issue_comments

I'm going to rename that to template variable from select_templates to templates_considered too.

I'd like to do this all in the datasette.render_template() method to ensure it's available to plugins as well, not just core code that uses the BaseView class.

This code is the problem: https://github.com/simonw/datasette/blob/d3e9b0aecb6f8e9b2befd9c654ccb7ce852db3e7/datasette/views/base.py#L114-L133

I think I'll fix this by moving the select_templates mechanism into datasette.render_templates().

It wouldn't be a disaster if template-loading plugins were unable to hook into the /{slug1}/{slug2}.html custom page mechanism, since plugins can define their own pages already using register_routes().

Another option: the first version of the plugin hook could accept only the template filename. Subsequent releases could add more arguments, since Pluggy allows new arguments to be added without breaking backwards compatibility.

So maybe this should be a register_template_loader mechanism that returns a Jinja loader after all? That would mean that only the template filename could be used as the input to the plugin, which doesn't seem as useful as emulating the extra_template_vars() interface.

Also consider that DatasetteRouter uses .list_templates() to gather together {slug}.html style templates for the custom page templates mechanism: https://github.com/simonw/datasette/blob/976e5f74aae1fa0d406df6691dc8b5feeebe8788/datasette/app.py#L949-L967

For that to work with the new plugin hook, custom template providing plugins will need a way to provide a list of templates that they know about.

Almost all of the core template loading happens in the BaseView.render method: https://github.com/simonw/datasette/blob/976e5f74aae1fa0d406df6691dc8b5feeebe8788/datasette/views/base.py#L114-L133

The one exception is the 404 handling code here: https://github.com/simonw/datasette/blob/976e5f74aae1fa0d406df6691dc8b5feeebe8788/datasette/app.py#L1034-L1042

Alternative plugin hook idea: python @hookspec def load_template(template, database, table, columns, view_name, request, datasette): "Load the specified template, returning the template code as a string" Imitating the existing extra_template_vars family of hooks: https://docs.datasette.io/en/stable/plugin_hooks.html#extra-template-vars-template-database-table-columns-view-name-request-datasette

Maybe the template loader can optionally return some extra context to pass to the template. That could be used to solve the templates considered comment.

When loading a template the filename is required, but you can optionally also send a set of extra arguments which the template loader can take into consideration.

A better version of this hook would be passed the database, table and query name depending on what was being rendered.

This would require some re-thinking of how core templates are loaded, especially since I would want the templates considered comment to continue working.

I'll build this in conjunction with a plugin that supports editing templates stored in SQLite.

Maybe register_template_loader(datasette) which returns an object which is added in at the beginning of the list passed to ChoiceLoader here.

Relevant code: https://github.com/simonw/datasette/blob/d0cc6f4c32e1f89238ddec782086b3122f445bd4/datasette/app.py#L288-L311