Merge branch '2489-soft-delete-issues' into 'master'

Soft delete issuables

Fixes #2489 

What still needs to happen: research on the indexes, the gem suggests a [lot of changes](https://github.com/rubysherpas/paranoia#about-indexes) though this is probably a good idea to discuss and I'm unsure on the impact of an omnibus upgrade as I suspect creating about 10 new indexes has a large impact on the downtime.

TODO: 
- [x] Also group owners can ***soft*** delete
- [x] Button should be hidden

See merge request !2982

9 files changed, 44 insertions, 7 deletions

diff --git a/app/controllers/concerns/issuable_actions.rb b/app/controllers/concerns/issuable_actions.rb
new file mode 100644
index 00000000000..f40b62446e5
--- /dev/null
+++ b/app/controllers/concerns/issuable_actions.rb
@@ -0,0 +1,23 @@
+module IssuableActions
+  extend ActiveSupport::Concern
+
+  included do
+    before_action :authorize_destroy_issuable!, only: :destroy
+  end
+
+  def destroy
+    issuable.destroy
+
+    name = issuable.class.name.titleize.downcase
+    flash[:notice] = "The #{name} was successfully deleted."
+    redirect_to polymorphic_path([@project.namespace.becomes(Namespace), @project, issuable.class])
+  end
+
+  private
+
+  def authorize_destroy_issuable!
+    unless current_user.can?(:"destroy_#{issuable.to_ability_name}", issuable)
+      return access_denied!
+    end
+  end
+end
diff --git a/app/controllers/projects/issues_controller.rb b/app/controllers/projects/issues_controller.rb
index a3c28a82d26..877b39c9b1b 100644
--- a/app/controllers/projects/issues_controller.rb
+++ b/app/controllers/projects/issues_controller.rb
@@ -1,5 +1,6 @@
 class Projects::IssuesController < Projects::ApplicationController
   include ToggleSubscriptionAction
+  include IssuableActions
 
   before_action :module_enabled
   before_action :issue, only: [:edit, :update, :show]
@@ -133,6 +134,7 @@ class Projects::IssuesController < Projects::ApplicationController
                end
   end
   alias_method :subscribable_resource, :issue
+  alias_method :issuable, :issue
 
   def authorize_read_issue!
     return render_404 unless can?(current_user, :read_issue, @issue)
diff --git a/app/controllers/projects/merge_requests_controller.rb b/app/controllers/projects/merge_requests_controller.rb
index 99cb5981940..b830d777752 100644
--- a/app/controllers/projects/merge_requests_controller.rb
+++ b/app/controllers/projects/merge_requests_controller.rb
@@ -1,6 +1,7 @@
 class Projects::MergeRequestsController < Projects::ApplicationController
   include ToggleSubscriptionAction
   include DiffHelper
+  include IssuableActions
 
   before_action :module_enabled
   before_action :merge_request, only: [
@@ -255,6 +256,7 @@ class Projects::MergeRequestsController < Projects::ApplicationController
     @merge_request ||= @project.merge_requests.find_by!(iid: params[:id])
   end
   alias_method :subscribable_resource, :merge_request
+  alias_method :issuable, :merge_request
 
   def closes_issues
     @closes_issues ||= @merge_request.closes_issues
diff --git a/app/models/ability.rb b/app/models/ability.rb
index e22da4806e6..40c529e8117 100644
--- a/app/models/ability.rb
+++ b/app/models/ability.rb
@@ -235,7 +235,9 @@ class Ability
         :rename_project,
         :remove_project,
         :archive_project,
-        :remove_fork_project
+        :remove_fork_project,
+        :destroy_merge_request,
+        :destroy_issue
       ]
     end
 
diff --git a/app/models/concerns/internal_id.rb b/app/models/concerns/internal_id.rb
index 821ed54fb98..51288094ef1 100644
--- a/app/models/concerns/internal_id.rb
+++ b/app/models/concerns/internal_id.rb
@@ -7,7 +7,10 @@ module InternalId
   end
 
