An error during template rendering could throw the server into an infinite loop

[Kixiron]

We have a call to ctry! within WebPage::into_response, which means that if the rendering of a template fails we call WebPage::into_response on an ErrorPage. I'm not really sure what conditions would have to line up in order for it to happen, but it's possible that the server could get into an infinite loop of rendering and failing templates which wouldn't be good

[jyn514]

That could only happen if the error page itself fails to render. Since we test the error page, I don't think this is an issue in practice.

[Kixiron]

Agreed, it's super unlikely to happen, but it is a possible footgun

[jyn514]

Yup, you're right, this sends the server into an infinite loop:

diff --git a/templates/error.html b/templates/error.html
index e7685ec..6a1b855 100644
--- a/templates/error.html
+++ b/templates/error.html
@@ -9,4 +9,5 @@
     <div class="description">
         {{ message | default(value="") }}
     </div>
+    {{ oops }}
 {%- endblock header -%}

and then fetching /not_here.

[jyn514]

I think it might honestly better to just panic in that case; that way it only crashes a single request instead of locking up the server. We test errors anyway so it shouldn't ever happen in prod.