Merge branch 'bvl-codeowners-file' into 'master'

Extract code owners from a CODEOWNERS file

Closes #6961

See merge request gitlab-org/gitlab-ee!6916

.gitlab/CODEOWNERS

+# Backend Maintainers are the default for all ruby files
+*.rb @ayufan @DouweM @dzaporozhets @grzesiek @nick.thomas @rspeicher @rymai @smcgivern
+*.rake @ayufan @DouweM @dzaporozhets @grzesiek @nick.thomas @rspeicher @rymai @smcgivern
+
+# Technical writing team are the default reviewers for everything in `doc/`
+/doc/ @axil @marcia
+
+# Frontend maintainers should see everything in `app/assets/`
+app/assets/ @annabeldunstone @ClemMakesApps @fatihacet @filipa @iamphill @mikegreiling @timzallmann
+
+# Someone from the database team should review changes in `db/`
+db/ @abrandl @NikolayS
+
+# Feature specific owners
+/ee/lib/gitlab/code_owners/ @reprazent

app/models/blob.rb

@@ -2,6 +2,8 @@
 
 # Blob is a Rails-specific wrapper around Gitlab::Git::Blob objects
 class Blob < SimpleDelegator
+  prepend EE::Blob
+
   CACHE_TIME = 60 # Cache raw blobs referred to by a (mutable) ref for 1 minute
   CACHE_TIME_IMMUTABLE = 3600 # Cache blobs referred to by an immutable reference for 1 hour
 

app/models/concerns/case_sensitivity.rb

@@ -10,22 +10,45 @@ module CaseSensitivity
     # Unlike other ActiveRecord methods this method only operates on a Hash.
     def iwhere(params)
       criteria = self
-      cast_lower = Gitlab::Database.postgresql?
 
       params.each do |key, value|
-        column = ActiveRecord::Base.connection.quote_table_name(key)
-
-        condition =
-          if cast_lower
-            "LOWER(#{column}) = LOWER(:value)"
+        criteria = case value
+                   when Array
+                     criteria.where(value_in(key, value))
                    else
-            "#{column} = :value"
+                     criteria.where(value_equal(key, value))
                    end
-
-        criteria = criteria.where(condition, value: value)
       end
 
       criteria
     end
+
+    private
+
+    def value_equal(column, value)
+      lower_value = lower_value(value)
+
+      lower_column(arel_table[column]).eq(lower_value).to_sql
+    end
+
+    def value_in(column, values)
+      lower_values = values.map do |value|
+        lower_value(value)
+      end
+
+      lower_column(arel_table[column]).in(lower_values).to_sql
+    end
+
+    def lower_value(value)
+      return value if Gitlab::Database.mysql?
+
+      Arel::Nodes::NamedFunction.new('LOWER', [Arel::Nodes.build_quoted(value)])
+    end
+
+    def lower_column(column)
+      return column if Gitlab::Database.mysql?
+
+      column.lower
+    end
   end
 end

app/models/user.rb

@@ -266,6 +266,7 @@ class User < ActiveRecord::Base
   scope :order_recent_sign_in, -> { reorder(Gitlab::Database.nulls_last_order('current_sign_in_at', 'DESC')) }
   scope :order_oldest_sign_in, -> { reorder(Gitlab::Database.nulls_last_order('current_sign_in_at', 'ASC')) }
   scope :confirmed, -> { where.not(confirmed_at: nil) }
+  scope :by_username, -> (usernames) { iwhere(username: usernames) }
 
   # Limits the users to those that have TODOs, optionally in the given state.
   #
@@ -457,11 +458,11 @@ class User < ActiveRecord::Base
     end
 
     def find_by_username(username)
-      iwhere(username: username).take
+      by_username(username).take
     end
 
     def find_by_username!(username)
-      iwhere(username: username).take!
+      by_username(username).take!
     end
 
     def find_by_personal_access_token(token_string)

app/views/projects/blob/_blob.html.haml

@@ -4,7 +4,7 @@
   .well-segment
     %ul.blob-commit-info
       = render 'projects/commits/commit', commit: @last_commit, project: @project, ref: @ref
-
+  = render_if_exists 'projects/blob/owners', blob: blob
   = render "projects/blob/auxiliary_viewer", blob: blob
 
