Move checksum calculation to Upload.hexdigest

app/models/upload.rb

@@ -27,6 +27,16 @@ class Upload < ActiveRecord::Base
     )
   end
 
+  def self.hexdigest(absolute_path)
+    return unless exist?(absolute_path)
+
+    Digest::SHA256.file(absolute_path).hexdigest
+  end
+
+  def self.exist?(absolute_path)
+    File.exist?(absolute_path)
+  end
+
   def absolute_path
     return path unless relative_path?
 
@@ -36,11 +46,11 @@ class Upload < ActiveRecord::Base
   def calculate_checksum
     return unless exist?
 
-    self.checksum = Digest::SHA256.file(absolute_path).hexdigest
+    self.checksum = self.class.hexdigest(absolute_path)
   end
 
   def exist?
-    File.exist?(absolute_path)
+    self.class.exist?(absolute_path)
   end
 
   private

lib/gitlab/geo/file_uploader.rb

@@ -30,11 +30,7 @@ module Gitlab
       end
 
       def matches_checksum?(recorded_file)
-        message[:checksum] == calculate_checksum(recorded_file.absolute_path)
-      end
-
-      def calculate_checksum(absolute_path)
-        Digest::SHA256.file(absolute_path).hexdigest
+        message[:checksum] == Upload.hexdigest(recorded_file.absolute_path)
       end
 
       def success(file)

spec/models/upload_spec.rb

@@ -90,6 +90,28 @@ describe Upload, type: :model do
     end
   end
 
+  describe '.hexdigest' do
+    it 'calculates the SHA256 sum' do
+      expected = Digest::SHA256.file(__FILE__).hexdigest
+
+      expect(described_class.hexdigest(__FILE__)).to eq expected
+    end
+
+    it 'returns nil for a non-existant file' do
+      expect(described_class.hexdigest("#{__FILE__}-nope")).to be_nil
+    end
+  end
+
+  describe '.exist?' do
+    it 'returns true when the file exists' do
+      expect(described_class.exist?(__FILE__)).to eq true
+    end
+
+    it 'returns false when the file does not exist' do
+      expect(described_class.exist?("#{__FILE__}-nope")).to eq false
+    end
+  end
+
   describe '#absolute_path' do
     it 'returns the path directly when already absolute' do
       path = '/path/to/namespace/project/secret/file.jpg'