Merge branch 'rs-dev-issue-2355' into 'master'

MergeRequest#show performance improvements

This is a first pass on improving the performance of the `MergeRequests#show` page. Notable changes:

- The "Commits" tab is loaded lazily, so the initial page load should be much faster for MRs with many commits.
- Relative timestamps via `timeago` are only initialized once per load instead of `O(n^2)`. This greatly improves frontend rendering times for a large number of commits.
- Refactored `User.find_for_commit` to use a single ARel-generated SQL query instead of the old method which resulted in one query, and could result in up to three.

See merge request !838

2 files changed, 104 insertions, 0 deletions

diff --git a/spec/javascripts/fixtures/merge_request_tabs.html.haml b/spec/javascripts/fixtures/merge_request_tabs.html.haml
new file mode 100644
index 00000000000..7624a713948
--- /dev/null
+++ b/spec/javascripts/fixtures/merge_request_tabs.html.haml
@@ -0,0 +1,22 @@
+%ul.nav.nav-tabs.merge-request-tabs
+  %li.notes-tab
+    %a{href: '/foo/bar/merge_requests/1', data: {target: '#notes', action: 'notes', toggle: 'tab'}}
+      Discussion
+  %li.commits-tab
+    %a{href: '/foo/bar/merge_requests/1/commits', data: {target: '#commits', action: 'commits', toggle: 'tab'}}
+      Commits
+  %li.diffs-tab
+    %a{href: '/foo/bar/merge_requests/1/diffs', data: {target: '#diffs', action: 'diffs', toggle: 'tab'}}
+      Diffs
+
+.tab-content
+  #notes.notes.tab-pane
+    Notes Content
+  #commits.commits.tab-pane
+    Commits Content
+  #diffs.diffs.tab-pane
+    Diffs Content
+
+.mr-loading-status
+  .loading
+    Loading Animation
diff --git a/spec/javascripts/merge_request_tabs_spec.js.coffee b/spec/javascripts/merge_request_tabs_spec.js.coffee
new file mode 100644
index 00000000000..6cc96fb68a0
--- /dev/null
+++ b/spec/javascripts/merge_request_tabs_spec.js.coffee
@@ -0,0 +1,82 @@
+#= require merge_request_tabs
+
+describe 'MergeRequestTabs', ->
+  stubLocation = (stubs) ->
+    defaults = {pathname: '', search: '', hash: ''}
+    $.extend(defaults, stubs)
+
+  fixture.preload('merge_request_tabs.html')
+
+  beforeEach ->
+    @class = new MergeRequestTabs()
+    @spies = {
+      ajax:    spyOn($, 'ajax').and.callFake ->
+      history: spyOn(history, 'replaceState').and.callFake ->
+    }
+
+  describe '#activateTab', ->
+    beforeEach ->
+      fixture.load('merge_request_tabs.html')
+      @subject = @class.activateTab
+
+    it 'shows the first tab when action is show', ->
+      @subject('show')
+      expect($('#notes')).toHaveClass('active')
+
+    it 'shows the notes tab when action is notes', ->
+      @subject('notes')
+      expect($('#notes')).toHaveClass('active')
+
+    it 'shows the commits tab when action is commits', ->
+      @subject('commits')
+      expect($('#commits')).toHaveClass('active')
+
+    it 'shows the diffs tab when action is diffs', ->
+      @subject('diffs')
+      expect($('#diffs')).toHaveClass('active')
+
+  describe '#setCurrentAction', ->
+    beforeEach ->
+      @subject = @class.setCurrentAction
+
+    it 'changes from commits', ->
+      @class._location = stubLocation(pathname: '/foo/bar/merge_requests/1/commits')
+
+      expect(@subject('notes')).toBe('/foo/bar/merge_requests/1')
+      expect(@subject('diffs')).toBe('/foo/bar/merge_requests/1/diffs')
+
+    it 'changes from diffs', ->
+      @class._location = stubLocation(pathname: '/foo/bar/merge_requests/1/diffs')
+
+      expect(@subject('notes')).toBe('/foo/bar/merge_requests/1')
+      expect(@subject('commits')).toBe('/foo/bar/merge_requests/1/commits')
+
+    it 'changes from notes', ->
+      @class._location = stubLocation(pathname: '/foo/bar/merge_requests/1')
+
+      expect(@subject('diffs')).toBe('/foo/bar/merge_requests/1/diffs')
+      expect(@subject('commits')).toBe('/foo/bar/merge_requests/1/commits')
+
+    it 'includes search parameters and hash string', ->
+      @class._location = stubLocation({
+        pathname: '/foo/bar/merge_requests/1/diffs'
+        search:   '?view=parallel'
+        hash:     '#L15-35'
+      })
+
+      expect(@subject('show')).toBe('/foo/bar/merge_requests/1?view=parallel#L15-35')
+
+    it 'replaces the current history state', ->
+      @class._location = stubLocation(pathname: '/foo/bar/merge_requests/1')
+      new_state = @subject('commits')
+
+      expect(@spies.history).toHaveBeenCalledWith(
+        {turbolinks: true, url: new_state},
+        document.title,
+        new_state
+      )
+
+    it 'treats "show" like "notes"', ->
+      @class._location = stubLocation(pathname: '/foo/bar/merge_requests/1/commits')
+
+      expect(@subject('show')).toBe('/foo/bar/merge_requests/1')