The standard library version of an `RwLock` may get poisoned if a thread
panics that holds a write lock. The `RwLock` from parking_lot [1] does
not get poisoned it instead released the lock on a panic. This allows us
to simplify the `ProgressOutput` API since it no longer returns any
errors. No more panics can occur on `ProgressOutput::drop()`. The
`Error` enum can thus be simplified as well because there is no need to
convert `PoisonErrors` anymore.
[1] https://github.com/Amanieu/parking_lot
This will fix the broken spinners that indicate steps which are
currently in progress. To achieve this the behavior of the progressbar
helper had to be adjusted.
The multibar does not work while a child process is run with
`std::process::Command`. Using multiple spinners without a multibar is
problematic as well because emitting warnings, infos and errors while a
single spinner is active will duplicate the spinners message. The
spinner will also absorb the last warning/error/info. Instead of
publishing warnings, errors and infos immediately they will now be
cached and only output when the current spinner finishes.
To make sure we can output all warnings to the user ProgressBars are no
longer exposed to the caller. Instead the active spinner will be
finished implicitly when a new spinner is allocated with the `message()`
function. Instead of relying on the `done()` function to be called the
progressbar now implements the `Drop` trait which will finish the last
spinner automatically.
Unfortunately, this introduces members that have to be mutable. To not
have to deal with mutable ProgressOutput all over the place the members
were put inside an RwLock. This allows us to use ProgressOutput from
inside multiple threads to emit warnings and errors.
Mackiovello