Feature/add language in repository to api

changelogs/unreleased/feature-add-language-in-repository-to-api.yml

+---
+title: 'API: add languages of project GET /projects/:id/languages'
+merge_request: 17770
+author: Roger Rüttimann
+type: added

doc/api/projects.md

@@ -915,6 +915,29 @@ Example response:
 }
 ```
+## Languages
+
+Get languages used in a project with percentage value.
+
+```
+GET /projects/:id/languages
+```
+
+```bash
+curl --header "PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK" "https://gitlab.example.com/api/v4/projects/5/languages"
+```
+
+Example response:
+
+```json
+{
+  "Ruby": 66.69,
+  "JavaScript": 22.98,
+  "HTML": 7.91,
+  "CoffeeScript": 2.42
+}
+```
+
 ## Archive a project
 Archives the project if the user is either admin or the project owner of this project. This action is

lib/api/projects.rb

@@ -338,6 +338,11 @@ module API
         end
       end
+      desc 'Get languages in project repository'
+      get ':id/languages' do
+        user_project.repository.languages.map { |language| language.values_at(:label, :value) }.to_h
+      end
+
       desc 'Remove a project'
       delete ":id" do
         authorize! :remove_project, user_project

spec/requests/api/projects_spec.rb

 # -*- coding: utf-8 -*-
 require 'spec_helper'
+shared_examples 'languages and percentages JSON response' do
+  let(:expected_languages) { project.repository.languages.map { |language| language.values_at(:label, :value)}.to_h }
+
+  it 'returns expected language values' do
+    get api("/projects/#{project.id}/languages", user)
+
+    expect(response).to have_gitlab_http_status(:ok)
+    expect(json_response).to eq(expected_languages)
+    expect(json_response.count).to be > 1
+  end
+end
+
 describe API::Projects do
   let(:user) { create(:user) }
   let(:user2) { create(:user) }
@@ -1694,6 +1706,42 @@ describe API::Projects do
     end
   end
+  describe 'GET /projects/:id/languages' do
+    context 'with an authorized user' do
+      it_behaves_like 'languages and percentages JSON response' do
+        let(:project) { project3 }
+      end
+
+      it 'returns not_found(404) for not existing project' do
+        get api("/projects/9999999999/languages", user)
+
+        expect(response).to have_gitlab_http_status(:not_found)
+      end
+    end
+
+    context 'with not authorized user' do
+      it 'returns not_found for existing but unauthorized project' do
+        get api("/projects/#{project3.id}/languages", user3)
+
+        expect(response).to have_gitlab_http_status(:not_found)
+      end
+    end
+
+    context 'without user' do
+      let(:project_public) { create(:project, :public, :repository) }
+
+      it_behaves_like 'languages and percentages JSON response' do
+        let(:project) { project_public }
+      end
+
+      it 'returns not_found for existing but unauthorized project' do
+        get api("/projects/#{project3.id}/languages", nil)
+
+        expect(response).to have_gitlab_http_status(:not_found)
+      end
+    end
+  end
+
   describe 'DELETE /projects/:id' do
     context 'when authenticated as user' do
       it 'removes project' do