Polish sync retry handling comments and assertions

Co-authored-by: jjmata <187772+jjmata@users.noreply.github.com>
Agent-Logs-Url: https://github.com/we-promise/sure/sessions/ea7a06f4-8344-4a00-877a-eda8cdfdc16a

app/models/sync.rb

@@ -105,6 +105,8 @@ class Sync < ApplicationRecord
   def fail_for_retry_exhaustion!(error_message)
     Sync.transaction do
       lock!
+      # Retry exhaustion can leave the sync in `pending` because we reset it
+      # after each rate-limit error to make the next ActiveJob retry retryable.
       start! if pending?
       fail! if may_fail?
       update!(error: error_message)
@@ -118,9 +120,9 @@ class Sync < ApplicationRecord
     Sync.transaction do
       lock!
 
+      return if pending?
       # If this is the "parent" and there are still children running, don't finalize.
       return unless all_children_finalized?
-      return if pending?
 
       if syncing?
         if has_failed_children?

test/models/sync_test.rb

@@ -59,6 +59,7 @@ class SyncTest < ActiveSupport::TestCase
     sync.reload
     assert_equal "pending", sync.status
     assert_nil sync.error
+    assert_not_nil sync.pending_at
     assert_nil sync.syncing_at
     assert_nil sync.failed_at
     assert_nil sync.completed_at