 #blob-content-holder.blob-content-holder

doc/user/project/code_owners.md

+# Code owners
+
+> [Introduced](https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/6916)
+in [Gitlab Starter](https://about.gitlab.com/pricing/) 11.3.
+
+You can use a `CODEOWNERS` file to specify users that are responsible
+for certain files in a repository.
+
+You can choose and add the `CODEOWNERS` file in three places:
+
+- to the root directory of the repository
+- inside the `.gitlab/` directory
+- inside the `docs/` directory
+
+The `CODEOWNERS` file is scoped to a branch, which means that with the
+introduction of new files, the person adding the new content can
+specify themselves as a code owner, all before the new changes
+get merged to the default branch.
+
+When a file matches multiple entries in the `CODEOWNERS` file,
+the users from all entries are displayed on the blob page of
+the given file.
+
+## The syntax of a code owners file
+
+Files can be specified using the same kind of patterns you would use
+in the `.gitignore` file followed by the `@username` or email of one
+or more users that should be owners of the file.
+
+The order in which the paths are defined is significant: the last
+pattern that matches a given path will be used to find the code
+owners.
+
+Starting a line with a `#` indicates a comment. This needs to be
+escaped using `\#` to address files for which the name starts with a
+`#`.
+
+Example `CODEOWNERS` file:
+
+```
+# This is an example code owners file, lines starting with a `#` will
+# be ignored.
+
+# app/ @commented-rule
+
+# We can specifiy a default match using wildcards:
+* @default-codeowner
+
+# Rules defined later in the file take precedence over the rules
+# defined before.
+# This will match all files for which the file name ends in `.rb`
+*.rb @ruby-owner
+
+# Files with a `#` can still be accesssed by escaping the pound sign
+\#file_with_pound.rb @owner-file-with-pound
+
+# Multiple codeowners can be specified, separated by whitespace
+CODEOWNERS @multiple @owners	@tab-separated
+
+# Both usernames or email addresses can be used to match
+# users. Everything else will be ignored. For example this will
+# specify `@legal` and a user with email `janedoe@gitlab.com` as the
+# owner for the LICENSE file
+LICENSE @legal this_does_not_match janedoe@gitlab.com
+
+# Ending a path in a `/` will specify the code owners for every file
+# nested in that directory, on any level
+/docs/ @all-docs
+
+# Ending a path in `/*` will specify code owners for every file in
+# that directory, but not nested deeper. This will match
+# `docs/index.md` but not `docs/projects/index.md`
+/docs/* @root-docs
+
+# This will make a `lib` directory nested anywhere in the repository
+# match
+lib/ @lib-owner
+
+# This will only match a `config` directory in the root of the
+# repository
+/config/ @config-owner
+
+# If the path contains spaces, these need to be escaped like this:
+path\ with\ spaces/ @space-owner
+```

doc/user/project/index.md

@@ -87,6 +87,7 @@ website with GitLab Pages
 your code blocks, overriding GitLab's default choice of language
 - [Badges](badges.md): Badges for the project overview
 - [Maven packages](maven_packages.md): Your private Maven repository in GitLab
+- [Code owners](code_owners.md): Specify code owners for certain files **[STARTER]**
 
 ### Project's integrations
 

ee/app/helpers/ee/users_helper.rb

+# frozen_string_literal: true
+
+module EE
+  module UsersHelper
+    def users_sentence(users, link_class: nil)
+      users.map { |user| link_to(user.name, user, class: link_class) }.to_sentence.html_safe
+    end
+  end
+end

ee/app/models/ee/blob.rb

+# frozen_string_literal: true
+
+module EE
+  module Blob
+    extend ActiveSupport::Concern
+
+    def owners
+      @owners ||= ::Gitlab::CodeOwners.for_blob(self)
+    end
+  end
+end

ee/app/models/ee/repository.rb

@@ -87,5 +87,10 @@ module EE
     def geo_updated_event_source
       is_wiki ? Geo::RepositoryUpdatedEvent::WIKI : Geo::RepositoryUpdatedEvent::REPOSITORY
     end
+
+    def code_owners_blob(ref: 'HEAD')
+      possible_code_owner_blobs = ::Gitlab::CodeOwners::FILE_PATHS.map { |path| [ref, path] }
+      blobs_at(possible_code_owner_blobs).compact.first
+    end
   end
 end

ee/app/models/license.rb

@@ -9,6 +9,7 @@ class License < ActiveRecord::Base
   EES_FEATURES = %i[
     audit_events
     burndown_charts
+    code_owners
     contribution_analytics
     elastic_search
     export_issues

ee/app/views/projects/blob/_owners.html.haml

+- return if blob.owners.empty?
+
+.well-segment.blob-auxiliary-viewer.file-owner-content
+  = sprite_icon('users', size: 18, css_class: 'icon')
+  %strong
+    = _("Code owners")
+  = link_to icon('question-circle'), help_page_path('user/project/code_owners'), title: 'About this feature', target: '_blank'
+  :
+  = users_sentence(blob.owners, link_class: 'file-owner-link')

ee/changelogs/unreleased/bvl-codeowners-file.yml

+---
+title: Allow specifying code owners in a CODEOWNERS file
+merge_request: 6916
+author:
+type: added

ee/lib/gitlab/code_owners.rb

+# frozen_string_literal: true
+
+module Gitlab
+  module CodeOwners
+    FILE_NAME = 'CODEOWNERS'
+    FILE_PATHS = [FILE_NAME, "docs/#{FILE_NAME}", ".gitlab/#{FILE_NAME}"].freeze
+
+    def self.for_blob(blob)
+      if blob.project.feature_available?(:code_owners)
+        Loader.new(blob.project, blob.commit_id, blob.path).users
+      else
+        User.none
+      end
+    end
+  end
+end

