", "|") } ||
+              maybe { consume(WhitespaceToken) }
           end
 
         Combinator.new(value: value)
@@ -554,6 +551,13 @@ def one_or_more
         end
       end
 
+      def consume_combinator(*values)
+        consume_whitespace
+        result = consume(*values)
+        consume_whitespace
+        result
+      end
+
       def consume(*values)
         result =
           values.map do |value|

test/selectors_test.rb

@@ -185,6 +185,7 @@ 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 +203,7 @@ 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" } }]
                 ]
               ]