Increase perf on large codebases - Fix MadLittleMods#15 - v0.4.0

Author: MadLittleMods

CHANGELOG.md

@@ -1,4 +1,12 @@
 
+# v0.4.0 - 2015-7-2
+
+ - Fix #15
+ 	 - Remove slowness from cloning the `root` with `node.clone().removeAll()`. Now using `./lib/shallow-clone-node.js` to avoid cloning children which will get removed right after.
+ 	 - Thank you to @ddprrt for bringing up the slowness issue in this article, [PostCSS misconceptions](https://medium.com/@ddprrt/postcss-misconceptions-faf5dc5038df).
+
+
+
 # v0.3.9 - 2015-6-29
 
  - Remove `opts` global leak. Fix #13

README.md

@@ -8,7 +8,7 @@ CSS variables or CSS Custom Properties limited subset polyfill/shim.
 
 We strive for the most complete transformation but we/no plugin can achieve true complete parity according to the [specification](http://dev.w3.org/csswg/css-variables/) because of the DOM cascade unknowns.
 
-## Latest Version: v0.3.9
+## Latest Version: v0.4.0
 ### [Changelog](https://github.com/MadLittleMods/postcss-css-variables/blob/master/CHANGELOG.md)
 
 ### Install
@@ -236,6 +236,7 @@ The main features that we`postcss-css-variables` add/provide are:
  	 - Proper value substitution based on explicit DOM/structure traversal
  - At-rule support `@media`, `@support`, etc
  - Nested rules which can be fully deduced with [`postcss-nested`](https://github.com/postcss/postcss-nested).
+ - Pseudo class/element support `:hover`, etc
 
 
 

index.js

@@ -1,5 +1,5 @@
 // PostCSS CSS Variables (postcss-css-variables)
-// v0.3.8
+// v0.4.0
 //
 // https://github.com/MadLittleMods/postcss-css-variables
 
@@ -9,6 +9,7 @@
 var postcss = require('postcss');
 var extend = require('extend');
 
+var shallowCloneNode = require('./lib/shallow-clone-node');
 var resolveValue = require('./lib/resolve-value');
 var resolveDecl = require('./lib/resolve-decl');
 
@@ -23,7 +24,7 @@ var RE_VAR_PROP = (/(--(.+))/);
 
 function eachCssVariableDeclaration(css, cb) {
 	// Loop through all of the declarations and grab the variables and put them in the map
-	css.eachDecl(function(decl, index) {
+	css.eachDecl(function(decl) {
 		// If declaration is a variable
 		if(RE_VAR_PROP.test(decl.prop)) {
 			cb(decl);
@@ -137,7 +138,7 @@ module.exports = postcss.plugin('postcss-css-variables', function(options) {
 			// Split out each selector piece into its own declaration for easier logic down the road
 			decl.parent.selectors.forEach(function(selector) {
 				// Create a detached clone
-				var splitOutRule = decl.parent.clone().removeAll();
+				var splitOutRule = shallowCloneNode(decl.parent);
 				splitOutRule.selector = selector;
 				splitOutRule.parent = decl.parent.parent;
 

lib/clone-splice-parent-onto-node-when.js

@@ -1,3 +1,6 @@
+
+var shallowCloneNode = require('./shallow-clone-node');
+
 // Splice on a parent scope onto a node
 // And return a detached clone
 var cloneSpliceParentOntoNodeWhen = function(node, parent, /*optional*/whenCb) {
@@ -15,7 +18,7 @@ var cloneSpliceParentOntoNodeWhen = function(node, parent, /*optional*/whenCb) {
 			cloneList.push(current.clone());
 		}
 		else {
-			cloneList.push(current.clone().removeAll());
+			cloneList.push(shallowCloneNode(current));
 		}
 
 		isWhenNow = whenCb(current);
@@ -28,7 +31,7 @@ var cloneSpliceParentOntoNodeWhen = function(node, parent, /*optional*/whenCb) {
 	var cloneParentList = [];
 	var currentParent = parent;
 	while(currentParent) {
-		cloneParentList.push(currentParent.clone().removeAll());
+		cloneParentList.push(shallowCloneNode(currentParent));
 
 		currentParent = currentParent.parent;
 	}

lib/resolve-decl.js

@@ -5,6 +5,7 @@ var gatherVariableDependencies = require('./gather-variable-dependencies');
 var isUnderScope = require('./is-under-scope');
 var isNodeUnderScope = require('./is-node-under-scope');
 