ee/lib/gitlab/code_owners/file.rb

+# frozen_string_literal: true
+
+module Gitlab
+  module CodeOwners
+    class File
+      def initialize(blob)
+        @blob = blob
+      end
+
+      def parsed_data
+        @parsed_data ||= get_parsed_data
+      end
+
+      def empty?
+        parsed_data.empty?
+      end
+
+      def owners_for_path(path)
+        matching_pattern = parsed_data.keys.reverse.detect do |pattern|
+          path_matches?(pattern, path)
+        end
+
+        parsed_data[matching_pattern]
+      end
+
+      private
+
+      def data
+        if @blob && !@blob.binary?
+          @blob.data
+        else
+          ""
+        end
+      end
+
+      def get_parsed_data
+        parsed = {}
+
+        data.lines.each do |line|
+          line = line.strip
+          next unless line.present?
+          next if line.starts_with?('#')
+
+          pattern, _separator, owners = line.partition(/(?<!\\)\s+/)
+
+          pattern = normalize_pattern(pattern)
+
+          parsed[pattern] = owners
+        end
+
+        parsed
+      end
+
+      def normalize_pattern(pattern)
+        # Remove `\` when escaping `\#`
+        pattern = pattern.sub(/\A\\#/, '#')
+        # Replace all whitespace preceded by a \ with a regular whitespace
+        pattern = pattern.gsub(/\\\s+/, ' ')
+
+        if pattern.starts_with?('/')
+          # Remove the leading slash when only matching root directory as the
+          # paths that we will be matching will always be passed in starting
+          # from the root of the repsitory.
+          pattern = pattern.sub(%r{\A/}, '')
+        elsif !pattern.starts_with?('*')
+          # If the pattern is a regular match, prepend it with ** so we match
+          # nested in every directory
+          pattern = "**#{pattern}"
+        end
+
+        pattern
+      end
+
+      def path_matches?(pattern, path)
+        flags = ::File::FNM_DOTMATCH
+
+        if pattern.ends_with?('/*')
+          # Then the pattern ends in a wildcard, we only want to go one level deep
+          # setting `::File::FNM_PATHNAME` makes the `*` not match directory
+          # separators
+          flags |= ::File::FNM_PATHNAME
+          ::File.fnmatch?(pattern, path, flags)
+        else
+          # Replace a pattern ending with `/` to `/*` to match everything within
+          # that directory
+          nested_pattern = pattern.sub(%r{/\z}, '/*')
+          ::File.fnmatch?(nested_pattern, path, flags)
+        end
+      end
+    end
+  end
+end

ee/lib/gitlab/code_owners/loader.rb

+# frozen_string_literal: true
+
+module Gitlab
+  module CodeOwners
+    class Loader
+      def initialize(project, ref, path)
+        @project, @ref, @path = project, ref, path
+      end
+
+      def users
+        return User.none if code_owners_file.empty?
+
+        owners = code_owners_file.owners_for_path(@path)
+        extracted_users = Gitlab::UserExtractor.new(owners).users
+
+        @project.authorized_users.merge(extracted_users)
+      end
+
+      private
+
+      def code_owners_file
+        if RequestStore.active?
+          RequestStore.fetch("project-#{@project.id}:code-owners:#{@ref}") do
+            load_code_owners_file
+          end
+        else
+          load_code_owners_file
+        end
+      end
+
+      def load_code_owners_file
+        code_owners_blob = @project.repository.code_owners_blob(ref: @ref)
+        Gitlab::CodeOwners::File.new(code_owners_blob)
+      end
+    end
+  end
+end

ee/spec/features/projects/view_blob_with_code_owners_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe 'File blob > Code owners', :js do
+  let(:project) { create(:project, :private, :repository) }
+  let(:user) { project.owner }
+  let(:code_owner) { create(:user, username: 'documentation-owner') }
+
+  before do
+    sign_in(user)
+    project.add_developer(code_owner)
+  end
+
+  def visit_blob(path, anchor: nil, ref: 'master')
+    visit project_blob_path(project, File.join(ref, path), anchor: anchor)
+
+    wait_for_requests
+  end
+
+  context 'when there is a codeowners file' do
+    context 'when the feature is available' do
+      before do
+        stub_licensed_features(code_owners: true)
+      end
+
+      it 'shows the code owners related to a file' do
+        visit_blob('docs/CODEOWNERS', ref: 'with-codeowners')
+
+        within('.file-owner-content') do
+          expect(page).to have_content('Code owners')
+          expect(page).to have_link(code_owner.name)
+        end
+      end
+
+      it 'does not show the code owners banner when there are no code owners' do
+        visit_blob('README.md')
+
+        expect(page).not_to have_content('Code owners:')
+      end
+    end
+
+    context 'when the feature is not available' do
+      before do
+        stub_licensed_features(code_owners: false)
+      end
+
+      it 'does not show the code owners related to a file' do
+        visit_blob('docs/CODEOWNERS', ref: 'with-codeowners')
+
+        expect(page).not_to have_content('Code owners')
+      end
+    end
+  end
+end

