feat: serialize error payloads

.gitignore

@@ -56,3 +56,4 @@ Gemfile.lock
 # Used by RuboCop. Remote config files pulled in from inherit_from directive.
 .rubocop_cache
 # .rubocop-https?--*
+.idea

.release-please-manifest.json

@@ -1,3 +1,3 @@
 {
-  ".": "0.2.10"
+  ".": "0.2.11"
 }

.version.txt

@@ -1 +1 @@
-0.2.10
+0.2.11

Gemfile.lock

@@ -1,7 +1,7 @@
 PATH
   remote: .
   specs:
-    leopard (0.2.9)
+    leopard (0.2.11)
       concurrent-ruby (~> 1.1)
       dry-configurable (~> 1.3)
       dry-monads (~> 1.9)

lib/leopard/metrics_server.rb

@@ -2,6 +2,7 @@
 
 require 'socket'
 require 'erb'
+require 'json'
 
 module Rubyists
   module Leopard
@@ -62,8 +63,11 @@ def close_client(client)
       def write_metrics_response(client, request_line, workers)
         if request_line&.start_with?('GET /metrics')
           body = prometheus_metrics(workers)
+          content_type = body.is_a?(String) ? 'text/plain; version=0.0.4' : 'application/json'
+          body = JSON.generate(body) unless body.is_a?(String)
+
           client.write "HTTP/1.1 200 OK\r\n" \
-                       "Content-Type: text/plain; version=0.0.4\r\n" \
+                       "Content-Type: #{content_type}\r\n" \
                        "Content-Length: #{body.bytesize}\r\n\r\n#{body}"
         else
           client.write "HTTP/1.1 404 Not Found\r\nContent-Length: 0\r\n\r\n"

lib/leopard/version.rb

@@ -3,7 +3,7 @@
 module Rubyists
   module Leopard
     # x-release-please-start-version
-    VERSION = '0.2.10'
+    VERSION = '0.2.11'
     # x-release-please-end
   end
 end

test/lib/nats_api_server.rb

@@ -322,5 +322,22 @@ def instance_variable_get(name)
 
       assert_equal expected_metrics, @klass.send(:prometheus_metrics, workers)
     end
+
+    it 'serializes hash metrics payloads before writing the response' do
+      client = Object.new
+      response = nil
+      client.define_singleton_method(:write) { |payload| response = payload }
+
+      @klass.stub(:prometheus_metrics, { error: 'boom' }) do
+        @klass.send(:write_metrics_response, client, 'GET /metrics HTTP/1.1', [])
+      end
+
+      expected_body = '{"error":"boom"}'
+      expected_response = "HTTP/1.1 200 OK\r\n" \
+                          "Content-Type: application/json\r\n" \
+                          "Content-Length: #{expected_body.bytesize}\r\n\r\n#{expected_body}"
+
+      assert_equal expected_response, response
+    end
   end
 end