Add optional `search` param for Merge Requests API

changelogs/unreleased/38318-search-merge-requests-with-api.yml

+---
+title: Add optional search param for Merge Requests API
+merge_request:
+author:
+type: fixed

doc/api/merge_requests.md

@@ -47,6 +47,7 @@ Parameters:
 | `author_id`         | integer  | no       | Returns merge requests created by the given user `id`. Combine with `scope=all` or `scope=assigned-to-me`              |
 | `assignee_id`       | integer  | no       | Returns merge requests assigned to the given user `id`                                                                 |
 | `my_reaction_emoji` | string   | no       | Return merge requests reacted by the authenticated user by the given `emoji` _([Introduced][ce-14016] in GitLab 10.0)_ |
+| `search`            | string   | no       | Search merge requests against their `title` and `description`                                                          |
 
 ```json
 [
@@ -161,6 +162,7 @@ Parameters:
 | `author_id`         | integer        | no       | Returns merge requests created by the given user `id` _([Introduced][ce-13060] in GitLab 9.5)_                                 |
 | `assignee_id`       | integer        | no       | Returns merge requests assigned to the given user `id` _([Introduced][ce-13060] in GitLab 9.5)_                                |
 | `my_reaction_emoji` | string         | no       | Return merge requests reacted by the authenticated user by the given `emoji` _([Introduced][ce-14016] in GitLab 10.0)_         |
+| `search`            | string         | no       | Search merge requests against their `title` and `description`                                                                  |
 
 ```json
 [

lib/api/merge_requests.rb

@@ -41,6 +41,7 @@ module API
         optional :scope, type: String, values: %w[created-by-me assigned-to-me all],
                          desc: 'Return merge requests for the given scope: `created-by-me`, `assigned-to-me` or `all`'
         optional :my_reaction_emoji, type: String, desc: 'Return issues reacted by the authenticated user by the given emoji'
+        optional :search, type: String, desc: 'Search merge requests for text present in the title or description'
         use :pagination
       end
     end

spec/requests/api/merge_requests_spec.rb

@@ -150,6 +150,26 @@ describe API::MergeRequests do
         expect(json_response.length).to eq(1)
         expect(json_response.first['id']).to eq(merge_request3.id)
       end
+
+      context 'search params' do
+        before do
+          merge_request.update(title: 'Search title', description: 'Search description')
+        end
+
+        it 'returns merge requests matching given search string for title' do
+          get api("/merge_requests", user), search: merge_request.title
+
+          expect(json_response.length).to eq(1)
+          expect(json_response.first['id']).to eq(merge_request.id)
+        end
+
+        it 'returns merge requests for project matching given search string for description' do
+          get api("/merge_requests", user), project_id: project.id, search: merge_request.description
+
+          expect(json_response.length).to eq(1)
+          expect(json_response.first['id']).to eq(merge_request.id)
+        end
+      end
     end
   end