[Gem] Fixes User-Agent code for Elasticsearch client

In the migration to 8.x, the user agent code was extracted into
transport, since we're now using that library in other projects. So
for the Elasticsearch Client, the user-agent would be reported as the
one defined in elastic-transport. This code fixes the issue and brings
back the user agent in the format that was being used in 7.x

Author: picandocodigo

Diff for: elasticsearch/lib/elasticsearch.rb

@@ -46,14 +46,8 @@ def initialize(arguments = {}, &block)
       @warned = false
       @opaque_id_prefix = arguments[:opaque_id_prefix] || nil
       api_key(arguments) if arguments[:api_key]
-      if arguments[:cloud_id]
-        arguments[:hosts] = setup_cloud_host(
-          arguments[:cloud_id],
-          arguments[:user],
-          arguments[:password],
-          arguments[:port]
-        )
-      end
+      setup_cloud(arguments) if arguments[:cloud_id]
+      set_user_agent!(arguments) unless sent_user_agent?(arguments)
       @transport = Elastic::Transport::Client.new(arguments, &block)
     end
 
@@ -139,6 +133,15 @@ def api_key(arguments)
       end
     end
 
+    def setup_cloud(arguments)
+      arguments[:hosts] = setup_cloud_host(
+        arguments[:cloud_id],
+        arguments[:user],
+        arguments[:password],
+        arguments[:port]
+      )
+    end
+
     # Encode credentials for the Authorization Header
     # Credentials is the base64 encoding of id and api_key joined by a colon
     # @see https://www.elastic.co/guide/en/elasticsearch/reference/current/security-api-create-api-key.html
@@ -149,6 +152,25 @@ def encode(api_key)
     def elasticsearch_validation_request
       @transport.perform_request('GET', '/')
     end
+
+    def sent_user_agent?(arguments)
+      return unless (headers = arguments&.[](:transport_options)&.[](:headers))
+      !!headers.keys.detect { |h| h =~ /user-?_?agent/ }
+    end
+
+    def set_user_agent!(arguments)
+      user_agent = [
+        "elasticsearch-ruby/#{Elasticsearch::VERSION}",
+        "elastic-transport-ruby/#{Elastic::Transport::VERSION}",
+        "RUBY_VERSION: #{RUBY_VERSION}"
+      ]
+      if RbConfig::CONFIG && RbConfig::CONFIG['host_os']
+        user_agent << "#{RbConfig::CONFIG['host_os'].split('_').first[/[a-z]+/i].downcase} #{RbConfig::CONFIG['target_cpu']}"
+      end
+      arguments[:transport_options] ||= {}
+      arguments[:transport_options][:headers] ||= {}
+      arguments[:transport_options][:headers].merge!({ user_agent: user_agent.join('; ')})
+    end
   end
 
   # Error class for when we detect an unsupported version of Elasticsearch

Diff for: elasticsearch/spec/unit/user_agent_spec.rb

@@ -0,0 +1,69 @@
+# Licensed to Elasticsearch B.V. under one or more contributor
+# license agreements. See the NOTICE file distributed with
+# this work for additional information regarding copyright
+# ownership. Elasticsearch B.V. licenses this file to you under
+# the Apache License, Version 2.0 (the "License"); you may
+# not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+require 'spec_helper'
+
+describe Elasticsearch::Client do
+  let(:user_agent) {
+    "elasticsearch-ruby/#{Elasticsearch::VERSION}; elastic-transport-ruby/#{Elastic::Transport::VERSION}; RUBY_VERSION: #{RUBY_VERSION}; #{RbConfig::CONFIG['host_os'].split('_').first[/[a-z]+/i].downcase} #{RbConfig::CONFIG['target_cpu']}"
+  }
+
+  context 'when no user-agent is set on initialization' do
+    let(:client) { described_class.new }
+
+    it 'has the expected header' do
+      expect(client.transport.options[:transport_options][:headers][:user_agent]).to eq user_agent
+    end
+  end
+
+  context 'when a header is specified on initialization' do
+    let(:client) do
+      described_class.new(
+        transport_options: { headers: { 'X-Test-Header' => 'Test' } }
+      )
+    end
+
+    it 'has the expected header' do
+      expect(client.transport.options[:transport_options][:headers][:user_agent]).to eq user_agent
+      expect(client.transport.options[:transport_options][:headers]['X-Test-Header']).to eq 'Test'
+    end
+  end
+
+  context 'when other transport_options are specified on initialization' do
+    let(:client) do
+      described_class.new(
+        transport_options: { params:  { format: 'yaml' } }
+      )
+    end
+
+    it 'has the expected header' do
+      expect(client.transport.options[:transport_options][:headers][:user_agent]).to eq user_agent
+      expect(client.transport.options[:transport_options][:params][:format]).to eq 'yaml'
+    end
+  end
+
+  context 'when :user_agent is specified on initialization' do
+    let(:client) do
+      described_class.new(
+        transport_options: { headers: { user_agent: 'TestApp' } }
+      )
+    end
+
+    it 'has the expected header' do
+      expect(client.transport.options[:transport_options][:headers][:user_agent]).to eq 'TestApp'
+    end
+  end
+end