Return a 404 error when attempting to access a deleted Whitehall asset

Currently, accessing a soft deleted asset returns a 404.  However, accessing a soft deleted Whitehall asset still attempts to proxy to S3, then returns the resulting XML and 404 proxied back from S3.  This commit changes that behaviour so that Whitehall assets are not proxied and a 404 is served from Asset Manager.

Note: the asset media controller uses `find` to get the records, which raises an exception if no records are found.  Whitehall media controller uses `find_by` which does not raise an exception, therefore we have to raise our own exception and rescue as a 404 in the event of no records being returned.

app/controllers/whitehall_media_controller.rb

@@ -2,10 +2,15 @@ class WhitehallMediaController < MediaController
 
 protected
 
+  class WhitehallAssetNotFound < StandardError
+  end
+
+  rescue_from WhitehallAssetNotFound, with: :error_404
+
   def asset
-    @asset ||= WhitehallAsset.from_params(
+    @asset ||= WhitehallAsset.undeleted.from_params(
       path: params[:path], format: params[:format], path_prefix: 'government/uploads/'
-    )
+    ) || raise(WhitehallAssetNotFound)
   end
 
   def asset_servable?

spec/controllers/whitehall_media_controller_spec.rb

@@ -253,5 +253,20 @@
         expect(response).to have_http_status(:not_found)
       end
     end
+
+    context 'with a soft deleted file' do
+      let(:state) { 'uploaded' }
+
+      before do
+        allow(WhitehallAsset).to receive(:find_by).with(legacy_url_path: legacy_url_path).and_return(nil)
+        asset.update_attribute(:deleted_at, Time.now)
+      end
+
+      it 'responds with not found status' do
+        get :download, params: { path: path, format: format }
+
+        expect(response).to have_http_status(:not_found)
+      end
+    end
   end
 end

spec/models/whitehall_asset_spec.rb

@@ -176,4 +176,31 @@
       end
     end
   end
+
+  describe 'soft deletion' do
+    let(:asset) { FactoryBot.create(:whitehall_asset) }
+
+    before do
+      asset.destroy
+    end
+
+    it 'adds a deleted_at timestamp to the record' do
+      expect(asset.deleted_at).not_to be_nil
+    end
+
+    it 'is not inclued in the "undeleted" scope' do
+      expect(Asset.undeleted).not_to include(asset)
+    end
+
+    it 'is included in the "deleted" scope' do
+      expect(Asset.deleted).to include(asset)
+    end
+
+    it 'can be restored' do
+      asset.destroy
+      expect(asset.deleted_at).not_to be_nil
+      asset.restore
+      expect(asset.deleted_at).to be_nil
+    end
+  end
 end