refactor: use concrete error type

[2bndy5]

Concrete Error type

Changes the Esb* traits to require a new trait RadioErrorType.

rf24-rs/crates/rf24-rs/src/radio/prelude.rs

Line 457 in da90c7a

pub trait EsbRadio: RadioErrorType {

In the RadioErrorType trait, there is an associated Error type.

rf24-rs/crates/rf24-rs/src/radio/prelude.rs

Lines 15 to 18 in da90c7a

	/// A trait to alias hardware related errors about the radio.
	pub trait RadioErrorType {
	type Error;
	}

Then, the RadioErrorType trait is implemented for the RF24 struct.

rf24-rs/crates/rf24-rs/src/radio/rf24/mod.rs

Lines 59 to 66 in da90c7a

	impl<SPI, DO, DELAY> RadioErrorType for RF24<SPI, DO, DELAY>
	where
	SPI: SpiDevice,
	DO: OutputPin,
	DELAY: DelayNs,
	{
	type Error = Nrf24Error<SpiError, OutputPinError>;
	}

Subsequent required implementations

The ? operator used to propagate Result::Err needed an explicit forwarding mechanism for hardware-related errors, namely embedded_hal::digital::ErrorKind as OutputPinError and embedded_hal::spi::ErrorKind as SpiError.

rf24-rs/crates/rf24-rs/src/radio/rf24/mod.rs

Lines 47 to 57 in da90c7a

	impl From<SpiError> for Nrf24Error<SpiError, OutputPinError> {
	fn from(value: SpiError) -> Self {
	Nrf24Error::Spi(value)
	}
	}
	impl From<OutputPinError> for Nrf24Error<SpiError, OutputPinError> {
	fn from(value: OutputPinError) -> Self {
	Nrf24Error::Gpo(value)
	}
	}

This allows automatic categorization of the error encountered using our Nrf24Error enum.

Advantages

This convoluted approach

• allows the radio implementation to choose their own error type (useful if/when I get around to implementing ESB API on nRF5x chips).
• better prepares for implementing the network layers since only the radio type needs to be known at compile time.
• provides better error messages when debugging panics
• unifies the error type returned by various Esb* traits' fallible functions. Previously, each trait had it's own associated error type which didn't bode well for implementing different radio hardware.

Using dev branch of embedded-hal-mock fork

There were a few lines about forward error types into our own Nrf24Error enum (impl From<T> -- see above).
I opened a couple issues to hopefully resolve this upstream in the mock library we're using for unit tests:

• add with_error() for SPI Transaction dbrgn/embedded-hal-mock#128
  • resolved by add: Mock SPI errors dbrgn/embedded-hal-mock#131
• use embedded_hal::digital::ErrorKind for mocked digital pins dbrgn/embedded-hal-mock#129 (would be considered a breaking change though)
  • resolved by refactor!: eh1::digital use embedded_hal::digital::ErrorKind dbrgn/embedded-hal-mock#132

For now, I'll be using my fork's dev branch until these patches are accepted and deployed upstream.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (39d8287) to head (da90c7a).
⚠️ Report is 35 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main       #42   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           22        22           
  Lines         3154      3175   +21     
=========================================
+ Hits          3154      3175   +21     

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