Add support for disabling checksum validation (#2896)

gems/aws-sdk-s3/CHANGELOG.md

@@ -1,6 +1,8 @@
 Unreleased Changes
 ------------------
 
+* Issue - Add support for disabling checksum validation in `Object#download_file` (#2893).
+
 1.132.0 (2023-07-24)
 ------------------
 

gems/aws-sdk-s3/lib/aws-sdk-s3/customizations/object.rb

@@ -496,8 +496,9 @@ def upload_file(source, options = {})
       #   the object has a stored checksum, it will be used to validate the
       #   download and will raise an `Aws::Errors::ChecksumError` if
       #   checksum validation fails. You may provide a `on_checksum_validated`
-      #   callback if you need to verify that validation occured and which
-      #   algorithm was used.
+      #   callback if you need to verify that validation occurred and which
+      #   algorithm was used.  To disable checksum validation, set
+      #   `checksum_mode` to "DISABLED".
       #
       # @option options [Callable] on_checksum_validated Called each time a
       #   request's checksum is validated with the checksum algorithm and the

gems/aws-sdk-s3/lib/aws-sdk-s3/file_downloader.rb

@@ -31,7 +31,13 @@ def download(destination, options = {})
           key: options[:key],
         }
         @params[:version_id] = options[:version_id] if options[:version_id]
-        @params[:checksum_mode] = options[:checksum_mode] || 'ENABLED'
+
+        # checksum_mode only supports the value "ENABLED"
+        # falsey values (false/nil) or "DISABLED" should be considered
+        # disabled and the api parameter should be unset.
+        if (checksum_mode = options.fetch(:checksum_mode, 'ENABLED'))
+          @params[:checksum_mode] = checksum_mode unless checksum_mode.upcase == 'DISABLED'
+        end
         @on_checksum_validated = options[:on_checksum_validated]
 
         validate!

gems/aws-sdk-s3/spec/object/download_file_spec.rb

@@ -212,6 +212,28 @@ module S3
           expect(callback_data[:called]).to eq(4)
         end
 
+        it 'supports disabling checksum_mode' do
+          expect(client).to receive(:head_object).with({
+            bucket: 'bucket',
+            key: 'small',
+            part_number: 1
+          }).and_return(
+            client.stub_data(
+              :head_object,
+              content_length: one_meg,
+              parts_count: nil
+            )
+          )
+
+          expect(client).to receive(:get_object).with({
+            bucket: 'bucket',
+            key: 'small',
+            response_target: path
+          }).exactly(1).times
+
+          small_obj.download_file(path, checksum_mode: 'DISABLED')
+        end
+
         it 'raises an error if an invalid mode is specified' do
           expect { large_obj.download_file(path, mode: 'invalid_mode') }
             .to raise_error(