   def set_iid
-    max_iid = project.send(self.class.name.tableize).maximum(:iid)
+    records = project.send(self.class.name.tableize)
+    records = records.with_deleted if self.paranoid?
+    max_iid = records.maximum(:iid)
+
     self.iid = max_iid.to_i + 1
   end
 
diff --git a/app/models/concerns/issuable.rb b/app/models/concerns/issuable.rb
index 9ab72652190..476e1ce7af0 100644
--- a/app/models/concerns/issuable.rb
+++ b/app/models/concerns/issuable.rb
@@ -58,6 +58,8 @@ module Issuable
     attr_mentionable :description, cache: true
     participant :author, :assignee, :notes_with_associations
     strip_attributes :title
+
+    acts_as_paranoid
   end
 
   module ClassMethods
diff --git a/app/views/projects/issues/show.html.haml b/app/views/projects/issues/show.html.haml
index 52df3de8a27..6fa059cbe68 100644
--- a/app/views/projects/issues/show.html.haml
+++ b/app/views/projects/issues/show.html.haml
@@ -45,7 +45,6 @@
       - if can?(current_user, :update_issue, @issue)
         = link_to 'Reopen issue', issue_path(@issue, issue: {state_event: :reopen}, status_only: true, format: 'json'), data: {no_turbolink: true}, class: "btn btn-nr btn-grouped btn-reopen #{issue_button_visibility(@issue, false)}", title: 'Reopen issue'
         = link_to 'Close issue', issue_path(@issue, issue: {state_event: :close}, status_only: true, format: 'json'), data: {no_turbolink: true}, class: "btn btn-nr btn-grouped btn-close #{issue_button_visibility(@issue, true)}", title: 'Close issue'
-
         = link_to edit_namespace_project_issue_path(@project.namespace, @project, @issue), class: 'btn btn-nr btn-grouped issuable-edit' do
           = icon('pencil-square-o')
           Edit
diff --git a/app/views/projects/merge_requests/show/_mr_title.html.haml b/app/views/projects/merge_requests/show/_mr_title.html.haml
index eeb605e2dc5..ab4b1f14be5 100644
--- a/app/views/projects/merge_requests/show/_mr_title.html.haml
+++ b/app/views/projects/merge_requests/show/_mr_title.html.haml
@@ -29,7 +29,7 @@
       - if @merge_request.open?
         = link_to 'Close', merge_request_path(@merge_request, merge_request: { state_event: :close }), method: :put, class: 'btn btn-nr btn-grouped btn-close', title: 'Close merge request'
         = link_to edit_namespace_project_merge_request_path(@project.namespace, @project, @merge_request), class: 'btn btn-nr btn-grouped issuable-edit', id: 'edit_merge_request' do
-          %i.fa.fa-pencil-square-o
+          = icon('pencil-square-o')
           Edit
       - if @merge_request.closed?
         = link_to 'Reopen', merge_request_path(@merge_request, merge_request: {state_event: :reopen }), method: :put, class: 'btn btn-nr btn-grouped btn-reopen reopen-mr-link', title: 'Reopen merge request'
diff --git a/app/views/shared/issuable/_form.html.haml b/app/views/shared/issuable/_form.html.haml
index 1740b128ee4..551f0cc0b51 100644
--- a/app/views/shared/issuable/_form.html.haml
+++ b/app/views/shared/issuable/_form.html.haml
@@ -127,7 +127,11 @@
       for this project.
 
   - if issuable.new_record?
-    - cancel_project = issuable.source_project
+    = link_to 'Cancel', namespace_project_issues_path(@project.namespace, @project), class: 'btn btn-cancel'
   - else
-    - cancel_project = issuable.project
-  = link_to 'Cancel', [cancel_project.namespace.becomes(Namespace), cancel_project, issuable], class: 'btn btn-cancel'
+    .pull-right
+      - if current_user.can?(:"destroy_#{issuable.to_ability_name}", @project)
+        = link_to polymorphic_path([@project.namespace.becomes(Namespace), @project, issuable]), method: :delete, class: 'btn btn-grouped' do
+          = icon('trash-o')
+          Delete
+      = link_to 'Cancel', namespace_project_issue_path(@project.namespace, @project, issuable), class: 'btn btn-grouped btn-cancel'