Add output_server_strict config (#163)

Set `output_server_strict` to true to raise a 404 for missing files when running `bin/dev` after `perron:build`. This change prevents fallback to Rails server/render, avoiding confusion with incorrectly rendered pages.

Consider making this the default setting.

Author: eelcoj

lib/perron/configuration.rb

@@ -15,6 +15,8 @@ def initialize
 
       @config.output = "output"
 
+      @config.output_server_strict = false
+
       @config.mode = :standalone
 
       @config.live_reload = false

lib/perron/output_server.rb

@@ -8,6 +8,7 @@ def initialize(app)
 
     def call(environment)
       return @app.call(environment) if disabled?
+      return not_found if !static_file(environment) && Perron.configuration.output_server_strict
 
       static_file(environment).then do |file|
         file ? serve(file) : @app.call(environment)
@@ -41,6 +42,14 @@ def serve(file_path)
       ]
     end
 
+    def not_found
+      [
+        404,
+        {"Content-Type" => "text/plain"},
+        ["Not Found"]
+      ]
+    end
+
     def enabled? = Dir.exist?(output_path)
 
     def inject_preview_indicator(content)