Handle application script errors consistently.

lib/utopia/exceptions/application_errors.rb

@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+# Released under the MIT License.
+# Copyright, 2026, by Samuel Williams.
+
+module Utopia
+	module Exceptions
+		# Exceptions raised by application code which can be safely handled and reported.
+		APPLICATION_ERRORS = [StandardError, ScriptError].freeze
+	end
+end

lib/utopia/exceptions/handler.rb

@@ -1,14 +1,15 @@
 # frozen_string_literal: true
 
 # Released under the MIT License.
-# Copyright, 2014-2025, by Samuel Williams.
+# Copyright, 2014-2026, by Samuel Williams.
 # Copyright, 2025, by Olle Jonsson.
 
 require "console"
 
 require_relative "../middleware"
 require_relative "../request"
 require_relative "../response"
+require_relative "application_errors"
 
 module Utopia
 	module Exceptions
@@ -37,7 +38,7 @@ def freeze
 			def call(request)
 				begin
 					return @delegate.call(request)
-				rescue Exception => exception
+				rescue *APPLICATION_ERRORS => exception
 					Console.warn(self, "An error occurred while processing the request.", error: exception)
 
 					begin
@@ -52,7 +53,7 @@ def call(request)
 						error_response.status = 500
 
 						return error_response
-					rescue Exception => exception
+					rescue *APPLICATION_ERRORS => exception
 						# If redirection fails, we also finish with a fatal error:
 						Console.error(self, "An error occurred while invoking the error handler.", error: exception)
 						return Response[500, {"content-type" => "text/plain"}, ["An error occurred while processing the request."]]

lib/utopia/exceptions/mailer.rb

@@ -1,14 +1,14 @@
 # frozen_string_literal: true
 
 # Released under the MIT License.
-# Copyright, 2016-2025, by Samuel Williams.
+# Copyright, 2016-2026, by Samuel Williams.
 
 require "net/smtp"
 require "mail"
 
 require_relative "../middleware"
 require_relative "../request"
-require_relative "handler"
+require_relative "application_errors"
 
 module Utopia
 	module Exceptions
@@ -59,7 +59,7 @@ def freeze
 			def call(request)
 				begin
 					return @delegate.call(request)
-				rescue => exception
+				rescue *APPLICATION_ERRORS => exception
 					request.exception = exception
 					send_notification exception, request
 

test/utopia/exceptions/.handler/controller.rb

@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 # Released under the MIT License.
-# Copyright, 2015-2023, by Samuel Williams.
+# Copyright, 2015-2026, by Samuel Williams.
 
 prepend Actions
 
@@ -12,6 +12,14 @@ class TharSheBlows < StandardError
 	raise TharSheBlows.new("Arrrh!")
 end
 
+on "syntax-error" do
+	raise SyntaxError.new("Invalid application syntax!")
+end
+
+on "interrupt" do
+	raise Interrupt.new("Application interrupted!")
+end
+
 # The ExceptionHandler middleware will redirect here when an exception occurs. If this also fails, things get ugly.
 on "exception" do |request|
 	if request.query_parameters["fatal"]

test/utopia/exceptions/handler.rb

@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 # Released under the MIT License.
-# Copyright, 2015-2025, by Samuel Williams.
+# Copyright, 2015-2026, by Samuel Williams.
 
 require "sus/fixtures/protocol/http/middleware_context"
 require "utopia/application"
@@ -35,4 +35,15 @@
 		expect(last_response.status).to be == 500
 		expect(last_response.read).to be(:include?, "Error: Arrrh!")
 	end
+
+	it "handles application syntax errors" do
+		client.get "/syntax-error"
+
+		expect(last_response.status).to be == 500
+		expect(last_response.read).to be(:include?, "Invalid application syntax!")
+	end
+
+	it "does not handle process exceptions" do
+		expect{client.get "/interrupt"}.to raise_exception(Interrupt, message: be =~ /Application interrupted/)
+	end
 end

test/utopia/exceptions/mailer.rb

@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 # Released under the MIT License.
-# Copyright, 2016-2025, by Samuel Williams.
+# Copyright, 2016-2026, by Samuel Williams.
 
 require "sus/fixtures/protocol/http/middleware_context"
 require "utopia/application"
@@ -43,6 +43,19 @@ def before
 		expect(last_mail.to_s).to be(:include?, "TharSheBlows")
 	end
 
+	it "reports application syntax errors" do
+		expect{client.get "/syntax-error"}.to raise_exception(SyntaxError, message: be =~ /Invalid application syntax/)
+
+		last_mail = Mail::TestMailer.deliveries.last
+		expect(last_mail.to_s).to be(:include?, "SyntaxError")
+	end
+
+	it "does not report process exceptions" do
+		expect{client.get "/interrupt"}.to raise_exception(Interrupt, message: be =~ /Application interrupted/)
+
+		expect(Mail::TestMailer.deliveries).to be(:empty?)
+	end
+
 	it "extracts rewindable request bodies" do
 		request = Utopia::Request["POST", "/", {}, ["Hello", " World!"]]
 		request.body.read