---
layout: post
title: a post with code diff
date: 2024-01-27 19:22:00
description: this is how you can display code diffs
tags: formatting code
categories: sample-posts
code_diff: true
---

You can display diff code by using the regular markdown syntax:

````markdown
```diff
diff --git a/sample.js b/sample.js
index 0000001..0ddf2ba
--- a/sample.js
+++ b/sample.js
@@ -1 +1 @@
-console.log("Hello World!")
+console.log("Hello from Diff2Html!")
```
````

Which generates:

```diff
diff --git a/sample.js b/sample.js
index 0000001..0ddf2ba
--- a/sample.js
+++ b/sample.js
@@ -1 +1 @@
-console.log("Hello World!")
+console.log("Hello from Diff2Html!")
```

But this is difficult to read, specially if you have a large diff. You can use [diff2html](https://diff2html.xyz/) to display a more readable version of the diff. For this, just use `diff2html` instead of `diff` for the code block language:

````markdown
```diff2html
diff --git a/sample.js b/sample.js
index 0000001..0ddf2ba
--- a/sample.js
+++ b/sample.js
@@ -1 +1 @@
-console.log("Hello World!")
+console.log("Hello from Diff2Html!")
```
````

If we use a longer example, for example [this commit from diff2html](https://github.com/rtfpessoa/diff2html/commit/c2c253d3e3f8b8b267f551e659f72b44ca2ac927), it will generate the following output:

```diff2html
From 2aaae31cc2a37bfff83430c2c914b140bee59b6a Mon Sep 17 00:00:00 2001
From: Rodrigo Fernandes <rtfrodrigo@gmail.com>
Date: Sun, 9 Oct 2016 16:41:54 +0100
Subject: [PATCH 1/2] Initial template override support

---
 scripts/hulk.js                    |  4 ++--
 src/diff2html.js                   |  3 +--
 src/file-list-printer.js           | 11 ++++++++---
 src/hoganjs-utils.js               | 29 +++++++++++++++++------------
 src/html-printer.js                |  6 ++++++
 src/line-by-line-printer.js        |  6 +++++-
 src/side-by-side-printer.js        |  6 +++++-
 test/file-list-printer-tests.js    |  2 +-
 test/hogan-cache-tests.js          | 18 +++++++++++++++---
 test/line-by-line-tests.js         |  3 +--
 test/side-by-side-printer-tests.js |  3 +--
 11 files changed, 62 insertions(+), 29 deletions(-)

diff --git a/scripts/hulk.js b/scripts/hulk.js
index 5a793c18..a4b1a4d5 100755
--- a/scripts/hulk.js
+++ b/scripts/hulk.js
@@ -173,11 +173,11 @@ function namespace(name) {
 // write a template foreach file that matches template extension
 templates = extractFiles(options.argv.remain)
   .map(function(file) {
-    var openedFile = fs.readFileSync(file, 'utf-8');
+    var openedFile = fs.readFileSync(file, 'utf-8').trim();
     var name;
     if (!openedFile) return;
     name = namespace(path.basename(file).replace(/\..*$/, ''));
-    openedFile = removeByteOrderMark(openedFile.trim());
+    openedFile = removeByteOrderMark(openedFile);
     openedFile = wrap(file, name, openedFile);
     if (!options.outputdir) return openedFile;
     fs.writeFileSync(path.join(options.outputdir, name + '.js')
diff --git a/src/diff2html.js b/src/diff2html.js
index 21b0119e..64e138f5 100644
--- a/src/diff2html.js
+++ b/src/diff2html.js
@@ -7,7 +7,6 @@

 (function() {
   var diffParser = require('./diff-parser.js').DiffParser;
-  var fileLister = require('./file-list-printer.js').FileListPrinter;
   var htmlPrinter = require('./html-printer.js').HtmlPrinter;

   function Diff2Html() {
@@ -43,7 +42,7 @@

     var fileList = '';
     if (configOrEmpty.showFiles === true) {
-      fileList = fileLister.generateFileList(diffJson, configOrEmpty);
+      fileList = htmlPrinter.generateFileListSummary(diffJson, configOrEmpty);
     }

     var diffOutput = '';
diff --git a/src/file-list-printer.js b/src/file-list-printer.js
index e408d9b2..1e0a2c61 100644
--- a/src/file-list-printer.js
+++ b/src/file-list-printer.js
@@ -8,11 +8,16 @@
 (function() {
   var printerUtils = require('./printer-utils.js').PrinterUtils;

-  var hoganUtils = require('./hoganjs-utils.js').HoganJsUtils;
+  var hoganUtils;
+
   var baseTemplatesPath = 'file-summary';
   var iconsBaseTemplatesPath = 'icon';

-  function FileListPrinter() {
+  function FileListPrinter(config) {
+    this.config = config;
+
+    var HoganJsUtils = require('./hoganjs-utils.js').HoganJsUtils;
+    hoganUtils = new HoganJsUtils(config);
