Merge branch 'fix-api-sorting' into 'master'

Fix API issues sorting

## What does this MR do?

Fix the sorting of issues in the API.

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

Instead of removing the '_at' suffix manually, we could add those versions to the `Sortable` concern instead.

## Why was this MR needed?

There were a couple of bugs:

* The global and project-specific issues endpoints wouldn't sort at all.
* Group sorting would work, but only if you applied two undocumented workarounds:
  * Always pass both `order_by` and `sort` (both are optional, so only one should be needed to change ordering).
  * Instead of passing `created_at` or `updated_at`, you needed to pass `created` or `updated`.

This makes the API implementation match the docs.

## Does this MR meet the acceptance criteria?

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

## What are the relevant issue numbers?

Closes https://gitlab.com/gitlab-org/gitlab-ee/issues/983.

See merge request !6281

1 files changed, 9 insertions, 3 deletions

diff --git a/lib/api/issues.rb b/lib/api/issues.rb
index 556684187d8..c9689e6f8ef 100644
--- a/lib/api/issues.rb
+++ b/lib/api/issues.rb
@@ -41,7 +41,8 @@ module API
         issues = current_user.issues.inc_notes_with_associations
         issues = filter_issues_state(issues, params[:state]) unless params[:state].nil?
         issues = filter_issues_labels(issues, params[:labels]) unless params[:labels].nil?
-        issues.reorder(issuable_order_by => issuable_sort)
+        issues = issues.reorder(issuable_order_by => issuable_sort)
+
         present paginate(issues), with: Entities::Issue, current_user: current_user
       end
     end
@@ -73,7 +74,11 @@ module API
         params[:group_id] = group.id
         params[:milestone_title] = params.delete(:milestone)
         params[:label_name] = params.delete(:labels)
-        params[:sort] = "#{params.delete(:order_by)}_#{params.delete(:sort)}" if params[:order_by] && params[:sort]
+
+        if params[:order_by] || params[:sort]
+          # The Sortable concern takes 'created_desc', not 'created_at_desc' (for example)
+          params[:sort] = "#{issuable_order_by.sub('_at', '')}_#{issuable_sort}"
+        end
 
         issues = IssuesFinder.new(current_user, params).execute
 
@@ -113,7 +118,8 @@ module API
           issues = filter_issues_milestone(issues, params[:milestone])
         end
 
-        issues.reorder(issuable_order_by => issuable_sort)
+        issues = issues.reorder(issuable_order_by => issuable_sort)
+
         present paginate(issues), with: Entities::Issue, current_user: current_user
       end