Implement sibling operators

Author: eush77

lib/select.js

@@ -12,24 +12,64 @@ select.ruleSet = function (selector, ast) {
 select.rule = function (selector, ast) {
   var result = [];
 
-  (function walk (node) {
+  switch (selector.nestingOperator) {
+    case null:
+    case undefined:
+    case '>':
+      walk(ast);
+      break;
+
+    case '+':
+      if (ast.children && ast.children.length) {
+        walk(ast.children[0], ast);
+      }
+      break;
+
+    case '~':
+      (ast.children || []).forEach(function (node) {
+        walk(node, ast);
+      });
+      break;
+
+    default:
+      throw Error('Unexpected nesting operator: ' + selector.nestingOperator);
+  }
+
+  return result;
+
+  function walk (node, parent) {
     if (node.type == selector.tagName) {
       if (!selector.rule) {
-        return result.push(node);
-      }
-      if (!node.children) {
-        return;
+        return append(result, [node]);
       }
 
-      node.children.forEach(function (childNode) {
-        [].push.apply(result, select.rule(selector.rule, childNode));
-      });
+      if (!selector.rule.nestingOperator || selector.rule.nestingOperator == '>') {
+        if (!node.children) return;
+        node.children.forEach(function (childNode) {
+          [].push.apply(result, select.rule(selector.rule, childNode));
+        });
+      }
+      else {
+        if (!parent) return;
+        append(result, select.rule(selector.rule, {
+          children: parent.children.slice(parent.children.indexOf(node) + 1)
+        }));
+      }
     }
 
     if (!selector.nestingOperator && node.children) {
-      node.children.forEach(walk);
+      node.children.forEach(function (child) {
+        walk(child, node);
+      });
     }
-  }(ast));
-
-  return result;
+  }
 };
+
+
+function append (array, elements) {
+  elements.forEach(function (el) {
+    if (array.indexOf(el) < 0) {
+      array.push(el);
+    }
+  });
+}

lib/selector.js

@@ -5,6 +5,6 @@ var Parser = require('css-selector-parser').CssSelectorParser;
 
 module.exports = function SelectorParser () {
   var parser = new Parser;
-  parser.registerNestingOperators('>');
+  parser.registerNestingOperators('>', '+', '~');
   return parser.parse.bind(parser);
 };

test/test.js

@@ -48,3 +48,18 @@ test('nesting', function (t) {
   ]);
   t.end();
 });
+
+
+test('siblings', function (t) {
+  t.deepEqual(select(ast, 'root ~ heading'), []);
+  t.deepEqual(select(ast, 'heading ~ heading'), [
+    path(ast, [1]),
+    path(ast, [7]),
+    path(ast, [12]),
+    path(ast, [16])
+  ]);
+  t.deepEqual(select(ast, 'heading + heading'), [
+    path(ast, [1])
+  ]);
+  t.end();
+});