ActionDispatch::Executor: report errors handled by ShowExceptions

Fix: https://github.com/rails/rails/issues/51002

In the default middleware stack, the `ShowExceptions` middleware is
lower than `ActionDispatch::Execturor` and will handle most exceptions
causing `Executor` not to witness any.

Instead we need to rely on `action_dispatch.exception` being added
into the request env.

actionpack/lib/action_dispatch/middleware/executor.rb

@@ -14,6 +14,9 @@ module ActionDispatch
       state = @executor.run!(reset: true)
       begin
         response = @app.call(env)
+        if rendered_error = env["action_dispatch.exception"]
+          @executor.error_reporter.report(rendered_error, handled: false, source: "application.action_dispatch")
+        end
         returned = response << ::Rack::BodyProxy.new(response.pop) { state.complete! }
       rescue => error
         @executor.error_reporter.report(error, handled: false, source: "application.action_dispatch")

actionpack/lib/action_dispatch/middleware/show_exceptions.rb

@@ -34,8 +34,10 @@ module ActionDispatch
       request = ActionDispatch::Request.new env
       backtrace_cleaner = request.get_header("action_dispatch.backtrace_cleaner")
       wrapper = ExceptionWrapper.new(backtrace_cleaner, exception)
+      request.set_header "action_dispatch.exception", wrapper.unwrapped_exception
+
       if wrapper.show?(request)
-        render_exception(request, wrapper)
+        render_exception(request.dup, wrapper)
       else
         raise exception
       end
@@ -44,7 +46,6 @@ module ActionDispatch
     private
       def render_exception(request, wrapper)
         status = wrapper.status_code
-        request.set_header "action_dispatch.exception", wrapper.unwrapped_exception
         request.set_header "action_dispatch.original_path", request.path_info
         request.set_header "action_dispatch.original_request_method", request.raw_request_method
         fallback_to_html_format_if_invalid_mime_type(request)

actionpack/test/dispatch/executor_test.rb

@@ -119,6 +119,34 @@ class ExecutorTest < ActiveSupport::TestCase
     assert_equal requests_count - 1, completed
   end
 
+  def test_error_reporting
+    raised_error = nil
+    error_report = assert_error_reported do
+      raised_error = assert_raises TypeError do
+        call_and_return_body { 1 + "1" }
+      end
+    end
+    assert_same raised_error, error_report.error
+  end
+
+  def test_error_reporting_with_show_exception
+    middleware = Rack::Lint.new(
+      ActionDispatch::Executor.new(
+        ActionDispatch::ShowExceptions.new(
+          Rack::Lint.new(->(_env) { 1 + "1" }),
+          ->(_env) { [500, {}, ["Oops"]] },
+        ),
+        executor,
+      )
+    )
+
+    env = Rack::MockRequest.env_for("", {})
+    error_report = assert_error_reported do
+      middleware.call(env)
+    end
+    assert_instance_of TypeError, error_report.error
+  end
+
   private
     def call_and_return_body(&block)
       app = block || proc { [200, {}, []] }