Add an option to writer to avoid generating the ro-crate-preview

lib/ro_crate/writer.rb

@@ -14,9 +14,11 @@ def initialize(crate)
     #
     # @param dir [String] A path for the directory for the crate to be written to. All parent directories will be created.
     # @param overwrite [Boolean] Whether or not to overwrite existing files.
-    def write(dir, overwrite: true)
+    # @param skip_preview [Boolean] Whether or not to skip generation of the RO-Crate preview HTML file.
+    def write(dir, overwrite: true, skip_preview: false)
       FileUtils.mkdir_p(dir) # Make any parent directories
       @crate.payload.each do |path, entry|
+        next if skip_preview && entry&.source.is_a?(ROCrate::PreviewGenerator)
         fullpath = ::File.join(dir, path)
         next if !overwrite && ::File.exist?(fullpath)
         next if entry.directory?
@@ -40,10 +42,12 @@ def write(dir, overwrite: true)
     # Write the crate to a zip file.
     #
     # @param destination [String, ::File] The destination where to write the RO-Crate zip.
-    def write_zip(destination)
+    # @param skip_preview [Boolean] Whether or not to skip generation of the RO-Crate preview HTML file.
+    def write_zip(destination, skip_preview: false)
       Zip::File.open(destination, Zip::File::CREATE) do |zip|
         @crate.payload.each do |path, entry|
           next if entry.directory?
+          next if skip_preview && entry&.source.is_a?(ROCrate::PreviewGenerator)
           if entry.symlink?
             zip.add(path, entry.path) if entry.path
           else

test/writer_test.rb

@@ -274,4 +274,39 @@ class WriterTest < Test::Unit::TestCase
       end
     end
   end
+
+  test 'skip generating the preview in a directory' do
+    crate = ROCrate::Crate.new
+    crate.add_file(fixture_file('info.txt'))
+    crate.add_file(StringIO.new('just a string!'), 'notice.txt')
+    crate.add_file(fixture_file('data.csv'), 'directory/data.csv')
+
+    Dir.mktmpdir do |dir|
+      ROCrate::Writer.new(crate).write(dir, skip_preview: true)
+      assert ::File.exist?(::File.join(dir, ROCrate::Metadata::IDENTIFIER))
+      refute ::File.exist?(::File.join(dir, ROCrate::Preview::IDENTIFIER))
+      assert_equal 6, ::File.size(::File.join(dir, 'info.txt'))
+      assert_equal 14, ::File.size(::File.join(dir, 'notice.txt'))
+      assert_equal 20, ::File.size(::File.join(dir, 'directory', 'data.csv'))
+    end
+  end
+
+  test 'skip generating the preview in a zip file' do
+    crate = ROCrate::Crate.new
+    crate.add_directory(fixture_file('directory').path.to_s, 'fish')
+
+    Tempfile.create do |file|
+      ROCrate::Writer.new(crate).write_zip(file, skip_preview: true)
+
+      Zip::File.open(file) do |zipfile|
+        assert zipfile.file.exist?(ROCrate::Metadata::IDENTIFIER)
+        refute zipfile.file.exist?(ROCrate::Preview::IDENTIFIER)
+        assert zipfile.file.exist? 'fish/info.txt'
+        assert zipfile.file.exist? 'fish/root.txt'
+        assert zipfile.file.exist? 'fish/data/info.txt'
+        assert zipfile.file.exist? 'fish/data/nested.txt'
+        assert zipfile.file.exist? 'fish/data/binary.jpg'
+      end
+    end
+  end
 end