Option to remove empty rulesets. Closes #67.

Author: anton-rudeshko

.csscomb.json

@@ -12,6 +12,7 @@
     "element-case": "lower",
     "eof-newline": true,
     "leading-zero": false,
+    "remove-empty-rulesets": true,
     "rule-indent": true,
     "stick-brace": "\n",
     "strip-spaces": true,

README.md

@@ -42,6 +42,7 @@ Example configuration:
     "exclude": ["node_modules/**"],
     "verbose": true,
 
+    "remove-empty-rulesets": true,
     "always-semicolon": true,
     "block-indent": true,
     "colon-space": true,
@@ -88,6 +89,14 @@ $ ./bin/csscomb ./test --verbose
 $ ./bin/csscomb ./test -v
 ```
 
+### remove-empty-rulesets
+
+Available values: `{Boolean}` `true`
+
+Example: `{ "remove-empty-rulesets": true }` - remove rulesets that have no declarations or comments.
+
+`a { color: red; } p { /* hey */ } b { }` → `a { color: red; } p { /* hey */ } `
+
 ### always-semicolon
 
 Available value: `{Boolean}` `true`

lib/csscomb.js

@@ -11,6 +11,7 @@ var vfs = require('vow-fs');
  */
 var Comb = function() {
     this._options = [
+        'remove-empty-rulesets',
         'always-semicolon',
         'color-case',
         'color-shorthand',

lib/options/remove-empty-rulesets.js

@@ -0,0 +1,85 @@
+module.exports = {
+
+    /**
+     * Sets handler value.
+     *
+     * @param {String} value Option value
+     * @returns {Object|undefined}
+     */
+    setValue: function(value) {
+        if (value === true) {
+            this._value = value;
+            return this;
+        }
+    },
+
+    /**
+     * Remove rulesets with no declarations.
+     *
+     * @param {String} nodeType
+     * @param {Array} nodeContent
+     */
+    process: function(nodeType, nodeContent) {
+        if (nodeType === 'stylesheet') {
+            this._processStylesheetContent(nodeContent);
+        }
+    },
+
+    _processStylesheetContent: function(nodeContent) {
+        this._removeEmptyRulesets(nodeContent);
+        this._mergeAdjacentWhitespace(nodeContent);
+    },
+
+    _removeEmptyRulesets: function(nodeContent) {
+        var i = nodeContent.length;
+        while (i--) {
+            if (this._isRuleset(nodeContent[i]) && this._isEmptyRuleset(nodeContent[i])) {
+                nodeContent.splice(i, 1);
+            }
+        }
+    },
+
+    /**
+     * Removing ruleset nodes from tree may result in two adjacent whitespace nodes which is not correct AST:
+     * [space, ruleset, space] => [space, space]
+     * To ensure correctness of further processing we should merge such nodes into one.
+     * [space, space] => [space]
+     */
+    _mergeAdjacentWhitespace: function(nodeContent) {
+        var i = nodeContent.length - 1;
+        while (i-- > 0) {
+            if (this._isWhitespace(nodeContent[i]) && this._isWhitespace(nodeContent[i + 1])) {
+                nodeContent[i][1] += nodeContent[i + 1][1];
+                nodeContent.splice(i + 1, 1);
+            }
+        }
+    },
+
+    _isEmptyRuleset: function(ruleset) {
+        return ruleset.filter(this._isBlock).every(this._isEmptyBlock, this);
+    },
+
+    /**
+     * Block considered empty when it has no declarations or comments.
+     */
+    _isEmptyBlock: function(node) {
+        return !node.some(this._isDeclarationOrComment);
+    },
+
+    _isDeclarationOrComment: function(node) {
+        return node[0] === 'declaration' || node[0] === 'comment';
+    },
+
+    _isRuleset: function(node) {
+        return node[0] === 'ruleset';
+    },
+
+    _isBlock: function(node) {
+        return node[0] === 'block';
+    },
+
+    _isWhitespace: function(node) {
+        return node[0] === 's';
+    }
+
+};

test/integral.origin.css

@@ -80,7 +80,7 @@ a, b, i /* foobar */ {
     outline: 0;
     padding: 0.4em 0;
 }
-}
+}.empty-rule{}
 