ee/spec/fixtures/codeowners_example

+# This is an example code owners file, lines starting with a `#` will
+# be ignored.
+
+# app/ @commented-rule
+
+# We can specifiy a default match using wildcards:
+* @default-codeowner
+
+# Rules defined later in the file take precedence over the rules
+# defined before.
+# This will match all files for which the file name ends in `.rb`
+*.rb @ruby-owner
+
+# Files with a `#` can still be accesssed by escaping the pound sign
+\#file_with_pound.rb @owner-file-with-pound
+
+# Multiple codeowners can be specified, separated by whitespace
+CODEOWNERS @multiple @owners	@tab-separated
+
+# Both usernames or email addresses can be used to match
+# users. Everything else will be ignored. For example this will
+# specify `@legal` and a user with email `janedoe@gitlab.com` as the
+# owner for the LICENSE file
+LICENSE @legal this does not match janedoe@gitlab.com
+
+# Ending a path in a `/` will specify the code owners for every file
+# nested in that directory, on any level
+/docs/ @all-docs
+
+# Ending a path in `/*` will specify code owners for every file in
+# that directory, but not nested deeper. This will match
+# `docs/index.md` but not `docs/projects/index.md`
+/docs/* @root-docs
+
+# This will make a `lib` directory nested anywhere in the repository
+# match
+lib/ @lib-owner
+
+# This will only match a `config` directory in the root of the
+# repository
+/config/ @config-owner
+
+# If the path contains spaces, these need to be escaped like this:
+path\ with\ spaces/ @space-owner

ee/spec/lib/gitlab/code_owners/file_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe Gitlab::CodeOwners::File do
+  include FakeBlobHelpers
+
+  let(:project) { build(:project) }
+  let(:file_content) do
+    File.read(Rails.root.join('ee', 'spec', 'fixtures', 'codeowners_example'))
+  end
+
+  let(:blob) { fake_blob(path: 'CODEOWNERS', data: file_content) }
+
+  subject(:file) { described_class.new(blob) }
+
+  describe '#parsed_data' do
+    it 'parses all the required lines' do
+      expected_patterns = [
+        '*', '**#file_with_pound.rb', '*.rb', '**CODEOWNERS', '**LICENSE', 'docs/',
+        'docs/*', 'config/', '**lib/', '**path with spaces/'
+      ]
+      expect(file.parsed_data.keys)
+        .to contain_exactly(*expected_patterns)
+    end
+
+    it 'allows usernames and emails' do
+      expect(file.parsed_data['**LICENSE']).to include('legal', 'janedoe@gitlab.com')
+    end
+
+    context 'when there are entries that do not look like user references' do
+      let(:file_content) do
+        "a-path/ this is all random @username and email@gitlab.org"
+      end
+
+      it 'ignores the entries' do
+        expect(file.parsed_data['**a-path/']).to include('username', 'email@gitlab.org')
+      end
+    end
+  end
+
+  describe '#empty?' do
+    subject { file.empty? }
+
+    it { is_expected.to be(false) }
+
+    context 'when there is no content' do
+      let(:file_content) { "" }
+
+      it { is_expected.to be(true) }
+    end
+
+    context 'when the file is binary' do
+      let(:blob) { fake_blob(binary: true) }
+
+      it { is_expected.to be(true) }
+    end
+
+    context 'when the file did not exist' do
+      let(:blob) { nil }
+
+      it { is_expected.to be(true) }
+    end
+  end
+
+  describe '#owners_for_path' do
+    context 'for a path without matches' do
+      let(:file_content) do
+        <<~CONTENT
+        # Simulating a CODOWNERS without entries
+        CONTENT
+      end
+
+      it 'returns an nil for an unmatched path' do
+        owners = file.owners_for_path('no_matches')
+
+        expect(owners).to be_nil
+      end
+    end
+
+    it 'matches random files to a pattern' do
+      owners = file.owners_for_path('app/assets/something.vue')
+
+      expect(owners).to include('default-codeowner')
+    end
+
+    it 'uses the last pattern if multiple patterns match' do
+      owners = file.owners_for_path('hello.rb')
+
+      expect(owners).to eq('@ruby-owner')
+    end
+
+    it 'returns the usernames for a file matching a pattern with a glob' do
+      owners = file.owners_for_path('app/models/repository.rb')
+
+      expect(owners).to eq('@ruby-owner')
+    end
+
+    it 'allows specifying multiple users' do
+      owners = file.owners_for_path('CODEOWNERS')
+
+      expect(owners).to include('multiple', 'owners', 'tab-separated')
+    end
+
+    it 'returns emails and usernames for a matched pattern' do
+      owners = file.owners_for_path('LICENSE')
+
+      expect(owners).to include('legal', 'janedoe@gitlab.com')
+    end
+
+    it 'allows escaping the pound sign used for comments' do
+      owners = file.owners_for_path('examples/#file_with_pound.rb')
+
+      expect(owners).to include('owner-file-with-pound')
+    end
+
+    it 'returns the usernames for a file nested in a directory' do
+      owners = file.owners_for_path('docs/projects/index.md')
+
+      expect(owners).to include('all-docs')
+    end
+
+    it 'returns the usernames for a pattern matched with a glob in a folder' do
+      owners = file.owners_for_path('docs/index.md')
+
+      expect(owners).to include('root-docs')
+    end
+
+    it 'allows matching files nested anywhere in the repository', :aggregate_failures do
+      lib_owners = file.owners_for_path('lib/gitlab/git/repository.rb')
+      other_lib_owners = file.owners_for_path('ee/lib/gitlab/git/repository.rb')
+
+      expect(lib_owners).to include('lib-owner')
+      expect(other_lib_owners).to include('lib-owner')
+    end
+
+    it 'allows allows limiting the matching files to the root of the repository', :aggregate_failures do
+      config_owners = file.owners_for_path('config/database.yml')
+      other_config_owners = file.owners_for_path('other/config/database.yml')
+
+      expect(config_owners).to include('config-owner')
+      expect(other_config_owners).to eq('@default-codeowner')
+    end
+
+    it 'correctly matches paths with spaces' do
+      owners = file.owners_for_path('path with spaces/README.md')
+
+      expect(owners).to eq('@space-owner')
+    end
+
+    context 'paths with whitespaces and username lookalikes' do
+      let(:file_content) do
+        'a/weird\ path\ with/\ @username\ /\ and-email@lookalikes.com\ / @user-1 email@gitlab.org @user-2'
+      end
+
+      it 'parses correctly' do
+        owners = file.owners_for_path('a/weird path with/ @username / and-email@lookalikes.com /test.rb')
+
+        expect(owners).to include('user-1', 'user-2', 'email@gitlab.org')
+        expect(owners).not_to include('username', 'and-email@lookalikes.com')
+      end
+    end
+  end
+end

