Fix: Invalid JSON on gc-stats (#1801)

* Fix: Invalid JSON on gc-stats

Credits of this patch should be for @jdsundberg, who reported the issue
but never sent a patch. Link to his bug report is below.

Closes #1687.

* Update tests so JSON response is correctly parsed

JSON without a whitespace between key and values wasn't being correctly
parsed (for example: `key: 'value'` was processed ok, but `key:'value'`
wasn't).

lib/puma/app/status.rb

@@ -1,3 +1,5 @@
+require 'json'
+
 module Puma
   module App
     class Status
@@ -60,8 +62,7 @@ module Puma
           return rack_response(200, OK_STATUS)
 
         when /\/gc-stats$/
-          json = "{" + GC.stat.map { |k, v| "\"#{k}\": #{v}" }.join(",") + "}"
-          return rack_response(200, json)
+          return rack_response(200, GC.stat.to_json)
 
         when /\/stats$/
           return rack_response(200, @cli.stats)

test/test_cli.rb

@@ -1,6 +1,7 @@
 require_relative "helper"
 
 require "puma/cli"
+require "json"
 
 class TestCLI < Minitest::Test
   def setup
@@ -195,12 +196,7 @@ class TestCLI < Minitest::Test
 
     lines = body.split("\r\n")
     json_line = lines.detect { |l| l[0] == "{" }
-    pairs = json_line.scan(/\"[^\"]+\": [^,]+/)
-    gc_stats = {}
-    pairs.each do |p|
-      p =~ /\"([^\"]+)\": ([^,]+)/ || raise("Can't parse #{p.inspect}!")
-      gc_stats[$1] = $2
-    end
+    gc_stats = JSON.parse(json_line)
     gc_count_after = gc_stats["count"].to_i
 
     # Hitting the /gc route should increment the count by 1