Many types now missing Debug implementations in v0.29

[qdot]

Similar to #1391, tried to compile https://github.com/deviceplug/btleplug with no changes, got a bunch of places where we expect Debug implementations that are now missing with no code changes other than updating from v0.28.

error[E0277]: `GattCommunicationStatus` doesn't implement `std::fmt::Debug`
  --> src\winrtble\ble\characteristic.rs:69:67
   |
69 |                 format!("Windows UWP threw error on write: {:?}", result).into(),
   |                                                                   ^^^^^^ `GattCommunicationStatus` cannot be formatted using `{:?}` because it doesn't implement `std::fmt::Debug`
   |
   = help: the trait `std::fmt::Debug` is not implemented for `GattCommunicationStatus`
   = note: this error originates in the macro `$crate::__export::format_args` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0277]: `GattReadResult` doesn't implement `std::fmt::Debug`
  --> src\winrtble\ble\characteristic.rs:88:66
   |
88 |                 format!("Windows UWP threw error on read: {:?}", result).into(),
   |                                                                  ^^^^^^ `GattReadResult` cannot be formatted using `{:?}` because it doesn't implement `std::fmt::Debug`
   |
   = help: the trait `std::fmt::Debug` is not implemented for `GattReadResult`
   = note: this error originates in the macro `$crate::__export::format_args` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0277]: `BluetoothConnectionStatus` doesn't implement `std::fmt::Debug`
  --> src\winrtble\ble\device.rs:47:42
   |
47 |                     trace!("state {:?}", sender.ConnectionStatus());
   |                                          ^^^^^^^^^^^^^^^^^^^^^^^^^ `BluetoothConnectionStatus` cannot be formatted using `{:?}` because it doesn't implement `std::fmt::Debug`
   |
   = help: the trait `std::fmt::Debug` is not implemented for `BluetoothConnectionStatus`
   = note: this error originates in the macro `format_args` (in Nightly builds, run with -Z macro-backtrace for more info)

[qdot]

Ok I just saw in the v0.29 Changelog that Debug is no longer implemented by default in the new generator. Is there a flag to turn that back on somehow if needed?

[kennykerr]

Yes, the Debug trait is not provided by the new bindgen crate. Is that something that I should preserve? I'm trimmed it down to the basics as far as traits go as it all adds up to the expense of building with the windows crate but it would help to understand whether this is something that is just a convenience or is really needed.

[poliorcetics]

Deriving Debug on pretty much everything is something we do by default internally, it would be really nice to have it for windows types, manually implementing it is cumbersome.

[roblabla]

IMO, Debug should really be implemented on everything. It is part of the Rust API Guidelines: https://rust-lang.github.io/api-guidelines/debuggability.html?highlight=debug#all-public-types-implement-debug-c-debug and are a huge help when debugging issues, as they allow quickly printing the contents of a structure. The problem with not implementing debug is that it causes a cascade of problems: Structures containing windows-rs structs will themselves not be able to derive debug, neither will their parent structures, etc... This makes working with crates that don't implement debug incredibly painful.

I really hope that this is reverted, or at least that a compile-time option to enable Debug is provided.

[kennykerr]

Good feedback. Much appreciated.

[qdot]

Thanks for being so responsive on this! :)