Moving CustomDiff to /lib folder

app/helpers/custom_diff_helper.rb

-# frozen_string_literal: true
-
-module CustomDiffHelper
-  class << self
-    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
-    rescue IpynbDiff::InvalidNotebookError => e
-      Gitlab::ErrorTracking.log_exception(e)
-      nil
-    end
-
-    def transformed_blob_language(blob)
-      'md' if transformed_for_diff?(blob)
-    end
-
-    def transformed_blob_data(blob)
-      if transformed_for_diff?(blob)
-        IpynbDiff.transform(blob.data,
-                            raise_errors: true,
-                            options: { include_metadata: false, cell_decorator: :percent })
-      end
-    end
-
-    def strip_diff_frontmatter(diff_content)
-      diff_content.scan(/.*\n/)[2..-1]&.join('') if diff_content.present?
-    end
-
-    def blobs_with_transformed_diffs
-      @blobs_with_transformed_diffs ||= {}
-    end
-
-    def transformed_for_diff?(blob)
-      blobs_with_transformed_diffs[blob]
-    end
-
-    def transformed_for_diff(*blobs)
-      blobs.each do |b|
-        blobs_with_transformed_diffs[b] = true if b
-      end
-    end
-  end
-end

app/presenters/blob_presenter.rb

@@ -15,8 +15,8 @@ class BlobPresenter < Gitlab::View::Presenter::Delegated
 
     Gitlab::Highlight.highlight(
       blob.path,
-      CustomDiffHelper.transformed_blob_data(blob) || limited_blob_data(to: to),
-      language: CustomDiffHelper.transformed_blob_language(blob) || language,
+      Gitlab::Diff::CustomDiff.transformed_blob_data(blob) || limited_blob_data(to: to),
+      language: Gitlab::Diff::CustomDiff.transformed_blob_language(blob) || language,
       plain: plain
     )
   end

lib/gitlab/diff/custom_diff.rb

+# frozen_string_literal: true
+module Gitlab
+  module Diff
+    module CustomDiff
+      class << self
+        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
+        rescue IpynbDiff::InvalidNotebookError => e
+          Gitlab::ErrorTracking.log_exception(e)
+          nil
+        end
+
+        def transformed_blob_language(blob)
+          'md' if transformed_for_diff?(blob)
+        end
+
+        def transformed_blob_data(blob)
+          if transformed_for_diff?(blob)
+            IpynbDiff.transform(blob.data,
+                                raise_errors: true,
+                                options: { include_metadata: false, cell_decorator: :percent })
+          end
+        end
+
+        def strip_diff_frontmatter(diff_content)
+          diff_content.scan(/.*\n/)[2..-1]&.join('') if diff_content.present?
+        end
+
+        def blobs_with_transformed_diffs
+          @blobs_with_transformed_diffs ||= {}
+        end
+
+        def transformed_for_diff?(blob)
+          blobs_with_transformed_diffs[blob]
+        end
+
+        def transformed_for_diff(*blobs)
+          blobs.each do |b|
+            blobs_with_transformed_diffs[b] = true if b
+          end
+        end
+      end
+    end
+  end
+end

lib/gitlab/diff/file.rb

@@ -44,7 +44,7 @@ module Gitlab
         new_blob_lazy
         old_blob_lazy
 
-        diff.diff = CustomDiffHelper.preprocess_before_diff(diff.new_path, old_blob_lazy, new_blob_lazy) || diff.diff if use_custom_diff?
+        diff.diff = Gitlab::Diff::CustomDiff.preprocess_before_diff(diff.new_path, old_blob_lazy, new_blob_lazy) || diff.diff if use_custom_diff?
       end
 
       def use_custom_diff?

spec/helpers/custom_diff_helper_spec.rb → spec/lib/gitlab/diff/custom_diff_spec.rb

@@ -2,7 +2,7 @@
 
 require 'spec_helper'
 