ee/spec/lib/gitlab/code_owners/loader_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe Gitlab::CodeOwners::Loader do
+  include FakeBlobHelpers
+  set(:group) { create(:group) }
+  set(:project) { create(:project, namespace: group) }
+  subject(:loader) { described_class.new(project, 'with-codeowners', path) }
+
+  let!(:owner_1) { create(:user, username: 'owner-1') }
+  let!(:email_owner) { create(:user, username: 'owner-2') }
+  let!(:owner_3) { create(:user, username: 'owner-3') }
+  let!(:documentation_owner) { create(:user, username: 'documentation-owner') }
+  let(:codeowner_content) do
+    <<~CODEOWNERS
+    docs/* @documentation-owner
+    docs/CODEOWNERS @owner-1 owner2@gitlab.org @owner-3 @documentation-owner
+    CODEOWNERS
+  end
+  let(:codeowner_blob) { fake_blob(path: 'CODEOWNERS', data: codeowner_content) }
+  let(:path) { 'docs/CODEOWNERS' }
+
+  before do
+    create(:email, user: email_owner, email: 'owner2@gitlab.org')
+    project.add_developer(owner_1)
+    project.add_developer(email_owner)
+    project.add_developer(documentation_owner)
+
+    allow(project.repository).to receive(:code_owners_blob).and_return(codeowner_blob)
+  end
+
+  describe '#users' do
+    context 'with a CODEOWNERS file' do
+      context 'for a path with code owners' do
+        it 'returns all existing users that are members of the project' do
+          expect(loader.users).to contain_exactly(owner_1, email_owner, documentation_owner)
+        end
+
+        it 'does not return users that are not members of the project' do
+          expect(loader.users).not_to include(owner_3)
+        end
+
+        it 'includes group members of the project' do
+          group.add_developer(owner_3)
+
+          expect(loader.users).to include(owner_3)
+        end
+      end
+
+      context 'for another path' do
+        let(:path) { 'no-codeowner' }
+
+        it 'returns no users' do
+          expect(loader.users).to be_empty
+        end
+      end
+    end
+
+    context 'when there is no codeowners file' do
+      let(:codeowner_blob) { nil }
+
+      it 'returns no users without failing' do
+        expect(loader.users).to be_empty
+      end
+    end
+
+    context 'with the request store', :request_store do
+      it 'only calls out to the repository once' do
+        expect(project.repository).to receive(:code_owners_blob).once
+
+        2.times { loader.users }
+      end
+
+      it 'only processes the file once' do
+        code_owners_file = loader.__send__(:code_owners_file)
+
+        expect(code_owners_file).to receive(:get_parsed_data).once.and_call_original
+
+        2.times { loader.users }
+      end
+    end
+  end
+end

ee/spec/lib/gitlab/code_owners_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe Gitlab::CodeOwners do
+  include FakeBlobHelpers
+
+  let!(:code_owner) { create(:user, username: 'owner-1') }
+  let(:project) { create(:project, :repository) }
+  let(:blob) do
+    project.repository.blob_at(TestEnv::BRANCH_SHA['with-codeowners'], 'docs/CODEOWNERS')
+  end
+  let(:codeowner_content) { "docs/CODEOWNERS @owner-1" }
+  let(:codeowner_blob) { fake_blob(path: 'CODEOWNERS', data: codeowner_content) }
+
+  before do
+    project.add_developer(code_owner)
+    allow(project.repository).to receive(:code_owners_blob).and_return(codeowner_blob)
+  end
+
+  describe '.for_blob' do
+    context 'when the feature is available' do
+      before do
+        stub_licensed_features(code_owners: true)
+      end
+
+      it 'returns users for a blob' do
+        expect(described_class.for_blob(blob)).to include(code_owner)
+      end
+    end
+
+    context 'when the feature is not available' do
+      before do
+        stub_licensed_features(code_owners: false)
+      end
+
+      it 'returns no users' do
+        expect(described_class.for_blob(blob)).to be_empty
+      end
+    end
+  end
+end

