Fixes instantiating Client in Manticore implementation.

Backport from elastic-transport
elastic/elastic-transport-ruby#69

Author: picandocodigo

elasticsearch-transport/lib/elasticsearch/transport/transport/http/manticore.rb

@@ -87,14 +87,13 @@ def build_client(options = {})
           # @return [Response]
           # @see    Transport::Base#perform_request
           #
-          def perform_request(method, path, params={}, body=nil, headers=nil, opts={})
+          def perform_request(method, path, params = {}, body = nil, headers = nil, opts = {})
             super do |connection, url|
               body = body ? __convert_to_json(body) : nil
-              body, headers = compress_request(body, @request_options[:headers])
-
+              body, headers = compress_request(body, parse_headers(headers))
               params[:body] = body if body
               params[:headers] = headers if headers
-              params = params.merge(@request_options)
+
               case method
               when 'GET'
                 resp = connection.connection.get(url, params)
@@ -161,8 +160,14 @@ def host_unreachable_exceptions
 
           private
 
+          def parse_headers(headers)
+            request_headers = @request_options.fetch(:headers, {})
+            headers = request_headers.merge(headers || {})
+            headers.empty? ? nil : headers
+          end
+
           def apply_headers(options)
-            headers = options[:headers] || options.dig(:transport_options, :headers) || {}
+            headers = options[:headers].clone || options.dig(:transport_options, :headers).clone || {}
             headers[CONTENT_TYPE_STR] = find_value(headers, CONTENT_TYPE_REGEX) || DEFAULT_CONTENT_TYPE
             headers[USER_AGENT_STR] = find_value(headers, USER_AGENT_REGEX) || find_value(@request_options[:headers], USER_AGENT_REGEX) || user_agent_header
             headers[ACCEPT_ENCODING] = GZIP if use_compression?

elasticsearch-transport/spec/elasticsearch/transport/http/manticore_spec.rb

@@ -53,7 +53,7 @@
         expect(perform_request).to be_kind_of(Elasticsearch::Transport::Transport::Response)
       end
 
-      it 'run body with preper params' do
+      it 'run body with proper params' do
         expect(
           client.transport.connections.first.connection
         ).to receive(:post).with('http://localhost:9200/', { body: body, headers: expected_headers }).and_return(response)
@@ -138,6 +138,24 @@
           end
         end
       end
+
+      context 'headers' do
+        it 'sends custom headers' do
+          client = Elasticsearch::Transport::Client.new(
+            transport_class: described_class,
+            transport_options: { headers: { 'Elastic-Api-Version'=>'2023-10-31' } }
+          )
+          expect(
+            client.transport.connections.first.connection
+          ).to receive(:get).with(
+                 'http://localhost:9200/',
+                 {
+                   headers: expected_headers.merge({ 'Elastic-Api-Version'=>'2023-10-31' })
+                 }
+               ).and_return(response)
+          client.perform_request('GET', '/', {}, nil, headers)
+        end
+      end
     end
   end
 end

elasticsearch-transport/test/unit/transport_manticore_test.rb

@@ -111,7 +111,7 @@ def common_headers
                     {
                       body: '{"foo":"bar"}',
                       headers: {
-                        'Content-Type' => 'application/json',
+                        'Content-Type' => 'application/x-ndjson',
                         'User-Agent' => @transport.send(:user_agent_header)
                       }
                     }