Code validity check

[Kobzol]

I'm opening this for discussion. What do you think about validator that would check that code inside Python blocks is valid (can be compiled, does not raise any Exceptions when executed)? It could try to compile/execute the code and warn the user during compilation if the code is invalid.

If the code should be invalid (e.g. uses undefined variables, raises exceptions), then it could be marked somehow in Markdown (e.g. ```python,can-fail). Previous code blocks could also be automatically appended to the block that is being compiled to provide context for variable names.

The motivation is to avoid errors like this.

This is obviously quite dangerous, so it would have to be executed inside Arca or something like that.

[encukou]

It can be made opt-in, either course-wide or for individual lessons.
It would be nice to try this with existing materials and see how much they need to be changed. I don't have too much hope – I'm not using "literate programming". Not all code that the student needs to write is shown in code blocks.