Allow requesting files by their original filename

Allows links between files, like texture loading from glTF

app/controllers/model_files_controller.rb

@@ -159,7 +159,11 @@ class ModelFilesController < ApplicationController
       @file = @model.model_files.find_signed!(params[:id], purpose: "download")
       skip_authorization
     else
-      @file = @model.model_files.find_param(params[:id])
+      begin
+        @file = @model.model_files.find_param(params[:id])
+      rescue ActiveRecord::RecordNotFound
+        @file = @model.model_files.find_by!(filename: [params[:filename], params[:format]].join("."))
+      end
       authorize @file
     end
     @title = @file.name

config/routes.rb

@@ -146,4 +146,7 @@ Rails.application.routes.draw do
     skip_controllers :applications
   end
   resources :doorkeeper_applications, path: "/oauth/applications"
+
+  # Fallback route for filename matching
+  get "/models/:model_id/model_files/*filename" => "model_files#show", :as => "model_model_files_by_filename"
 end

spec/requests/model_files_spec.rb

@@ -177,5 +177,22 @@ RSpec.describe "Model Files" do
         expect(response).to redirect_to(model_path(model))
       end
     end
+
+    describe "GET /models/:model_id/model_files/:filename", :as_member do
+      describe "GET a model file from its filename" do
+        before do
+          create(:model_file, model: model, filename: "subfolder/test.stl")
+          get model_model_files_by_filename_path(model_id: model.to_param, filename: "subfolder/test", format: :stl)
+        end
+
+        it "returns http success" do
+          expect(response).to have_http_status(:success)
+        end
+
+        it "has correct MIME type" do
+          expect(response.media_type).to eq("model/stl")
+        end
+      end
+    end
   end
 end