ee/spec/models/blob_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe Blob do
+  let(:project) { create(:project, :repository) }
+  let(:blob) do
+    project.repository.blob_at(TestEnv::BRANCH_SHA['with-codeowners'], 'docs/CODEOWNERS')
+  end
+  let(:code_owner) { create(:user, username: 'documentation-owner') }
+
+  before do
+    project.add_developer(code_owner)
+  end
+
+  describe '#owners' do
+    context 'when the feature is available' do
+      before do
+        stub_licensed_features(code_owners: true)
+      end
+
+      it 'returns the owners from the file' do
+        expect(blob.owners).to include(code_owner)
+      end
+    end
+
+    context 'when the feature is not available' do
+      before do
+        stub_licensed_features(code_owners: false)
+      end
+
+      it 'returns no code owners' do
+        expect(blob.owners).to be_empty
+      end
+    end
+  end
+end

ee/spec/models/repository_spec.rb

@@ -154,4 +154,24 @@ describe Repository do
       end
     end
   end
+
+  describe '#code_owners_blob' do
+    it 'returns nil if there is no codeowners file' do
+      expect(repository.code_owners_blob(ref: 'master')).to be_nil
+    end
+
+    it 'returns the content of the codeowners file when it is found' do
+      expect(repository.code_owners_blob(ref: 'with-codeowners').data).to include('example CODEOWNERS file')
+    end
+
+    it 'requests the CODOWNER blobs in batch in the correct order' do
+      expect(repository).to receive(:blobs_at)
+                              .with([%w(HEAD CODEOWNERS),
+                                     %w(HEAD docs/CODEOWNERS),
+                                     %w(HEAD .gitlab/CODEOWNERS)])
+                              .and_call_original
+
+      repository.code_owners_blob
+    end
+  end
 end

lib/gitlab/user_extractor.rb

+# frozen_string_literal: true
+
+# This class extracts all users found in a piece of text by the username or the
+# email adress
+
+module Gitlab
+  class UserExtractor
+    # Not using `Devise.email_regexp` to filter out any chars that an email
+    # does not end with and not pinning the email to a start of end of a string.
+    EMAIL_REGEXP = /(?<email>([^@\s]+@[^@\s]+(?<!\W)))/
+    USERNAME_REGEXP = User.reference_pattern
+
+    def initialize(text)
+      @text = text
+    end
+
+    def users
+      return User.none unless @text.present?
+
+      @users ||= User.from("(#{union.to_sql}) users")
+    end
+
+    def usernames
+      matches[:usernames]
+    end
+
+    def emails
+      matches[:emails]
+    end
+
+    def references
+      @references ||= matches.values.flatten
+    end
+
+    def matches
+      @matches ||= {
+        emails: @text.scan(EMAIL_REGEXP).flatten.uniq,
+        usernames: @text.scan(USERNAME_REGEXP).flatten.uniq
+      }
+    end
+
+    private
+
+    def union
+      relations = []
+
+      relations << User.by_any_email(emails) if emails.any?
+      relations << User.by_username(usernames) if usernames.any?
+
+      Gitlab::SQL::Union.new(relations)
+    end
+  end
+end

locale/gitlab.pot

@@ -1979,6 +1979,9 @@ msgstr ""
 msgid "ClusterIntegration|sign up"
 msgstr ""
 
+msgid "Code owners"
+msgstr ""
+
 msgid "Cohorts"
 msgstr ""
 

spec/lib/gitlab/user_extractor_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe Gitlab::UserExtractor do
+  let(:text) do
+    <<~TXT
+    This is a long texth that mentions some users.
+    @user-1, @user-2 and user@gitlab.org take a walk in the park.
+    There they meet @user-4 that was out with other-user@gitlab.org.
+    @user-1 thought it was late, so went home straight away
+    TXT
+  end
+  subject(:extractor) { described_class.new(text) }
+
+  describe '#users' do
+    it 'returns an empty relation when nil was passed' do
+      extractor = described_class.new(nil)
+
+      expect(extractor.users).to be_empty
+      expect(extractor.users).to be_a(ActiveRecord::Relation)
+    end
+
+    it 'returns the user case insensitive for usernames' do
+      user = create(:user, username: "USER-4")
+
+      expect(extractor.users).to include(user)
+    end
+
+    it 'returns users by primary email' do
+      user = create(:user, email: 'user@gitlab.org')
+
+      expect(extractor.users).to include(user)
+    end
+
+    it 'returns users by secondary email' do
+      user = create(:email, email: 'other-user@gitlab.org').user
+
+      expect(extractor.users).to include(user)
+    end
+  end
+
+  describe '#matches' do
+    it 'includes all mentioned email adresses' do
+      expect(extractor.matches[:emails]).to contain_exactly('user@gitlab.org', 'other-user@gitlab.org')
+    end
+
+    it 'includes all mentioned usernames' do
+      expect(extractor.matches[:usernames]).to contain_exactly('user-1', 'user-2', 'user-4')
+    end
+  end
+
+  describe '#references' do
+    it 'includes all user-references once' do
+      expect(extractor.references).to contain_exactly('user-1', 'user-2', 'user@gitlab.org', 'user-4', 'other-user@gitlab.org')
+    end
+  end
+end

