Fix customizing Content-Type via GCS service URLs

1 files changed, 7 insertions, 1 deletions

diff --git a/activestorage/lib/active_storage/service/gcs_service.rb b/activestorage/lib/active_storage/service/gcs_service.rb
index c13ce4786d..6f6f4105fe 100644
--- a/activestorage/lib/active_storage/service/gcs_service.rb
+++ b/activestorage/lib/active_storage/service/gcs_service.rb
@@ -16,7 +16,13 @@ module ActiveStorage
     def upload(key, io, checksum: nil)
       instrument :upload, key: key, checksum: checksum do
         begin
-          bucket.create_file(io, key, md5: checksum)
+          # The official GCS client library doesn't allow us to create a file with no Content-Type metadata.
+          # We need the file we create to have no Content-Type so we can control it via the response-content-type
+          # param in signed URLs. Workaround: let the GCS client create the file with an inferred
+          # Content-Type (usually "application/octet-stream") then clear it.
+          bucket.create_file(io, key, md5: checksum).update do |file|
+            file.content_type = nil
+          end
         rescue Google::Cloud::InvalidArgumentError
           raise ActiveStorage::IntegrityError
         end