Ignore ActiveRecord::InvalidForeignKey in ActiveStorage::Blob#purge

Do nothing instead of raising an error when it’s called on an attached blob.

activestorage/app/jobs/active_storage/purge_job.rb

@@ -2,7 +2,7 @@
 
 # Provides asynchronous purging of ActiveStorage::Blob records via ActiveStorage::Blob#purge_later.
 class ActiveStorage::PurgeJob < ActiveStorage::BaseJob
-  discard_on ActiveRecord::RecordNotFound, ActiveRecord::InvalidForeignKey
+  discard_on ActiveRecord::RecordNotFound
 
   def perform(blob)
     blob.purge

activestorage/app/models/active_storage/blob.rb

@@ -207,6 +207,7 @@ class ActiveStorage::Blob < ActiveRecord::Base
   def purge
     destroy
     delete
+  rescue ActiveRecord::InvalidForeignKey
   end
 
   # Enqueues an ActiveStorage::PurgeJob to call #purge. This is the recommended way to purge blobs from a transaction,

activestorage/test/models/attached/many_test.rb

@@ -468,6 +468,33 @@ class ActiveStorage::ManyAttachedTest < ActiveSupport::TestCase
     end
   end
 
+  test "purging attachment with shared blobs" do
+    [
+      create_blob(filename: "funky.jpg"),
+      create_blob(filename: "town.jpg"),
+      create_blob(filename: "worm.jpg")
+    ].tap do |blobs|
+      @user.highlights.attach blobs
+      assert @user.highlights.attached?
+
+      another_user = User.create!(name: "John")
+      shared_blobs = [blobs.second, blobs.third]
+      another_user.highlights.attach shared_blobs
+      assert another_user.highlights.attached?
+
+      @user.highlights.purge
+      assert_not @user.highlights.attached?
+
+      assert_not ActiveStorage::Blob.exists?(blobs.first.id)
+      assert ActiveStorage::Blob.exists?(blobs.second.id)
+      assert ActiveStorage::Blob.exists?(blobs.third.id)
+
+      assert_not ActiveStorage::Blob.service.exist?(blobs.first.key)
+      assert ActiveStorage::Blob.service.exist?(blobs.second.key)
+      assert ActiveStorage::Blob.service.exist?(blobs.third.key)
+    end
+  end
+
   test "purging later" do
     [ create_blob(filename: "funky.jpg"), create_blob(filename: "town.jpg") ].tap do |blobs|
       @user.highlights.attach blobs
@@ -485,6 +512,35 @@ class ActiveStorage::ManyAttachedTest < ActiveSupport::TestCase
     end
   end
 
+  test "purging attachment later with shared blobs" do
+    [
+      create_blob(filename: "funky.jpg"),
+      create_blob(filename: "town.jpg"),
+      create_blob(filename: "worm.jpg")
+    ].tap do |blobs|
+      @user.highlights.attach blobs
+      assert @user.highlights.attached?
+
+      another_user = User.create!(name: "John")
+      shared_blobs = [blobs.second, blobs.third]
+      another_user.highlights.attach shared_blobs
+      assert another_user.highlights.attached?
+
+      perform_enqueued_jobs do
+        @user.highlights.purge_later
+      end
+
+      assert_not @user.highlights.attached?
+      assert_not ActiveStorage::Blob.exists?(blobs.first.id)
+      assert ActiveStorage::Blob.exists?(blobs.second.id)
+      assert ActiveStorage::Blob.exists?(blobs.third.id)
+
+      assert_not ActiveStorage::Blob.service.exist?(blobs.first.key)
+      assert ActiveStorage::Blob.service.exist?(blobs.second.key)
+      assert ActiveStorage::Blob.service.exist?(blobs.third.key)
+    end
+  end
+
   test "purging dependent attachment later on destroy" do
     [ create_blob(filename: "funky.jpg"), create_blob(filename: "town.jpg") ].tap do |blobs|
       @user.highlights.attach blobs

activestorage/test/models/attached/one_test.rb

@@ -412,6 +412,22 @@ class ActiveStorage::OneAttachedTest < ActiveSupport::TestCase
     end
   end
 
+  test "purging an attachment with a shared blob" do
+    create_blob(filename: "funky.jpg").tap do |blob|
+      @user.avatar.attach blob
+      assert @user.avatar.attached?
+
+      another_user = User.create!(name: "John")
+      another_user.avatar.attach blob
+      assert another_user.avatar.attached?
+
+      @user.avatar.purge
+      assert_not @user.avatar.attached?
+      assert ActiveStorage::Blob.exists?(blob.id)
+      assert ActiveStorage::Blob.service.exist?(blob.key)
+    end
+  end
+
   test "purging later" do
     create_blob(filename: "funky.jpg").tap do |blob|
       @user.avatar.attach blob
@@ -427,6 +443,25 @@ class ActiveStorage::OneAttachedTest < ActiveSupport::TestCase
     end
   end
 
+  test "purging an attachment later with shared blob" do
+    create_blob(filename: "funky.jpg").tap do |blob|
+      @user.avatar.attach blob
+      assert @user.avatar.attached?
+
+      another_user = User.create!(name: "John")
+      another_user.avatar.attach blob
+      assert another_user.avatar.attached?
+
+      perform_enqueued_jobs do
+        @user.avatar.purge_later
+      end
+
+      assert_not @user.avatar.attached?
+      assert ActiveStorage::Blob.exists?(blob.id)
+      assert ActiveStorage::Blob.service.exist?(blob.key)
+    end
+  end
+
   test "purging dependent attachment later on destroy" do
     create_blob(filename: "funky.jpg").tap do |blob|
       @user.avatar.attach blob

activestorage/test/models/blob_test.rb

@@ -174,10 +174,10 @@ class ActiveStorage::BlobTest < ActiveSupport::TestCase
     assert_not ActiveStorage::Blob.service.exist?(variant.key)
   end
 
-  test "purge fails when attachments exist" do
+  test "purge does nothing when attachments exist" do
     create_blob.tap do |blob|
       User.create! name: "DHH", avatar: blob
-      assert_raises(ActiveRecord::InvalidForeignKey) { blob.purge }
+      assert_no_difference(-> { ActiveStorage::Blob.count }) { blob.purge }
       assert ActiveStorage::Blob.service.exist?(blob.key)
     end
   end