Hide non essential parts of "Network" snippets by default

[budziq]

Updated net.md to hide error_chain boilerplate by default
it can be exposed by selecting the "expand button"
The expand button is no longer hidden

This is connected to https://github.com/brson/rust-cookbook/issues/106
@dtolnay please check if net.md and decide if such approach is acceptable

• Please note no other section was updated as this is only a demo for the moment ;)

[dtolnay]

Thanks! This is great.

Looks like the hidden parts are awkwardly indented by one space when visible. Is that something we can fix or a mdBook bug?

Is // fn main() required?

[budziq]

both indentation and // fn main() are problems with mdbook:

• the hidden code has to have at least one space from # char or the doctests will not compile. Possibly this could be solved in mdbook
• // fn main() - is a workaround for mdbook inserting its own boilerplate

#![allow(unused_variables)]
fn main() {
...

around playpen if it does not find string fn main() in the example (due to quick_main!)

[dtolnay]

Let's fix both of those in mdBook before merging this. I think the solutions are:

• It should treat # the same way rustdoc does. That means no awkward one space indent.
• Do not insert boilerplate if there is a quick_main!.

[dtolnay]

I filed https://github.com/azerupi/mdBook/issues/281 and https://github.com/azerupi/mdBook/issues/282 to follow up on the mdBook fixes.

[budziq]

@dtolnay I made (hopefully nonidiotic) PR's for both of these issues.
For what is worth the indentation problem can be solved by locally patching the book.js
but I would strongly prefer for this problem to be solved in mdbook.

[budziq]

Rebased and cleaned up the commit. As both problems are now fixed in upstream mdbook I would wait for the next mdbook release (0.0.22) @azerupi

[budziq]

@dtolnay mdbook has released a version (0.0.22) with fixes for both blockers.
I have rebased the PR for your consideration.

If the idea and this PR is ok then I'll gladly update rest of the examples.

[dtolnay]

Thanks!