FIX: Stop env mutation to allow all chained loggers to have the same …

…env (#110)

* FIX: Stop env mutation to allow all chained loggers to have the same env

* 2.3.4 doesn't like duping nil

lib/logster/base_store.rb

@@ -156,7 +156,7 @@ def report(severity, progname, msg, opts = {})
       msg = truncate_message(msg)
       message = Logster::Message.new(severity, progname, msg, opts[:timestamp], count: opts[:count])
 
-      env = opts[:env] || {}
+      env = opts[:env]&.dup || {}
       backtrace = opts[:backtrace]
       if Hash === env && env[:backtrace]
         # Special - passing backtrace through env

test/logster/test_base_store.rb

@@ -176,4 +176,16 @@ def test_log_message_is_truncated_when_above_maximum_message_length
   ensure
     Logster.config.maximum_message_length = orig
   end
+
+  def test_chained_loggers_shouldnt_mutate_env_passed_to_them
+    logger = Logster::Logger.new(@store)
+    other_store = Logster::TestStore.new
+    other_logger = Logster::Logger.new(other_store)
+    logger.chain(other_logger)
+    logger.add(Logger::WARN, "this is warning", '', { env: { backtrace: '11' } })
+    [@store, other_store].each do |store|
+      assert_equal('11', store.reported.first.backtrace)
+      refute_includes(store.reported.first.env.keys.map(&:to_sym), :backtrace)
+    end
+  end
 end