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

1 files changed, 16 insertions, 2 deletions

diff --git a/app/assets/javascripts/merge_request_tabs.js b/app/assets/javascripts/merge_request_tabs.js
index 6658e4811ce..860ee5df57e 100644
--- a/app/assets/javascripts/merge_request_tabs.js
+++ b/app/assets/javascripts/merge_request_tabs.js
@@ -238,8 +238,11 @@
               _this.expandViewContainer();
             }
             _this.diffsLoaded = true;
-            _this.scrollToElement("#diffs");
-            _this.highlighSelectedLine();
+            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');