thumbnails and other derivatives were not stored in the path we expected them to be

app/services/hyrax/derivative_bucketed_storage.rb

@@ -0,0 +1,25 @@
+# frozen_string_literal: true
+
+# this class overrides the Valkyrie::Storage::Disk::BucketStorage class so that file paths match
+module Hyrax
+  class DerivativeBucketedStorage
+    attr_reader :base_path
+
+    def initialize(base_path:)
+      @base_path = base_path
+    end
+
+    # rubocop:disable Lint/UnusedMethodArgument
+    def generate(resource:, file:, original_filename:)
+      raise ArgumentError, "original_filename must be provided" unless original_filename
+      Pathname.new(base_path).join(*bucketed_path(resource.id)).join(original_filename)
+    end
+    # rubocop:enable Lint/UnusedMethodArgument
+
+    def bucketed_path(id)
+      # We want to use the same code the derivative process uses so that items end up
+      # stored in the place we expect them.
+      Hyrax::DerivativePath.new(id.to_s).pair_directory
+    end
+  end
+end

app/services/hyrax/derivative_path.rb

@@ -35,6 +35,18 @@ def all_paths
       end
     end
 
+    def pairs
+      @pairs ||= id.split('').each_slice(2).map(&:join)
+    end
+
+    def pair_directory
+      pairs[0..-2]
+    end
+
+    def pair_path
+      (pair_directory + pairs[-1..-1]).join('/')
+    end
+
     private
 
     # @return [String] Returns the root path where derivatives will be generated into.
@@ -47,10 +59,6 @@ def path_prefix
       Pathname.new(Hyrax.config.derivatives_path).join(pair_path)
     end
 
-    def pair_path
-      id.split('').each_slice(2).map(&:join).join('/')
-    end
-
     def file_name
       return unless destination_name
       destination_name + extension

app/services/hyrax/valkyrie_persist_derivatives.rb

@@ -25,11 +25,13 @@ def self.call(stream,
       # responds to #path -- here we only have a StringIO, so some
       # transformation is in order
       tmpfile = Tempfile.new(file_set.id, encoding: 'ascii-8bit')
-      tmpfile.write stream.read
+      stream.rewind
+      output = tmpfile.write(stream.read)
+      tmpfile.flush
+      raise 'blank file detected' if output.zero?
 
       filename = filename(directives)
       Hyrax.logger.debug "Uploading thumbnail for FileSet #{file_set.id} as #{filename}"
-
       uploader.upload(
         io: tmpfile,
         filename: filename,

config/initializers/storage_adapter_initializer.rb

@@ -7,6 +7,6 @@
 )
 
 Valkyrie::StorageAdapter.register(
-  Valkyrie::Storage::Disk.new(base_path: Hyrax.config.derivatives_path),
+  Valkyrie::Storage::Disk.new(base_path: Hyrax.config.derivatives_path, path_generator: Hyrax::DerivativeBucketedStorage),
   :derivatives_disk
 )