disallowTrailingWhitespace: use CST for fix method

lib/rules/disallow-trailing-whitespace.js

@@ -85,11 +85,20 @@ module.exports.prototype = {
         var linebreak = file.getLineBreakStyle();
         var lines = file.getLines();
 
+        var stripTrailingWs = ignoreEmptyLines ?
+            function(line) {
+                return line.match(/^\s*$/) ? line : line.trimRight();
+            }
+            : Function.prototype.call.bind(String.prototype.trimRight);
+
         var fixed = false;
+        var eolCount;
         var startLineNumber;
+        var Token;
         var precedingToken;
         var targetToken;
         var newValue;
+        var replacementToken;
 
         while (!precedingToken && currentLineNumber > 0) {
             precedingToken = file.getLastTokenOnLine(currentLineNumber, {
@@ -111,44 +120,40 @@ module.exports.prototype = {
                 precedingToken.loc.start.line <= error.line &&
                 precedingToken.loc.end.line >= error.line) {
 
-                if (precedingToken.type === 'Block') {
-
-                    if (ignoreEmptyLines) {
-                        var blockLines = precedingToken.value.split(/\r\n|\n|\r/);
+                var sourceCode = precedingToken.sourceCodeLines
+                    .map(stripTrailingWs)
+                    .join(linebreak);
 
-                        for (var k = 0; k < blockLines.length; k++) {
+                // Remove `/*`, `*/` and `//` parts
+                var isBlock = precedingToken.type === 'CommentBlock';
+                newValue = sourceCode.slice(2, (-2 * isBlock) || undefined);
 
-                            if (!blockLines[k].match(/^\s*$/) || k === 0) {
-                                blockLines[k] = blockLines[k].split(/\s+$/).join('');
-                            }
-                        }
+                // Make a replacement for existing token
+                Token = precedingToken.constructor;
+                replacementToken = new Token(precedingToken.type, newValue);
 
-                        newValue = blockLines.join(linebreak);
-                    } else {
-                        newValue = precedingToken.value
-                            .split(/[^\S\r\n]+\r\n|[^\S\n]+\n|[^\S\r]+\r/)
-                            .join(linebreak);
-                    }
-                } else {
-                    newValue = precedingToken.value.split(/\s+$/).join('');
-                }
-
-                file.setWhitespaceBefore(precedingToken.nextToken, newValue);
+                precedingToken.parentElement.replaceChild(replacementToken, precedingToken);
                 fixed = true;
             }
         }
 
+        if (targetToken !== null && targetToken.isWhitespace && !fixed) {
+            eolCount = targetToken.loc.end.line - targetToken.loc.start.line + 1;
+            newValue = new Array(eolCount).join(linebreak);
+
+            Token = targetToken.constructor;
+            replacementToken = new Token(targetToken.type, newValue);
+
+            targetToken.parentElement.replaceChild(replacementToken, targetToken);
+            fixed = true;
+        }
+
         if (targetToken !== null && !fixed) {
-            var eolCount = targetToken.loc.start.line - startLineNumber + 1;
-            var targetIndent = '';
-            var targetLine = lines[targetToken.loc.start.line - 1];
-            for (var j = 0, whitespace = targetLine.charAt(j);
-                 whitespace.match(/\s/);
-                 j++, whitespace = targetLine.charAt(j)) {
-                targetIndent += whitespace;
-            }
+            eolCount = targetToken.loc.start.line - startLineNumber + 1;
+            newValue = new Array(eolCount).join(linebreak);
+            newValue += lines[targetToken.loc.start.line - 1].replace(/^(\s*).*?$/, '$1');
 
-            file.setWhitespaceBefore(targetToken, new Array(eolCount).join(linebreak) + targetIndent);
+            file.setWhitespaceBefore(targetToken, newValue);
             fixed = true;
         }
 

test/lib/assertHelpers.js

@@ -46,7 +46,7 @@ var AssertHelpers = {
             it('fix', function() {
                 var result = checker.fixString(options.input);
                 expect(result.errors).to.have.no.errors();
-                expect(result.output).to.equal(options.output);
+                expect(highlightws(result.output)).to.equal(highlightws(options.output));
             });
         }
 
@@ -59,6 +59,13 @@ var AssertHelpers = {
         } else {
             describe(options.name, check);
         }
+
+        function highlightws(str) {
+            return str.replace(/\t/g, '→')
+                .replace(/\r/g, '␍')
+                .replace(/\n/g, '␊')
+                .replace(/\s/g, '·');
+        }
     }
 };
 

test/specs/rules/disallow-trailing-whitespace.js

@@ -2,7 +2,7 @@ var Checker = require('../../../lib/checker');
 var expect = require('chai').expect;
 var reportAndFix = require('../../lib/assertHelpers').reportAndFix;
 
-describe.skip('rules/disallow-trailing-whitespace', function() {
+describe('rules/disallow-trailing-whitespace', function() {
     var rules = { disallowTrailingWhitespace: true };
     var checker;