Improving readibility and further cleanup on CustomDiff

app/presenters/blob_presenter.rb

@@ -15,8 +15,8 @@ class BlobPresenter < Gitlab::View::Presenter::Delegated
 
     Gitlab::Highlight.highlight(
       blob.path,
-      Gitlab::Diff::CustomDiff.transformed_blob_data(blob) || limited_blob_data(to: to),
-      language: Gitlab::Diff::CustomDiff.transformed_blob_language(blob) || language,
+      blob_data,
+      language: blob_language,
       plain: plain
     )
   end
@@ -27,6 +27,14 @@ class BlobPresenter < Gitlab::View::Presenter::Delegated
     highlight(plain: false)
   end
 
+  def blob_data
+    @_blob_data ||= Gitlab::Diff::CustomDiff.transformed_blob_data(blob) || limited_blob_data(to: to)
+  end
+
+  def blob_language
+    @_blob_language ||= Gitlab::Diff::CustomDiff.transformed_blob_language(blob) || language
+  end
+
   def raw_plain_data
     blob.data unless blob.binary?
   end

lib/gitlab/diff/custom_diff.rb

@@ -6,22 +6,23 @@ module Gitlab
         def preprocess_before_diff(path, old_blob, new_blob)
           return unless path.ends_with? '.ipynb'
 
-          transformed_diff = IpynbDiff.diff(old_blob&.data, new_blob&.data,
-                                            diff_opts: { context: 5, include_diff_info: true },
-                                            transform_options: { cell_decorator: :percent },
-                                            raise_if_invalid_notebook: true)
-          new_diff = strip_diff_frontmatter(transformed_diff)
-
-          transformed_for_diff(new_blob, old_blob) if new_diff
-
-          Gitlab::AppLogger.info({ message: new_diff ? 'IPYNB_DIFF_GENERATED' : 'IPYNB_DIFF_NIL' })
-
-          new_diff
+          transformed_diff(old_blob&.data, new_blob&.data)&.tap do
+            transformed_for_diff(new_blob, old_blob)
+            Gitlab::AppLogger.info({ message: 'IPYNB_DIFF_GENERATED' })
+          end
         rescue IpynbDiff::InvalidNotebookError => e
           Gitlab::ErrorTracking.log_exception(e)
           nil
         end
 
+        def transformed_diff(before, after)
+          transformed_diff = IpynbDiff.diff(before, after,
+                                            diff_opts: { context: 5, include_diff_info: true },
+                                            transform_options: { cell_decorator: :percent },
+                                            raise_if_invalid_notebook: true)
+          strip_diff_frontmatter(transformed_diff)
+        end
+
         def transformed_blob_language(blob)
           'md' if transformed_for_diff?(blob)
         end

lib/gitlab/diff/file.rb

@@ -48,7 +48,7 @@ module Gitlab
       end
 
       def use_custom_diff?
-        Feature.enabled?(:jupyter_clean_diffs, repository.project, default_enabled: true)
+        strong_memoize(:_custom_diff_enabled)  { Feature.enabled?(:jupyter_clean_diffs, repository.project, default_enabled: true) }
       end
 
       def position(position_marker, position_type: :text)

lib/gitlab/git/blob.rb

@@ -24,7 +24,7 @@ module Gitlab
       LFS_POINTER_MIN_SIZE = 120.bytes
       LFS_POINTER_MAX_SIZE = 200.bytes
 
-      attr_accessor :size, :mode, :id, :commit_id, :loaded_size, :binary, :transformed_for_diff
+      attr_accessor :size, :mode, :id, :commit_id, :loaded_size, :binary
       attr_writer :name, :path, :data
 
       def self.gitlab_blob_truncated_true
@@ -127,7 +127,6 @@ module Gitlab
         # Retain the actual size before it is encoded
         @loaded_size = @data.bytesize if @data
         @loaded_all_data = @loaded_size == size
-        @transformed_for_diff = false
 
         record_metric_blob_size
         record_metric_truncated(truncated?)