   }

   FileListPrinter.prototype.generateFileList = function(diffFiles) {
@@ -38,5 +43,5 @@
     });
   };

-  module.exports.FileListPrinter = new FileListPrinter();
+  module.exports.FileListPrinter = FileListPrinter;
 })();
diff --git a/src/hoganjs-utils.js b/src/hoganjs-utils.js
index 9949e5fa..0dda08d7 100644
--- a/src/hoganjs-utils.js
+++ b/src/hoganjs-utils.js
@@ -8,18 +8,19 @@
 (function() {
   var fs = require('fs');
   var path = require('path');
-
   var hogan = require('hogan.js');

   var hoganTemplates = require('./templates/diff2html-templates.js');

-  var templatesPath = path.resolve(__dirname, 'templates');
+  var extraTemplates;

-  function HoganJsUtils() {
+  function HoganJsUtils(configuration) {
+    this.config = configuration || {};
+    extraTemplates = this.config.templates || {};
   }

-  HoganJsUtils.prototype.render = function(namespace, view, params, configuration) {
-    var template = this.template(namespace, view, configuration);
+  HoganJsUtils.prototype.render = function(namespace, view, params) {
+    var template = this.template(namespace, view);
     if (template) {
       return template.render(params);
     }
@@ -27,17 +28,16 @@
     return null;
   };

-  HoganJsUtils.prototype.template = function(namespace, view, configuration) {
-    var config = configuration || {};
+  HoganJsUtils.prototype.template = function(namespace, view) {
     var templateKey = this._templateKey(namespace, view);

-    return this._getTemplate(templateKey, config);
+    return this._getTemplate(templateKey);
   };

-  HoganJsUtils.prototype._getTemplate = function(templateKey, config) {
+  HoganJsUtils.prototype._getTemplate = function(templateKey) {
     var template;

-    if (!config.noCache) {
+    if (!this.config.noCache) {
       template = this._readFromCache(templateKey);
     }

@@ -53,6 +53,7 @@

     try {
       if (fs.readFileSync) {
+        var templatesPath = path.resolve(__dirname, 'templates');
         var templatePath = path.join(templatesPath, templateKey);
         var templateContent = fs.readFileSync(templatePath + '.mustache', 'utf8');
         template = hogan.compile(templateContent);
@@ -66,12 +67,16 @@
   };

   HoganJsUtils.prototype._readFromCache = function(templateKey) {
-    return hoganTemplates[templateKey];
+    return extraTemplates[templateKey] || hoganTemplates[templateKey];
   };

   HoganJsUtils.prototype._templateKey = function(namespace, view) {
     return namespace + '-' + view;
   };

-  module.exports.HoganJsUtils = new HoganJsUtils();
+  HoganJsUtils.prototype.compile = function(templateStr) {
+    return hogan.compile(templateStr);
+  };
+
+  module.exports.HoganJsUtils = HoganJsUtils;
 })();
diff --git a/src/html-printer.js b/src/html-printer.js
index 585d5b66..13f83047 100644
--- a/src/html-printer.js
+++ b/src/html-printer.js
@@ -8,6 +8,7 @@
 (function() {
   var LineByLinePrinter = require('./line-by-line-printer.js').LineByLinePrinter;
   var SideBySidePrinter = require('./side-by-side-printer.js').SideBySidePrinter;
+  var FileListPrinter = require('./file-list-printer.js').FileListPrinter;

   function HtmlPrinter() {
   }
@@ -22,5 +23,10 @@
     return sideBySidePrinter.generateSideBySideJsonHtml(diffFiles);
   };

+  HtmlPrinter.prototype.generateFileListSummary = function(diffJson, config) {
+    var fileListPrinter = new FileListPrinter(config);
+    return fileListPrinter.generateFileList(diffJson);
+  };
+
   module.exports.HtmlPrinter = new HtmlPrinter();
 })();
diff --git a/src/line-by-line-printer.js b/src/line-by-line-printer.js
index b07eb53c..d230bedd 100644
--- a/src/line-by-line-printer.js
+++ b/src/line-by-line-printer.js
@@ -11,7 +11,8 @@
   var utils = require('./utils.js').Utils;
   var Rematch = require('./rematch.js').Rematch;

-  var hoganUtils = require('./hoganjs-utils.js').HoganJsUtils;
+  var hoganUtils;
+
   var genericTemplatesPath = 'generic';
   var baseTemplatesPath = 'line-by-line';
   var iconsBaseTemplatesPath = 'icon';
@@ -19,6 +20,9 @@

   function LineByLinePrinter(config) {
     this.config = config;
+
+    var HoganJsUtils = require('./hoganjs-utils.js').HoganJsUtils;
+    hoganUtils = new HoganJsUtils(config);
