Fix export size doubling from re-exporting prior export blobs (#2707)

* Exclude export/import blobs and attachments from account exports

Export and import file blobs were being assigned the account's
account_id (via the Current.account default), causing subsequent
exports to include previous export/import ZIP files in the data.
This roughly doubled the export size each time and made imports
fail with an IntegrityError on unrecognized "Account::Export"
record type.

Filter out blobs attached to Export/Import records in
BlobRecordSet, FileRecordSet, and a new AttachmentRecordSet.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* Use STI base type for export blob exclusion filter

Rails polymorphic_name returns base_class.name for STI models,
so ActiveStorage stores record_type as "Export" rather than the
concrete subclass names. Filter on the base type accordingly.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* Fix export filtering for mixed-use Active Storage blobs

Exclude only internal-only blobs for account export metadata/file sets, scope attachment subqueries by account, and add regression coverage for blobs shared between user records and export attachments.

* Simplify export blob filtering

Exports always create fresh blobs, so a blob can never be legitimately
shared between an Export/Import and a real account record. Replace the
internal_only/external split with a single excluded_blob_ids subquery
and drop the contrived shared-blob test.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

app/models/account/data_transfer/active_storage/attachment_record_set.rb

@@ -0,0 +1,11 @@
+class Account::DataTransfer::ActiveStorage::AttachmentRecordSet < Account::DataTransfer::RecordSet
+  def initialize(account)
+    super(account: account, model: ::ActiveStorage::Attachment)
+  end
+
+  private
+    def records
+      ::ActiveStorage::Attachment.where(account: account)
+        .where.not(record_type: INTERNAL_RECORD_TYPES)
+    end
+end

app/models/account/data_transfer/active_storage/blob_record_set.rb

@@ -8,6 +8,14 @@ class Account::DataTransfer::ActiveStorage::BlobRecordSet < Account::DataTransfe
   end
 
   private
+    def records
+      ::ActiveStorage::Blob.where(account: account).where.not(id: excluded_blob_ids)
+    end
+
+    def excluded_blob_ids
+      ::ActiveStorage::Attachment.where(account: account, record_type: INTERNAL_RECORD_TYPES).select(:blob_id)
+    end
+
     def import_batch(files)
       batch_data = files.map do |file|
         data = load(file)

app/models/account/data_transfer/active_storage/file_record_set.rb

@@ -5,7 +5,11 @@ class Account::DataTransfer::ActiveStorage::FileRecordSet < Account::DataTransfe
 
   private
     def records
-      ::ActiveStorage::Blob.where(account: account)
+      ::ActiveStorage::Blob.where(account: account).where.not(id: excluded_blob_ids)
+    end
+
+    def excluded_blob_ids
+      ::ActiveStorage::Attachment.where(account: account, record_type: INTERNAL_RECORD_TYPES).select(:blob_id)
     end
 
     def export_record(blob)

app/models/account/data_transfer/manifest.rb

@@ -58,7 +58,7 @@ class Account::DataTransfer::Manifest
           ::Webhook::Delivery
         ),
         Account::DataTransfer::ActiveStorage::BlobRecordSet.new(account),
-        *build_record_sets(::ActiveStorage::Attachment),
+        Account::DataTransfer::ActiveStorage::AttachmentRecordSet.new(account),
         Account::DataTransfer::ActionText::RichTextRecordSet.new(account),
         Account::DataTransfer::ActiveStorage::FileRecordSet.new(account)
       ].then { set_importable_model_names(it) }

app/models/account/data_transfer/record_set.rb

@@ -3,6 +3,7 @@ class Account::DataTransfer::RecordSet
   class ConflictError < IntegrityError; end
 
   IMPORT_BATCH_SIZE = 100
+  INTERNAL_RECORD_TYPES = %w[Export Account::Import].freeze
 
   attr_accessor :importable_model_names
   attr_reader :account, :model, :attributes

test/models/account/export_test.rb

@@ -60,6 +60,37 @@ class Account::ExportTest < ActiveSupport::TestCase
     end
   end
 
+  test "export excludes blobs and attachments from previous exports" do
+    first_export = Account::Export.create!(account: Current.account, user: users(:david))
+    first_export.build
+    assert first_export.completed?
+
+    first_export_blob = first_export.file.blob
+    first_export_attachment = first_export.file.attachment
+
+    second_export = Account::Export.create!(account: Current.account, user: users(:david))
+    second_export.build
+    assert second_export.completed?
+
+    second_export.file.open do |file|
+      reader = ZipKit::FileReader.read_zip_structure(io: file)
+      filenames = reader.map(&:filename)
+
+      blob_entries = filenames.select { |f| f.start_with?("data/active_storage_blobs/") }
+      blob_ids = blob_entries.map { |f| File.basename(f, ".json") }
+      assert_not_includes blob_ids, first_export_blob.id, "Export should not include blob metadata from previous exports"
+
+      storage_entries = filenames.select { |f| f.start_with?("storage/") }
+      assert_not storage_entries.any? { |f| f == "storage/#{first_export_blob.key}" },
+        "Export should not include blob file from previous exports"
+
+      attachment_entries = filenames.select { |f| f.start_with?("data/active_storage_attachments/") }
+      attachment_ids = attachment_entries.map { |f| File.basename(f, ".json") }
+      assert_not_includes attachment_ids, first_export_attachment.id,
+        "Export should not include attachment records from previous exports"
+    end
+  end
+
   test "build succeeds when rich text references missing blob" do
     blob = ActiveStorage::Blob.create_and_upload!(
       io: file_fixture("moon.jpg").open,