+var shallowCloneNode = require('./shallow-clone-node');
 var findNodeAncestorWithSelector = require('./find-node-ancestor-with-selector');
 var cloneSpliceParentOntoNodeWhen = require('./clone-splice-parent-onto-node-when');
 
@@ -43,7 +44,7 @@ function eachMapItemDependencyOfDecl(variablesUsedList, map, decl, cb) {
 			// TODO: use regex from `isUnderScope`
 			else if(isUnderScope.RE_PSEUDO_SELECTOR.test(mapItem.parent.selector)) {
 				// Create a detached clone
-				var ruleClone = decl.parent.clone().removeAll();
+				var ruleClone = shallowCloneNode(decl.parent);
 				ruleClone.parent = decl.parent.parent;
 
 				// Add the declaration to it
@@ -91,7 +92,7 @@ function resolveDecl(decl, map, /*optional*/shouldPreserve, /*optional*/logResol
 	// Resolve the cascade dependencies
 	// Now find any at-rule declarations that need to be added below each rule
 	eachMapItemDependencyOfDecl(valueResults.variablesUsed, map, decl, function(mimicDecl, mapItem) {
-		var ruleClone = decl.parent.clone().removeAll();
+		var ruleClone = shallowCloneNode(decl.parent);
 		var declClone = decl.clone();
 		// No mangle resolve
 		declClone.value = _logResolveValueResult(resolveValue(mimicDecl, map, true)).value;
@@ -102,7 +103,7 @@ function resolveDecl(decl, map, /*optional*/shouldPreserve, /*optional*/logResol
 
 		if(mapItem.isUnderAtRule) {
 			// Create the clean atRule for which we place the declaration under
-			var atRuleNode = mapItem.parent.parent.clone().removeAll();
+			var atRuleNode = shallowCloneNode(mapItem.parent.parent);
 
 			// Add the rule to the atRule
 			atRuleNode.append(ruleClone);
@@ -113,7 +114,7 @@ function resolveDecl(decl, map, /*optional*/shouldPreserve, /*optional*/logResol
 			var currentAtRuleNode = mapItem.parent.parent;
 			while(currentAtRuleNode.parent.type === 'atrule') {
 				// Create a new clean clone of that at rule to nest under
-				var newParentAtRuleNode = currentAtRuleNode.parent.clone().removeAll();
+				var newParentAtRuleNode = shallowCloneNode(currentAtRuleNode.parent);
 
 				// Append the old parent
 				newParentAtRuleNode.append(parentAtRuleNode);

lib/shallow-clone-node.js

@@ -0,0 +1,46 @@
+// Inspired by the PostCSS clone: https://github.com/postcss/postcss/blob/caba908d0f4e362466252202e6be84660c33d8a5/lib/node.js#L17
+var shallowCloneNode = function(obj, parent) {
+	var cloned = new obj.constructor();
+
+	Object.keys(obj).forEach(function(i) {
+		if (!obj.hasOwnProperty(i)) {
+			return;
+		}
+
+		var value = obj[i];
+		var type = typeof value;
+
+		if (i === 'parent' && type === 'object') {
+			if (parent) {
+				cloned[i] = parent;
+			}
+		}
+		else if(i === 'source') {
+			cloned[i] = value;
+		}
+		else if (value instanceof Array) {
+			if(i === 'nodes') {
+				cloned[i] = [];
+			}
+			else {
+				cloned[i] = value.map(function(j) {
+					shallowCloneNode(j, cloned);
+				});
+			}
+		}
+		else if (
+			i !== 'before' && i !== 'after' &&
+			i !== 'between' && i !== 'semicolon'
+		) {
+			if(type === 'object') {
+				value = shallowCloneNode(value);
+			}
+
+			cloned[i] = value;
+		}
+	});
+
+	return cloned;
+};
+
+module.exports = shallowCloneNode;

package.json

@@ -1,6 +1,6 @@
 {
   "name": "postcss-css-variables",
-  "version": "0.3.9",
+  "version": "0.4.0",
   "description": "PostCSS plugin to transform CSS Custom Properties(CSS variables) syntax into a static representation",
   "keywords": [
     "postcss",

test/test.js

@@ -6,7 +6,7 @@ chai.use(chaiAsPromised);
 var postcss = require('postcss');
 
 var Promise = require('bluebird');
-var fs = Promise.promisifyAll(require("fs"));
+var fs = Promise.promisifyAll(require('fs'));
 var CleanCSS = require('clean-css');
 
 var cssvariables = require('../');