-RSpec.describe CustomDiffHelper do
+RSpec.describe Gitlab::Diff::CustomDiff do
   include RepoHelpers
 
   let(:project) { create(:project, :repository) }
@@ -10,53 +10,53 @@ RSpec.describe CustomDiffHelper do
   let(:ipynb_blob) { repository.blob_at('f6b7a707', 'files/ipython/markdown-table.ipynb') }
   let(:blob) { repository.blob_at('HEAD', 'files/ruby/regex.rb') }
 
-  describe "#preprocess_before_diff" do
+  describe '#preprocess_before_diff' do
     context 'for ipynb files' do
       it 'transforms the diff' do
-        expect(CustomDiffHelper.preprocess_before_diff(ipynb_blob.path, nil, ipynb_blob)).not_to include('cells')
+        expect(described_class.preprocess_before_diff(ipynb_blob.path, nil, ipynb_blob)).not_to include('cells')
       end
 
       it 'adds the blob to the list of transformed blobs' do
-        CustomDiffHelper.preprocess_before_diff(ipynb_blob.path, nil, ipynb_blob)
+        described_class.preprocess_before_diff(ipynb_blob.path, nil, ipynb_blob)
 
-        expect(CustomDiffHelper.transformed_for_diff?(ipynb_blob)).to be_truthy
+        expect(described_class.transformed_for_diff?(ipynb_blob)).to be_truthy
       end
     end
 
     context 'for other files' do
       it 'returns nil' do
-        expect(CustomDiffHelper.preprocess_before_diff(blob.path, nil, blob)).to be_nil
+        expect(described_class.preprocess_before_diff(blob.path, nil, blob)).to be_nil
       end
 
       it 'does not add the blob to the list of transformed blobs' do
-        CustomDiffHelper.preprocess_before_diff(blob.path, nil, blob)
+        described_class.preprocess_before_diff(blob.path, nil, blob)
 
-        expect(CustomDiffHelper.transformed_for_diff?(blob)).to be_falsey
+        expect(described_class.transformed_for_diff?(blob)).to be_falsey
       end
     end
   end
 
-  describe "#transformed_blob_data" do
+  describe '#transformed_blob_data' do
     it 'transforms blob data if file was processed' do
-      CustomDiffHelper.preprocess_before_diff(ipynb_blob.path, nil, ipynb_blob)
+      described_class.preprocess_before_diff(ipynb_blob.path, nil, ipynb_blob)
 
-      expect(CustomDiffHelper.transformed_blob_data(ipynb_blob)).not_to include('cells')
+      expect(described_class.transformed_blob_data(ipynb_blob)).not_to include('cells')
     end
 
-    it 'transforms blob data if file was not processed' do
-      expect(CustomDiffHelper.transformed_blob_data(ipynb_blob)).to be_nil
+    it 'does not transform blob data if file was not processed' do
+      expect(described_class.transformed_blob_data(ipynb_blob)).to be_nil
     end
   end
 
-  describe "#transformed_blob_language" do
-    it 'is when file was preprocessed' do
-      CustomDiffHelper.preprocess_before_diff(ipynb_blob.path, nil, ipynb_blob)
+  describe '#transformed_blob_language' do
+    it 'is md when file was preprocessed' do
+      described_class.preprocess_before_diff(ipynb_blob.path, nil, ipynb_blob)
 
-      expect(CustomDiffHelper.transformed_blob_language(ipynb_blob)).to eq('md')
+      expect(described_class.transformed_blob_language(ipynb_blob)).to eq('md')
     end
 
-    it 'is nil for .ipynb, but blob when it was not preprocessed' do
-      expect(CustomDiffHelper.transformed_blob_language(ipynb_blob)).to be_nil
+    it 'is nil for a .ipynb blob that was not preprocessed' do
+      expect(described_class.transformed_blob_language(ipynb_blob)).to be_nil
     end
   end
 end

spec/presenters/blob_presenter_spec.rb

@@ -161,7 +161,7 @@ RSpec.describe BlobPresenter do
       let(:git_blob) { blob.__getobj__ }
 
       before do
-        allow(CustomDiffHelper).to receive(:transformed_for_diff?).and_return(true)
+        allow(Gitlab::Diff::CustomDiff).to receive(:transformed_for_diff?).and_return(true)
       end
 
       it 'uses md as the transformed language' do