From 3291fa3630c456450f8c6a9b771f77c293d036cd Mon Sep 17 00:00:00 2001
From: Aidan Haran <aidanharan@Aidans-MacBook-Pro.local>
Date: Sat, 16 Sep 2017 19:59:32 +0100
Subject: Allow for custom handling of exceptions that are discarded

---
 activejob/CHANGELOG.md                  | 16 ++++++++++++++++
 activejob/lib/active_job/exceptions.rb  | 12 +++++++++++-
 activejob/test/cases/exceptions_test.rb |  7 +++++++
 activejob/test/jobs/retry_job.rb        |  2 ++
 4 files changed, 36 insertions(+), 1 deletion(-)

(limited to 'activejob')

diff --git a/activejob/CHANGELOG.md b/activejob/CHANGELOG.md
index 77dfdefc05..32bf5a4b50 100644
--- a/activejob/CHANGELOG.md
+++ b/activejob/CHANGELOG.md
@@ -1,3 +1,19 @@
+*   Allow block to be passed to ActiveJob::Base.discard_on to allow custom handling of discard jobs.
+
+    Example:
+
+        class RemoteServiceJob < ActiveJob::Base
+      	   discard_on(CustomAppException) do |job, exception|
+      	     ExceptionNotifier.caught(exception)
+           end
+
+          def perform(*args)
+            # Might raise CustomAppException for something domain specific
+          end
+        end
+
+    *Aidan Haran*
+    
 *   Change logging instrumentation to log errors when a job raises an exception.
 
     Fixes #26848.
diff --git a/activejob/lib/active_job/exceptions.rb b/activejob/lib/active_job/exceptions.rb
index dfc74deb1a..21d823eef9 100644
--- a/activejob/lib/active_job/exceptions.rb
+++ b/activejob/lib/active_job/exceptions.rb
@@ -61,18 +61,28 @@ module ActiveJob
       # Discard the job with no attempts to retry, if the exception is raised. This is useful when the subject of the job,
       # like an Active Record, is no longer available, and the job is thus no longer relevant.
       #
+      # You can also pass a block that'll be invoked. This block is yielded with the job instance as the first and the error instance as the second parameter.
+      #
       # ==== Example
       #
       #  class SearchIndexingJob < ActiveJob::Base
       #    discard_on ActiveJob::DeserializationError
+      #    discard_on(CustomAppException) do |job, exception|
+      #      ExceptionNotifier.caught(exception)
+      #    end
       #
       #    def perform(record)
       #      # Will raise ActiveJob::DeserializationError if the record can't be deserialized
+      #      # Might raise CustomAppException for something domain specific
       #    end
       #  end
       def discard_on(exception)
         rescue_from exception do |error|
-          logger.error "Discarded #{self.class} due to a #{exception}. The original exception was #{error.cause.inspect}."
+          if block_given?
+            yield self, exception
+          else
+            logger.error "Discarded #{self.class} due to a #{exception}. The original exception was #{error.cause.inspect}."
+          end
         end
       end
     end
diff --git a/activejob/test/cases/exceptions_test.rb b/activejob/test/cases/exceptions_test.rb
index 7a3c372143..7b8f1dcca7 100644
--- a/activejob/test/cases/exceptions_test.rb
+++ b/activejob/test/cases/exceptions_test.rb
@@ -58,6 +58,13 @@ class ExceptionsTest < ActiveJob::TestCase
     end
   end
 
+  test "custom handling of discarded job" do
+    perform_enqueued_jobs do
+      RetryJob.perform_later "CustomDiscardableError", 2
+      assert_equal "Dealt with a job that was discarded in a custom way", JobBuffer.last_value
+    end
+  end
+
   test "custom handling of job that exceeds retry attempts" do
     perform_enqueued_jobs do
       RetryJob.perform_later "CustomCatchError", 6
diff --git a/activejob/test/jobs/retry_job.rb b/activejob/test/jobs/retry_job.rb
index a12d09779b..2b22186f0a 100644
--- a/activejob/test/jobs/retry_job.rb
+++ b/activejob/test/jobs/retry_job.rb
@@ -10,6 +10,7 @@ class ExponentialWaitTenAttemptsError < StandardError; end
 class CustomWaitTenAttemptsError < StandardError; end
 class CustomCatchError < StandardError; end
 class DiscardableError < StandardError; end
+class CustomDiscardableError < StandardError; end
 
 class RetryJob < ActiveJob::Base
   retry_on DefaultsError
@@ -19,6 +20,7 @@ class RetryJob < ActiveJob::Base
   retry_on CustomWaitTenAttemptsError, wait: ->(executions) { executions * 2 }, attempts: 10
   retry_on(CustomCatchError) { |job, exception| JobBuffer.add("Dealt with a job that failed to retry in a custom way after #{job.arguments.second} attempts") }
   discard_on DiscardableError
+  discard_on(CustomDiscardableError) { |job, exception| JobBuffer.add("Dealt with a job that was discarded in a custom way") }
 
   def perform(raising, attempts)
     if executions < attempts
-- 
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