Use an enum class, it's strongly typed but the compiler just treats it as an integer

telling the user to check their manual

• So I made an API for a DB.
• The client was full on using Qt Framework with Qt Creator, so I also made it in Qt.
• I return QSqlError in my functions and point the user to QSqlError documentation in Qt
  • I even show them that they can press F1 at any time in Qt Creator to get the help page
• