Merge branch '21633-permalink-to-collapsed-diff-line-does-not-work' into 'master'

Fixed anchoring diff lines in collapsed diffs

## What does this MR do?

This MR adds the ability to `forceLoad` a collapsed diff from instantiation, on top of this, if it is force loaded, we can pass a callback function to be invoked when the content is loaded.

Now when a MR is loaded, we check for a diff line anchor that is currently within a collapsed diff, we re-instantiate the `singleFileDiff` with the `forceLoad` option. We also pass a callback function that in responsible for highlighting and scrolling to the specified anchor.

## Are there points in the code the reviewer needs to double check?

## Why was this MR needed?

We currently cannot anchor link to collapsed diff lines as the do not auto-expand.

## Screenshots (if relevant)

https://youtu.be/fZVLlP6kchw

## Does this MR meet the acceptance criteria?

- [ ] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- [ ] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [ ] API support added
- Tests
  - [ ] Added for this feature/bug
  - [ ] All builds are passing
- [ ] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [ ] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [ ] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [ ] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?

Closes #21633

See merge request !6285

app/assets/javascripts/merge_request_tabs.js

@@ -238,8 +238,11 @@
               _this.expandViewContainer();
             }
             _this.diffsLoaded = true;
+            var anchoredDiff = gl.utils.getLocationHash();
+            if (anchoredDiff) _this.openAnchoredDiff(anchoredDiff, function() {
               _this.scrollToElement("#diffs");
               _this.highlighSelectedLine();
+            });
             _this.filesCommentButton = $('.files .diff-file').filesCommentButton();
             return $(document).off('click', '.diff-line-num a').on('click', '.diff-line-num a', function(e) {
               e.preventDefault();
@@ -252,6 +255,17 @@
       });
     };
 
+    MergeRequestTabs.prototype.openAnchoredDiff = function(anchoredDiff, cb) {
+      var diffTitle = $('#file-path-' + anchoredDiff);
+      var diffFile = diffTitle.closest('.diff-file');
+      var nothingHereBlock = $('.nothing-here-block:visible', diffFile);
+      if (nothingHereBlock.length) {
+        diffFile.singleFileDiff(true, cb);
+      } else {
+        cb();
+      }
+    };
+
     MergeRequestTabs.prototype.highlighSelectedLine = function() {
       var $diffLine, diffLineTop, hashClassString, locationHash, navBarHeight;
       $('.hll').removeClass('hll');

app/assets/javascripts/single_file_diff.js

@@ -13,7 +13,7 @@
 
     COLLAPSED_HTML = '<div class="nothing-here-block diff-collapsed">This diff is collapsed. <a class="click-to-expand">Click to expand it.</a></div>';
 
-    function SingleFileDiff(file) {
+    function SingleFileDiff(file, forceLoad, cb) {
       this.file = file;
       this.toggleDiff = bind(this.toggleDiff, this);
       this.content = $('.diff-content', this.file);
@@ -32,9 +32,12 @@
         this.$toggleIcon.addClass('fa-caret-down');
       }
       $('.file-title, .click-to-expand', this.file).on('click', this.toggleDiff);
+      if (forceLoad) {
+        this.toggleDiff(null, cb);
+      }
     }
 
-    SingleFileDiff.prototype.toggleDiff = function(e) {
+    SingleFileDiff.prototype.toggleDiff = function(e, cb) {
       var $target = $(e.target);
       if (!$target.hasClass('file-title') && !$target.hasClass('click-to-expand') && !$target.hasClass('diff-toggle-caret')) return;
       this.isOpen = !this.isOpen;
@@ -54,11 +57,11 @@
         }
       } else {
         this.$toggleIcon.addClass('fa-caret-down').removeClass('fa-caret-right');
-        return this.getContentHTML();
+        return this.getContentHTML(cb);
       }
     };
 
-    SingleFileDiff.prototype.getContentHTML = function() {
+    SingleFileDiff.prototype.getContentHTML = function(cb) {
       this.collapsedContent.hide();
       this.loadingContent.show();
       $.get(this.diffForPath, (function(_this) {
@@ -76,6 +79,8 @@
           if (typeof DiffNotesApp !== 'undefined') {
             DiffNotesApp.compileComponents();
           }
+
+          if (cb) cb();
         };
       })(this));
     };
@@ -84,10 +89,10 @@
 
   })();
 
-  $.fn.singleFileDiff = function() {
+  $.fn.singleFileDiff = function(forceLoad, cb) {
     return this.each(function() {
-      if (!$.data(this, 'singleFileDiff')) {
-        return $.data(this, 'singleFileDiff', new SingleFileDiff(this));
+      if (!$.data(this, 'singleFileDiff') || forceLoad) {
+        return $.data(this, 'singleFileDiff', new SingleFileDiff(this, forceLoad, cb));
       }
     });
   };