Breakage caused by PinStatus and PinMode types

Start with api/Common.h and reproduce the reported compilation failures using the Keypad examples and the digitalWrite(13, !digitalRead(13)) case. Review the linked discussions and related issue to understand the compatibility decision; this issue is done only when the project reaches and documents a decision, with affected compatibility behavior verified.

This project changes LOW, HIGH, INPUT, INPUT_PULLUP, and OUTPUT from macros to enums:
https://github.com/arduino/ArduinoCore-API/blob/e1eb8de126786b7701b211332dda3f09aa400f35/api/Common.h#L10-L23

I'm concerned that this will cause breakage of a significant amount of existing code.

An example is the popular Keypad library. Compilation of both the original library and the version in Library Manager fails once this change is made.

In file included from E:\electronics\arduino\libraries\Keypad-master\examples\HelloKeypad\HelloKeypad.ino:10:0:

E:\electronics\arduino\libraries\Keypad-master\src/Keypad.h: In member function 'virtual void Keypad::pin_write(byte, boolean)':

E:\electronics\arduino\libraries\Keypad-master\src/Keypad.h:81:81: error: cannot convert 'boolean {aka bool}' to 'PinStatus' for argument '2' to 'void digitalWrite(pin_size_t, PinStatus)'

  virtual void pin_write(byte pinNum, boolean level) { digitalWrite(pinNum, level); }

This commonly used code will also now fail:

digitalWrite(13, !digitalRead(13));  // toggle pin 13

toggle:2:36: error: cannot convert 'bool' to 'PinStatus' for argument '2' to 'void digitalWrite(pin_size_t, PinStatus)'

   digitalWrite(13, !digitalRead(13));  // toggle pin 13

I understand that the root cause of these errors is bad code and that any code which followed best practices will have no problems with this change. However, I fear there is a lot of bad code in widespread use that currently works fine. In the case of the Keypad library, it is unlikely it can even be fixed since Chris--A has gone AWOL. I'm sure there are other such abandoned projects.

I do like the spirit of this change (though lumping CHANGE, FALLING, and RISING into PinStatus is questionable). I'm open to being convinced that it's worth the breakage and, if so, I'm willing to help ease the transition by providing user support and submitting PRs to fix broken code. I just think this warrants some consideration before ArduinoCore-API goes into more widespread use.

Additional context

Some previous discussion on the topic:

• http://forum.arduino.cc/index.php?topic=455579 (from here onward)
• https://forum.arduino.cc/index.php?topic=584322
• http://forum.arduino.cc/index.php?topic=602250
• https://forum.arduino.cc/index.php?topic=621429
• https://forum.arduino.cc/index.php?topic=627883.msg4319254#msg4319254
• https://forum.arduino.cc/index.php?topic=659624
• https://github.com/arduino/ArduinoCore-megaavr/issues/68

Related

• https://github.com/arduino/ArduinoCore-mbed/issues/1107