Include blob ID in tempfile name for debugging convenience

activestorage/app/models/active_storage/blob.rb

@@ -168,6 +168,16 @@ class ActiveStorage::Blob < ActiveRecord::Base
 
   # Downloads the blob to a tempfile on disk. Yields the tempfile.
   #
+  # The tempfile's name is prefixed with +ActiveStorage-+ and the blob's ID. Its extension matches that of the blob.
+  #
+  # By default, the tempfile is created in <tt>Dir.tmpdir</tt>. Pass +tempdir:+ to create it in a different directory:
+  #
+  #   blob.open(tempdir: "/path/to/tmp") do |file|
+  #     # ...
+  #   end
+  #
+  # The tempfile is automatically closed and unlinked after the given block is executed.
+  #
   # Raises ActiveStorage::IntegrityError if the downloaded data does not match the blob's checksum.
   def open(tempdir: nil, &block)
     ActiveStorage::Downloader.new(self, tempdir: tempdir).download_blob_to_tempfile(&block)

activestorage/lib/active_storage/downloader.rb

@@ -19,7 +19,7 @@ module ActiveStorage
       attr_reader :blob, :tempdir
 
       def open_tempfile
-        file = Tempfile.open([ "ActiveStorage", tempfile_extension_with_delimiter ], tempdir)
+        file = Tempfile.open([ "ActiveStorage-#{blob.id}-", blob.filename.extension_with_delimiter ], tempdir)
 
         begin
           yield file
@@ -40,9 +40,5 @@ module ActiveStorage
           raise ActiveStorage::IntegrityError
         end
       end
-
-      def tempfile_extension_with_delimiter
-        blob.filename.extension_with_delimiter
-      end
   end
 end

activestorage/test/models/blob_test.rb

@@ -85,11 +85,15 @@ class ActiveStorage::BlobTest < ActiveSupport::TestCase
   end
 
   test "open with integrity" do
-    create_file_blob(filename: "racecar.jpg").open do |file|
-      assert file.binmode?
-      assert_equal 0, file.pos
-      assert_match(/\.jpg\z/, file.path)
-      assert_equal file_fixture("racecar.jpg").binread, file.read, "Expected downloaded file to match fixture file"
+    create_file_blob(filename: "racecar.jpg").tap do |blob|
+      blob.open do |file|
+        assert file.binmode?
+        assert_equal 0, file.pos
+        byebug
+        assert File.basename(file.path).starts_with?("ActiveStorage-#{blob.id}-")
+        assert file.path.ends_with?(".jpg")
+        assert_equal file_fixture("racecar.jpg").binread, file.read, "Expected downloaded file to match fixture file"
+      end
     end
   end