 /* Фигурные скобки. Вариант 2 */
 div
@@ -120,7 +120,7 @@ top: 0;/* ololo */margin :0;}
     b
         {
 top :0/* trololo */;margin : 0}
-
+.empty-rule{}
 
 
 

test/remove-empty-rulesets.js

@@ -0,0 +1,99 @@
+var Comb = require('../lib/csscomb');
+var assert = require('assert');
+
+describe('options/remove-empty-rulesets', function() {
+    var comb;
+
+    beforeEach(function() {
+        comb = new Comb();
+    });
+
+    describe('configured with invalid value', function() {
+        beforeEach(function() {
+            comb.configure({ 'remove-empty-rulesets': 'foobar' });
+        });
+
+        it('should not remove empty ruleset', function() {
+            assert.equal(comb.processString('a { width: 10px; } b {}'), 'a { width: 10px; } b {}');
+        });
+    });
+
+    describe('configured with Boolean "true" value', function() {
+        beforeEach(function() {
+            comb.configure({ 'remove-empty-rulesets': true });
+        });
+
+        it('should remove empty ruleset', function() {
+            assert.equal(comb.processString(' b {} '), '  ');
+        });
+
+        it('should leave ruleset with declarations', function() {
+            assert.equal(comb.processString('a { width: 10px; }\nb {} '), 'a { width: 10px; }\n ');
+        });
+
+        it('should leave ruleset with comments', function() {
+            assert.equal(comb.processString('a { /* comment */ }\nb {} '), 'a { /* comment */ }\n ');
+        });
+    });
+});
+
+describe('options/remove-empty-rulesets AST manipulation', function() {
+    var rule;
+    var nodeContent;
+
+    beforeEach(function() {
+        rule = require('../lib/options/remove-empty-rulesets.js');
+    });
+
+    describe('merge adjacent whitespace', function() {
+        it('should do nothing with empty content', function() {
+            nodeContent = [];
+            rule._mergeAdjacentWhitespace(nodeContent);
+            assert.deepEqual(nodeContent, []);
+        });
+
+        it('should do nothing with only one whitespace', function() {
+            nodeContent = [['s', '  ']];
+            rule._mergeAdjacentWhitespace(nodeContent);
+            assert.deepEqual(nodeContent, [['s', '  ']]);
+        });
+
+        it('should merge two adjacent whitespaces', function() {
+            nodeContent = [['s', '  '], ['s', ' \n']];
+            rule._mergeAdjacentWhitespace(nodeContent);
+            assert.deepEqual(nodeContent, [['s', '   \n']]);
+        });
+
+        it('should merge three adjacent whitespaces', function() {
+            nodeContent = [['s', '  '], ['s', ' \n'], ['s', ' \n']];
+            rule._mergeAdjacentWhitespace(nodeContent);
+            assert.deepEqual(nodeContent, [['s', '   \n \n']]);
+        });
+    });
+
+    describe('remove empty rulesets', function() {
+        it('should do nothing with empty content', function() {
+            nodeContent = [];
+            rule._removeEmptyRulesets(nodeContent);
+            assert.deepEqual(nodeContent, []);
+        });
+
+        it('should do nothing with no rulesets', function() {
+            nodeContent = [['s', '  ']];
+            rule._removeEmptyRulesets(nodeContent);
+            assert.deepEqual(nodeContent, [['s', '  ']]);
+        });
+
+        it('should remove empty ruleset', function() {
+            nodeContent = [['ruleset', []]];
+            rule._removeEmptyRulesets(nodeContent);
+            assert.deepEqual(nodeContent, []);
+        });
+
+        it('should remove two empty rulesets', function() {
+            nodeContent = [['s', '  '], ['ruleset', []], ['s', ' \n'], ['ruleset', []]];
+            rule._removeEmptyRulesets(nodeContent);
+            assert.deepEqual(nodeContent, [['s', '  '], ['s', ' \n']]);
+        });
+    });
+});