issue_comments

Having tried this out I think it does need a raise_404() mechanism - which needs to be smart enough to trigger the default 404 handler without accidentally going into an infinite loop.

Actually don't need {{ raise_404("Museum not found") }} because we already have {{ custom_status(404) }}.

I'm going to cache the list_templates() result in memory. If you want to add a new template-defined route you will need to restart the server. I think that's acceptable.

These templates will need a way to raise a 404 - so that if the template itself is deciding if the page exists (for example using datasette-template-sql or the proposed datasette.get() method from #943 or the graphql() template function in https://github.com/simonw/datasette-graphql/issues/50) it can return a regular 404 page.

This can imitate the custom_redirect() function from https://docs.datasette.io/en/stable/custom_templates.html#custom-redirects: html+jinja {{ custom_redirect("https://github.com/simonw/datasette", 301) }} It could be as simple as this: {{ raise_404("Museum not found") }}

I created a template file called templates/pages/museums/{slug}.html and used the debugger to see if Jinja could see it. This worked: (Pdb) self.ds.jinja_env.list_templates() ['500.html', '_codemirror.html', '_codemirror_foot.html', '_description_source_license.html', '_footer.html', '_table.html', 'allow_debug.html', 'base.html', 'database.html', 'default:500.html', 'default:_codemirror.html', 'default:_codemirror_foot.html', 'default:_description_source_license.html', 'default:_footer.html', 'default:_table.html', 'default:allow_debug.html', 'default:base.html', 'default:database.html', 'default:index.html', 'default:logout.html', 'default:messages_debug.html', 'default:patterns.html', 'default:permissions_debug.html', 'default:query.html', 'default:row.html', 'default:show_json.html', 'default:table.html', 'forbidden.html', 'index.html', 'logout.html', 'messages_debug.html', 'pages/about.html', 'pages/museums/{slug}.html', 'patterns.html', 'permissions_debug.html', 'query.html', 'row.html', 'show_json.html', 'table.html'] The pages/museums/{slug}.html template is in that list.

Here's the implementation of that list_templates() method - it does some filesystem walking so it may be a bit expensive to run it on every request: https://github.com/pallets/jinja/blob/ca8b0b0287e320fe1f4a74f36910ef7ae3303d99/src/jinja2/loaders.py#L197-L212

But caching it would be pretty easy - either until the server is restarted or as an in-memory cache for a few seconds.