Only count active milestones as started

The Upcoming milestone filter only considers active milestones, but the
Started one included closed milestones, too. This was inconsistent.

app/finders/issuable_finder.rb

@@ -496,7 +496,7 @@ class IssuableFinder
         upcoming_ids = Milestone.upcoming_ids(projects, related_groups)
         items = items.left_joins_milestones.where(milestone_id: upcoming_ids)
       elsif filter_by_started_milestone?
-        items = items.left_joins_milestones.where('milestones.start_date <= NOW()')
+        items = items.left_joins_milestones.merge(Milestone.started)
       else
         items = items.with_milestone(params[:milestone_title])
       end

app/models/milestone.rb

@@ -37,6 +37,7 @@ class Milestone < ActiveRecord::Base
   scope :active, -> { with_state(:active) }
   scope :closed, -> { with_state(:closed) }
   scope :for_projects, -> { where(group: nil).includes(:project) }
+  scope :started, -> { active.where('milestones.start_date <= CURRENT_DATE') }
   scope :for_projects_and_groups, -> (projects, groups) do
     projects = projects.compact if projects.is_a? Array

changelogs/unreleased/only-counted-active-milestones-as-started.yml

+---
+title: Only consider active milestones when using the special Started milestone filter
+merge_request:
+author:
+type: fixed

doc/user/project/milestones/index.md

@@ -92,7 +92,7 @@ When filtering by milestone, in addition to choosing a specific project mileston
 - **None**: Show issues or merge requests with no assigned milestone.
 - **Any**: Show issues or merge requests that have an assigned milestone.
 - **Upcoming**: Show issues or merge requests that have been assigned the open milestone that has the next upcoming due date (i.e. nearest due date in the future).
-- **Started**: Show issues or merge requests that have an assigned milestone with a start date that is before today.
+- **Started**: Show issues or merge requests that have an open assigned milestone with a start date that is before today.
 ## Milestone view

spec/finders/issues_finder_spec.rb

@@ -220,6 +220,7 @@ describe IssuesFinder do
         let(:yesterday) { Date.today - 1.day }
         let(:tomorrow) { Date.today + 1.day }
         let(:two_days_ago) { Date.today - 2.days }
+        let(:three_days_ago) { Date.today - 3.days }
         let(:milestones) do
           [
@@ -227,6 +228,8 @@ describe IssuesFinder do
             create(:milestone, project: project_started_1_and_2, title: '1.0', start_date: two_days_ago),
             create(:milestone, project: project_started_1_and_2, title: '2.0', start_date: yesterday),
             create(:milestone, project: project_started_1_and_2, title: '3.0', start_date: tomorrow),
+            create(:milestone, :closed, project: project_started_1_and_2, title: '4.0', start_date: three_days_ago),
+            create(:milestone, :closed, project: project_started_8, title: '6.0', start_date: three_days_ago),
             create(:milestone, project: project_started_8, title: '7.0'),
             create(:milestone, project: project_started_8, title: '8.0', start_date: yesterday),
             create(:milestone, project: project_started_8, title: '9.0', start_date: tomorrow)