spec/models/concerns/case_sensitivity_spec.rb

@@ -3,186 +3,50 @@ require 'spec_helper'
 describe CaseSensitivity do
   describe '.iwhere' do
     let(:connection) { ActiveRecord::Base.connection }
-    let(:model)      { Class.new { include CaseSensitivity } }
-
-    describe 'using PostgreSQL' do
-      before do
-        allow(Gitlab::Database).to receive(:postgresql?).and_return(true)
-        allow(Gitlab::Database).to receive(:mysql?).and_return(false)
+    let(:model) do
+      Class.new(ActiveRecord::Base) do
+        include CaseSensitivity
+        self.table_name = 'namespaces'
       end
-
-      describe 'with a single column/value pair' do
-        it 'returns the criteria for a column and a value' do
-          criteria = double(:criteria)
-
-          expect(connection).to receive(:quote_table_name)
-            .with(:foo)
-            .and_return('"foo"')
-
-          expect(model).to receive(:where)
-            .with(%q{LOWER("foo") = LOWER(:value)}, value: 'bar')
-            .and_return(criteria)
-
-          expect(model.iwhere(foo: 'bar')).to eq(criteria)
     end
 
-        it 'returns the criteria for a column with a table, and a value' do
-          criteria = double(:criteria)
-
-          expect(connection).to receive(:quote_table_name)
-            .with(:'foo.bar')
-            .and_return('"foo"."bar"')
+    let!(:model_1) { model.create(path: 'mOdEl-1', name: 'mOdEl 1') }
+    let!(:model_2) { model.create(path: 'mOdEl-2', name: 'mOdEl 2') }
 
-          expect(model).to receive(:where)
-            .with(%q{LOWER("foo"."bar") = LOWER(:value)}, value: 'bar')
-            .and_return(criteria)
-
-          expect(model.iwhere('foo.bar'.to_sym => 'bar')).to eq(criteria)
-        end
+    it 'finds a single instance by a single attribute regardless of case' do
+      expect(model.iwhere(path: 'MODEL-1')).to contain_exactly(model_1)
     end
 
-      describe 'with multiple column/value pairs' do
-        it 'returns the criteria for a column and a value' do
-          initial = double(:criteria)
-          final   = double(:criteria)
-
-          expect(connection).to receive(:quote_table_name)
-            .with(:foo)
-            .and_return('"foo"')
-
-          expect(connection).to receive(:quote_table_name)
-            .with(:bar)
-            .and_return('"bar"')
-
-          expect(model).to receive(:where)
-            .with(%q{LOWER("foo") = LOWER(:value)}, value: 'bar')
-            .and_return(initial)
-
-          expect(initial).to receive(:where)
-            .with(%q{LOWER("bar") = LOWER(:value)}, value: 'baz')
-            .and_return(final)
-
-          got = model.iwhere(foo: 'bar', bar: 'baz')
-
-          expect(got).to eq(final)
+    it 'finds multiple instances by a single attribute regardless of case' do
+      expect(model.iwhere(path: %w(MODEL-1 model-2))).to contain_exactly(model_1, model_2)
     end
 
-        it 'returns the criteria for a column with a table, and a value' do
-          initial = double(:criteria)
-          final   = double(:criteria)
-
-          expect(connection).to receive(:quote_table_name)
-            .with(:'foo.bar')
-            .and_return('"foo"."bar"')
-
-          expect(connection).to receive(:quote_table_name)
-            .with(:'foo.baz')
-            .and_return('"foo"."baz"')
-
-          expect(model).to receive(:where)
-            .with(%q{LOWER("foo"."bar") = LOWER(:value)}, value: 'bar')
-            .and_return(initial)
-
-          expect(initial).to receive(:where)
-            .with(%q{LOWER("foo"."baz") = LOWER(:value)}, value: 'baz')
-            .and_return(final)
-
-          got = model.iwhere('foo.bar'.to_sym => 'bar',
-                             'foo.baz'.to_sym => 'baz')
-
-          expect(got).to eq(final)
-        end
-      end
+    it 'finds instances by multiple attributes' do
+      expect(model.iwhere(path: %w(MODEL-1 model-2), name: 'model 1'))
+        .to contain_exactly(model_1)
     end
 
