Add detection for root specifiers

Author: dqbd

index.js

@@ -12,6 +12,7 @@ var extend = require('extend');
 var shallowCloneNode = require('./lib/shallow-clone-node');
 var resolveValue = require('./lib/resolve-value');
 var resolveDecl = require('./lib/resolve-decl');
+var isPieceRootSpecificSelector = require('./lib/is-piece-root-specific-selector')
 
 
 // A custom property is any property whose name starts with two dashes (U+002D HYPHEN-MINUS)
@@ -179,7 +180,8 @@ module.exports = postcss.plugin('postcss-css-variables', function(options) {
 					variablesUsed: valueResults.variablesUsed,
 					parent: splitOutRule,
 					// variables inside root or at-rules (eg. @media, @support)
-					isUnderAtRule: splitOutRule.parent.type === 'atrule'
+					isUnderAtRule: splitOutRule.parent.type === 'atrule',
+					isRootSpecific: isPieceRootSpecificSelector(decl.parent.selector)
 				});
 			});
 

lib/is-piece-root-specific-selector.js

@@ -0,0 +1,20 @@
+const cssSelect = require('postcss-selector-parser')
+const isPieceAlwaysAncestorSelector = require('./is-piece-always-ancestor-selector')
+
+const isPieceRootSpecificSelector = (piece) => 
+  cssSelect((selectors) => {
+    let isRootOrHtml = false
+    let isSpecific = false
+    
+    selectors.walk((selector) => {
+      if (isPieceAlwaysAncestorSelector(selector.value)) {
+        isRootOrHtml = true
+      } else if (isRootOrHtml) {
+        isSpecific = true
+      }
+    })
+
+    return isSpecific
+  }).transformSync(piece)
+
+module.exports = isPieceRootSpecificSelector