Limit playground references to tests

[Arthur-Milchior]

The system used by https://google.github.io/comprehensive-rust/exercises/day-1/book-library.html allows to execute code directly in the book. So playground references became useless. If I got it wrong, it would be nice to at least explain why it’s not sufficient to edit and run in this book.

The only exception I saw is in the test setting. Playground allows to run tests. In this case, I believe adding a sentence warning that tests are ignored by this book running system means that we really must use the playground and ignore the "run" button provided by the book

[mgeisler]

Hi @Arthur-Milchior,

If I got it wrong, it would be nice to at least explain why it’s not sufficient to edit and run in this book.

Editing in the inline-playgrounds works — that was how the course worked for the first time I ran it internally. However, there is a crucial problem: the inline-playground loses its state as soon as you navigate away from the page. A single Left-Arrow press with focus outside of the text box is enough to lose everything. So that lead to a lot of sadness in the trial run... tears were shed (almost) :smile:

Copying the text to the "real" stateful playground works better. It also shows stderr right away: the inline-playground only shows stderr if compilation is unsuccessful. That's something I would like to fix in upstream mdbook so that stderr is shown always. That would allow me to use the dbg! macro throughout and save a lot of typing.

[mgeisler]

I could perhaps create a document outside the course which mentions these quirks...

[mgeisler]

We can now point this out in the speaker notes: #118. The problem with stderr is still there, but we'll probably have to fix this upstream.