   }

   LineByLinePrinter.prototype.makeFileDiffHtml = function(file, diffs) {
diff --git a/src/side-by-side-printer.js b/src/side-by-side-printer.js
index bbf1dc8d..5e3033b3 100644
--- a/src/side-by-side-printer.js
+++ b/src/side-by-side-printer.js
@@ -11,7 +11,8 @@
   var utils = require('./utils.js').Utils;
   var Rematch = require('./rematch.js').Rematch;

-  var hoganUtils = require('./hoganjs-utils.js').HoganJsUtils;
+  var hoganUtils;
+
   var genericTemplatesPath = 'generic';
   var baseTemplatesPath = 'side-by-side';
   var iconsBaseTemplatesPath = 'icon';
@@ -26,6 +27,9 @@

   function SideBySidePrinter(config) {
     this.config = config;
+
+    var HoganJsUtils = require('./hoganjs-utils.js').HoganJsUtils;
+    hoganUtils = new HoganJsUtils(config);
   }

   SideBySidePrinter.prototype.makeDiffHtml = function(file, diffs) {
diff --git a/test/file-list-printer-tests.js b/test/file-list-printer-tests.js
index a502a46f..60ea3208 100644
--- a/test/file-list-printer-tests.js
+++ b/test/file-list-printer-tests.js
@@ -1,6 +1,6 @@
 var assert = require('assert');

-var fileListPrinter = require('../src/file-list-printer.js').FileListPrinter;
+var fileListPrinter = new (require('../src/file-list-printer.js').FileListPrinter)();

 describe('FileListPrinter', function() {
   describe('generateFileList', function() {
diff --git a/test/hogan-cache-tests.js b/test/hogan-cache-tests.js
index 190bf6f8..3bb754ac 100644
--- a/test/hogan-cache-tests.js
+++ b/test/hogan-cache-tests.js
@@ -1,6 +1,6 @@
 var assert = require('assert');

-var HoganJsUtils = require('../src/hoganjs-utils.js').HoganJsUtils;
+var HoganJsUtils = new (require('../src/hoganjs-utils.js').HoganJsUtils)();
 var diffParser = require('../src/diff-parser.js').DiffParser;

 describe('HoganJsUtils', function() {
@@ -21,16 +21,28 @@ describe('HoganJsUtils', function() {
       });
       assert.equal(emptyDiffHtml, result);
     });
+
     it('should render view without cache', function() {
       var result = HoganJsUtils.render('generic', 'empty-diff', {
         contentClass: 'd2h-code-line',
         diffParser: diffParser
       }, {noCache: true});
-      assert.equal(emptyDiffHtml + '\n', result);
+      assert.equal(emptyDiffHtml, result);
     });
+
     it('should return null if template is missing', function() {
-      var result = HoganJsUtils.render('generic', 'missing-template', {}, {noCache: true});
+      var hoganUtils = new (require('../src/hoganjs-utils.js').HoganJsUtils)({noCache: true});
+      var result = hoganUtils.render('generic', 'missing-template', {});
       assert.equal(null, result);
     });
+
+    it('should allow templates to be overridden', function() {
+      var emptyDiffTemplate = HoganJsUtils.compile('<p>{{myName}}</p>');
+
+      var config = {templates: {'generic-empty-diff': emptyDiffTemplate}};
+      var hoganUtils = new (require('../src/hoganjs-utils.js').HoganJsUtils)(config);
+      var result = hoganUtils.render('generic', 'empty-diff', {myName: 'Rodrigo Fernandes'});
+      assert.equal('<p>Rodrigo Fernandes</p>', result);
+    });
   });
 });
diff --git a/test/line-by-line-tests.js b/test/line-by-line-tests.js
index 1cd92073..8869b3df 100644
--- a/test/line-by-line-tests.js
+++ b/test/line-by-line-tests.js
@@ -14,7 +14,7 @@ describe('LineByLinePrinter', function() {
         '            File without changes\n' +
         '        </div>\n' +
         '    </td>\n' +
-        '</tr>\n';
+        '</tr>';

       assert.equal(expected, fileHtml);
     });
@@ -422,7 +422,6 @@ describe('LineByLinePrinter', function() {
         '        </div>\n' +
         '    </td>\n' +
         '</tr>\n' +
-        '\n' +
         '                </tbody>\n' +
         '            </table>\n' +
         '        </div>\n' +
diff --git a/test/side-by-side-printer-tests.js b/test/side-by-side-printer-tests.js
index 76625f8e..771daaa5 100644
--- a/test/side-by-side-printer-tests.js
+++ b/test/side-by-side-printer-tests.js
@@ -14,7 +14,7 @@ describe('SideBySidePrinter', function() {
         '            File without changes\n' +
         '        </div>\n' +
         '    </td>\n' +
-        '</tr>\n';
+        '</tr>';