-    describe 'using MySQL' do
-      before do
-        allow(Gitlab::Database).to receive(:postgresql?).and_return(false)
-        allow(Gitlab::Database).to receive(:mysql?).and_return(true)
-      end
+    # Using `mysql` & `postgresql` metadata-tags here because both adapters build
+    # the query slightly differently
+    context 'for MySQL', :mysql do
+      it 'builds a simple query' do
+        query = model.iwhere(path: %w(MODEL-1 model-2), name: 'model 1').to_sql
+        expected_query = <<~QRY.strip
+        SELECT `namespaces`.* FROM `namespaces` WHERE (`namespaces`.`path` IN ('MODEL-1', 'model-2')) AND (`namespaces`.`name` = 'model 1')
+        QRY
 
-      describe 'with a single column/value pair' do
-        it 'returns the criteria for a column and a value' do
-          criteria = double(:criteria)
-
-          expect(connection).to receive(:quote_table_name)
-            .with(:foo)
-            .and_return('`foo`')
-
-          expect(model).to receive(:where)
-            .with(%q{`foo` = :value}, value: 'bar')
-            .and_return(criteria)
-
-          expect(model.iwhere(foo: 'bar')).to eq(criteria)
+        expect(query).to eq(expected_query)
       end
-
-        it 'returns the criteria for a column with a table, and a value' do
-          criteria = double(:criteria)
-
-          expect(connection).to receive(:quote_table_name)
-            .with(:'foo.bar')
-            .and_return('`foo`.`bar`')
-
-          expect(model).to receive(:where)
-            .with(%q{`foo`.`bar` = :value}, value: 'bar')
-            .and_return(criteria)
-
-          expect(model.iwhere('foo.bar'.to_sym => 'bar'))
-            .to eq(criteria)
-        end
-      end
-
-      describe 'with multiple column/value pairs' do
-        it 'returns the criteria for a column and a value' do
-          initial = double(:criteria)
-          final   = double(:criteria)
-
-          expect(connection).to receive(:quote_table_name)
-            .with(:foo)
-            .and_return('`foo`')
-
-          expect(connection).to receive(:quote_table_name)
-            .with(:bar)
-            .and_return('`bar`')
-
-          expect(model).to receive(:where)
-            .with(%q{`foo` = :value}, value: 'bar')
-            .and_return(initial)
-
-          expect(initial).to receive(:where)
-            .with(%q{`bar` = :value}, value: 'baz')
-            .and_return(final)
-
-          got = model.iwhere(foo: 'bar', bar: 'baz')
-
-          expect(got).to eq(final)
     end
 
-        it 'returns the criteria for a column with a table, and a value' do
-          initial = double(:criteria)
-          final   = double(:criteria)
-
-          expect(connection).to receive(:quote_table_name)
-            .with(:'foo.bar')
-            .and_return('`foo`.`bar`')
+    context 'for PostgreSQL', :postgresql do
+      it 'builds a query using LOWER' do
+        query = model.iwhere(path: %w(MODEL-1 model-2), name: 'model 1').to_sql
+        expected_query = <<~QRY.strip
+        SELECT \"namespaces\".* FROM \"namespaces\" WHERE (LOWER(\"namespaces\".\"path\") IN (LOWER('MODEL-1'), LOWER('model-2'))) AND (LOWER(\"namespaces\".\"name\") = LOWER('model 1'))
+        QRY
 
-          expect(connection).to receive(:quote_table_name)
-            .with(:'foo.baz')
-            .and_return('`foo`.`baz`')
-
-          expect(model).to receive(:where)
-            .with(%q{`foo`.`bar` = :value}, value: 'bar')
-            .and_return(initial)
-
-          expect(initial).to receive(:where)
-            .with(%q{`foo`.`baz` = :value}, value: 'baz')
-            .and_return(final)
-
-          got = model.iwhere('foo.bar'.to_sym => 'bar',
-                             'foo.baz'.to_sym => 'baz')
-
-          expect(got).to eq(final)
-        end
+        expect(query).to eq(expected_query)
       end
     end
   end

spec/models/user_spec.rb

@@ -433,6 +433,23 @@ describe User do
         end
       end
     end
+
+    describe '.by_username' do
+      it 'finds users regardless of the case passed' do
+        user = create(:user, username: 'CaMeLcAsEd')
+        user2 = create(:user, username: 'UPPERCASE')
+
+        expect(described_class.by_username(%w(CAMELCASED uppercase)))
+          .to contain_exactly(user, user2)
+      end
+
+      it 'finds a single user regardless of the case passed' do
+        user = create(:user, username: 'CaMeLcAsEd')
+
+        expect(described_class.by_username('CAMELCASED'))
+          .to contain_exactly(user)
+      end
+    end
   end
 
   describe "Respond to" do

spec/support/helpers/test_env.rb

@@ -52,7 +52,8 @@ module TestEnv
     'add_images_and_changes'             => '010d106',
     'update-gitlab-shell-v-6-0-1'        => '2f61d70',
     'update-gitlab-shell-v-6-0-3'        => 'de78448',
-    '2-mb-file'                          => 'bf12d25'
+    '2-mb-file'                          => 'bf12d25',
+    'with-codeowners'                    => '219560e'
   }.freeze
 
   # gitlab-test-fork is a fork of gitlab-fork, but we don't necessarily