Rescue StandardErrors raised from exception's message (#4089)

* Rescue standard errors raised from exception's message

* Set a default message value if it raises an error

* Update default message value

* Add comments for exception_message

lib/sidekiq/job_retry.rb

@@ -140,9 +140,7 @@ module Sidekiq
         queue
       end
 
-      # App code can stuff all sorts of crazy binary data into the error message
-      # that won't convert to JSON.
-      m = exception.message.to_s[0, 10_000]
+      m = exception_message(exception).dup
       if m.respond_to?(:scrub!)
         m.force_encoding("utf-8")
         m.scrub!
@@ -247,5 +245,17 @@ module Sidekiq
         exception_caused_by_shutdown?(e.cause, checked_causes)
     end
 
+    # Extract message from exception.
+    # Set a default if the message raises an error
+    def exception_message(exception)
+      begin
+        # App code can stuff all sorts of crazy binary data into the error message
+        # that won't convert to JSON.
+        exception.message.to_s[0, 10_000]
+      rescue StandardError => e
+        "!!! ERROR MESSAGE THREW AN ERROR !!!"
+      end
+    end
+
   end
 end

test/test_retry.rb

@@ -10,6 +10,12 @@ class TestRetry < Minitest::Test
       include Sidekiq::Worker
     end
 
+    class BadErrorMessage < StandardError
+      def message
+        raise "Ahhh, this isn't supposed to happen"
+      end
+    end
+
     before do
       Sidekiq.redis {|c| c.flushdb }
     end
@@ -75,6 +81,19 @@ class TestRetry < Minitest::Test
       assert_equal "kerblammo! <20>", job["error_message"]
     end
 
+    # In the rare event that an error message raises an error itself,
+    # allow the job to retry. This will likely only happen for custom
+    # error classes that override #message
+    it 'handles error message that raises an error' do
+      assert_raises RuntimeError do
+        handler.local(worker, job, 'default') do
+          raise BadErrorMessage.new
+        end
+      end
+
+      assert_equal 1, Sidekiq::RetrySet.new.size
+      refute_nil job["error_message"]
+    end
 
     it 'allows a max_retries option in initializer' do
       max_retries = 7