       assert.equal(expectedRight, fileHtml.right);
       assert.equal(expectedLeft, fileHtml.left);
@@ -324,7 +324,6 @@ describe('SideBySidePrinter', function() {
         '        </div>\n' +
         '    </td>\n' +
         '</tr>\n' +
-        '\n' +
         '                    </tbody>\n' +
         '                </table>\n' +
         '            </div>\n' +

From f3cadb96677d0eb82fc2752dc3ffbf35ca9b5bdb Mon Sep 17 00:00:00 2001
From: Rodrigo Fernandes <rtfrodrigo@gmail.com>
Date: Sat, 15 Oct 2016 13:21:22 +0100
Subject: [PATCH 2/2] Allow uncompiled templates

---
 README.md                 |  3 +++
 src/hoganjs-utils.js      |  7 +++++++
 test/hogan-cache-tests.js | 24 +++++++++++++++++++++++-
 3 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/README.md b/README.md
index 132c8a28..46909f25 100644
--- a/README.md
+++ b/README.md
@@ -98,6 +98,9 @@ The HTML output accepts a Javascript object with configuration. Possible options
   - `synchronisedScroll`: scroll both panes in side-by-side mode: `true` or `false`, default is `false`
   - `matchWordsThreshold`: similarity threshold for word matching, default is 0.25
   - `matchingMaxComparisons`: perform at most this much comparisons for line matching a block of changes, default is `2500`
+  - `templates`: object with previously compiled templates to replace parts of the html
+  - `rawTemplates`: object with raw not compiled templates to replace parts of the html
+  > For more information regarding the possible templates look into [src/templates](https://github.com/rtfpessoa/diff2html/tree/master/src/templates)

 ## Diff2HtmlUI Helper

diff --git a/src/hoganjs-utils.js b/src/hoganjs-utils.js
index 0dda08d7..b2e9c275 100644
--- a/src/hoganjs-utils.js
+++ b/src/hoganjs-utils.js
@@ -17,6 +17,13 @@
   function HoganJsUtils(configuration) {
     this.config = configuration || {};
     extraTemplates = this.config.templates || {};
+
+    var rawTemplates = this.config.rawTemplates || {};
+    for (var templateName in rawTemplates) {
+      if (rawTemplates.hasOwnProperty(templateName)) {
+        if (!extraTemplates[templateName]) extraTemplates[templateName] = this.compile(rawTemplates[templateName]);
+      }
+    }
   }

   HoganJsUtils.prototype.render = function(namespace, view, params) {
diff --git a/test/hogan-cache-tests.js b/test/hogan-cache-tests.js
index 3bb754ac..a34839c0 100644
--- a/test/hogan-cache-tests.js
+++ b/test/hogan-cache-tests.js
@@ -36,7 +36,7 @@ describe('HoganJsUtils', function() {
       assert.equal(null, result);
     });

-    it('should allow templates to be overridden', function() {
+    it('should allow templates to be overridden with compiled templates', function() {
       var emptyDiffTemplate = HoganJsUtils.compile('<p>{{myName}}</p>');

       var config = {templates: {'generic-empty-diff': emptyDiffTemplate}};
@@ -44,5 +44,27 @@ describe('HoganJsUtils', function() {
       var result = hoganUtils.render('generic', 'empty-diff', {myName: 'Rodrigo Fernandes'});
       assert.equal('<p>Rodrigo Fernandes</p>', result);
     });
+
+    it('should allow templates to be overridden with uncompiled templates', function() {
+      var emptyDiffTemplate = '<p>{{myName}}</p>';
+
+      var config = {rawTemplates: {'generic-empty-diff': emptyDiffTemplate}};
+      var hoganUtils = new (require('../src/hoganjs-utils.js').HoganJsUtils)(config);
+      var result = hoganUtils.render('generic', 'empty-diff', {myName: 'Rodrigo Fernandes'});
+      assert.equal('<p>Rodrigo Fernandes</p>', result);
+    });
+
+    it('should allow templates to be overridden giving priority to compiled templates', function() {
+      var emptyDiffTemplate = HoganJsUtils.compile('<p>{{myName}}</p>');
+      var emptyDiffTemplateUncompiled = '<p>Not used!</p>';
+
+      var config = {
+        templates: {'generic-empty-diff': emptyDiffTemplate},
+        rawTemplates: {'generic-empty-diff': emptyDiffTemplateUncompiled}
+      };
+      var hoganUtils = new (require('../src/hoganjs-utils.js').HoganJsUtils)(config);
+      var result = hoganUtils.render('generic', 'empty-diff', {myName: 'Rodrigo Fernandes'});
+      assert.equal('<p>Rodrigo Fernandes</p>', result);
+    });
   });
 });
```