feature: Allow automatically setting `session` per file

[ianhi]

Is your feature request related to a problem? Please describe.

I'm hoping to run files with multiple interdependent code blocks. This can be achieved using session but doing so requires adding that to every code block.

Describe the solution you'd like

Add a config option to enable having a default session per source file.

Describe alternatives you've considered

Writing out the session on every code block, which is ok to do - this request is more a quality of life thing.

Additional context

[pawamoy]

Thanks for the feature request @ianhi.

Unfortunately, we don't have access to that information when executing code blocks. We don't know which file we're in. That's because Python-Markdown doesn't think in terms of files. Still, I can think of a way to make the current MkDocs page available as a global variable, but that will tie the feature to the MkDocs plugin, which is not ideal.

Since language supporting sessions already use a "default" session by default, I wonder if what you want here is simply a toggle to have sessions scoped to files, rather than the whole site build. This alternative would still be tied to the MkDocs plugin though, as we'd have to use MkDocs hooks to reset sessions between each file rendering 🤔