Allows to filter issues by `Any milestone` in the API

In GET `api/v4/projects/:id/issues` the user can filter issues
that have an assigned milestone through the parameter
`milestone=Any+Milestone`.

app/finders/issuable_finder.rb

@@ -424,6 +424,10 @@ class IssuableFinder
     params[:milestone_title] == Milestone::Upcoming.name
   end
 
+  def filter_by_any_milestone?
+    params[:milestone_title] == Milestone::Any.title
+  end
+
   def filter_by_started_milestone?
     params[:milestone_title] == Milestone::Started.name
   end
@@ -433,6 +437,8 @@ class IssuableFinder
     if milestones?
       if filter_by_no_milestone?
         items = items.left_joins_milestones.where(milestone_id: [-1, nil])
+      elsif filter_by_any_milestone?
+        items = items.any_milestone
       elsif filter_by_upcoming_milestone?
         upcoming_ids = Milestone.upcoming_ids_by_projects(projects(items))
         items = items.left_joins_milestones.where(milestone_id: upcoming_ids)

app/models/concerns/issuable.rb

@@ -76,6 +76,7 @@ module Issuable
     scope :recent, -> { reorder(id: :desc) }
     scope :of_projects, ->(ids) { where(project_id: ids) }
     scope :of_milestones, ->(ids) { where(milestone_id: ids) }
+    scope :any_milestone, -> { where('milestone_id IS NOT NULL') }
     scope :with_milestone, ->(title) { left_joins_milestones.where(milestones: { title: title }) }
     scope :opened, -> { with_state(:opened) }
     scope :only_opened, -> { with_state(:opened) }

changelogs/unreleased/51748-filter-any-milestone-via-api.yml

+---
+title: Allows to filter issues by Any milestone in the API
+merge_request: 22080
+author: Jacopo Beschi @jacopo-beschi
+type: added

doc/api/issues.md

@@ -37,7 +37,7 @@ GET /issues?my_reaction_emoji=star
 | ------------------- | ---------------- | ---------- | --------------------------------------------------------------------------------------------------------------------------------------------------- |
 | `state`             | string           | no         | Return all issues or just those that are `opened` or `closed`                                                                                       |
 | `labels`            | string           | no         | Comma-separated list of label names, issues must have all labels to be returned. `No+Label` lists all issues with no labels                         |
-| `milestone`         | string           | no         | The milestone title. `No+Milestone` lists all issues with no milestone                                                                                                                                |
+| `milestone`         | string           | no         | The milestone title. `No+Milestone` lists all issues with no milestone. `Any+Milestone` lists all issues that have an assigned milestone            |
 | `scope`             | string           | no         | Return issues for the given scope: `created_by_me`, `assigned_to_me` or `all`. Defaults to `created_by_me`<br> For versions before 11.0, use the now deprecated `created-by-me` or `assigned-to-me` scopes instead.<br> _([Introduced][ce-13004] in GitLab 9.5. [Changed to snake_case][ce-18935] in GitLab 11.0)_ |
 | `author_id`         | integer          | no         | Return issues created by the given user `id`. Combine with `scope=all` or `scope=assigned_to_me`. _([Introduced][ce-13004] in GitLab 9.5)_          |
 | `assignee_id`       | integer          | no         | Return issues assigned to the given user `id` _([Introduced][ce-13004] in GitLab 9.5)_                                                              |

spec/finders/issues_finder_spec.rb

@@ -125,6 +125,14 @@ describe IssuesFinder do
         end
       end
 
+      context 'filtering by any milestone' do
+        let(:params) { { milestone_title: Milestone::Any.title } }
+
+        it 'returns issues with any assigned milestone' do
+          expect(issues).to contain_exactly(issue1)
+        end
+      end
+
       context 'filtering by upcoming milestone' do
         let(:params) { { milestone_title: Milestone::Upcoming.name } }
 

spec/requests/api/issues_spec.rb

@@ -56,6 +56,7 @@ describe API::Issues do
   let!(:note) { create(:note_on_issue, author: user, project: project, noteable: issue) }
 
   let(:no_milestone_title) { URI.escape(Milestone::None.title) }
+  let(:any_milestone_title) { URI.escape(Milestone::Any.title) }
 
   before(:all) do
     project.add_reporter(user)
@@ -811,6 +812,15 @@ describe API::Issues do
       expect(json_response.first['id']).to eq(confidential_issue.id)
     end
 
+    it 'returns an array of issues with any milestone' do
+      get api("#{base_url}/issues?milestone=#{any_milestone_title}", user)
+
+      response_ids = json_response.map { |issue| issue['id'] }
+
+      expect_paginated_array_response(size: 2)
+      expect(response_ids).to contain_exactly(closed_issue.id, issue.id)
+    end
+
     it 'sorts by created_at descending by default' do
       get api("#{base_url}/issues", user)