Allow third-party previewers/analyzers to customize their tempdirs

2 files changed, 10 insertions, 3 deletions

diff --git a/activestorage/lib/active_storage/downloading.rb b/activestorage/lib/active_storage/downloading.rb
index ceb7cce0c7..3dac6b116a 100644
--- a/activestorage/lib/active_storage/downloading.rb
+++ b/activestorage/lib/active_storage/downloading.rb
@@ -3,9 +3,9 @@
 module ActiveStorage
   module Downloading
     private
-      # Opens a new tempfile and copies blob data into it. Yields the tempfile.
+      # Opens a new tempfile in #tempdir and copies blob data into it. Yields the tempfile.
       def download_blob_to_tempfile # :doc:
-        Tempfile.open("ActiveStorage") do |file|
+        Tempfile.open("ActiveStorage", tempdir) do |file|
           download_blob_to file
           yield file
         end
@@ -17,5 +17,10 @@ module ActiveStorage
         blob.download { |chunk| file.write(chunk) }
         file.rewind
       end
+
+      # Returns the directory in which tempfiles should be opened. Defaults to +Dir.tmpdir+.
+      def tempdir # :doc:
+        Dir.tmpdir
+      end
   end
 end
diff --git a/activestorage/lib/active_storage/previewer.rb b/activestorage/lib/active_storage/previewer.rb
index 460f6d5678..ed75bae3b5 100644
--- a/activestorage/lib/active_storage/previewer.rb
+++ b/activestorage/lib/active_storage/previewer.rb
@@ -40,8 +40,10 @@ module ActiveStorage
       #       end
       #     end
       #   end
+      #
+      # The output tempfile is opened in the directory returned by ActiveStorage::Downloading#tempdir.
       def draw(*argv) # :doc:
-        Tempfile.open("ActiveStorage") do |file|
+        Tempfile.open("ActiveStorage", tempdir) do |file|
           capture(*argv, to: file)
           yield file
         end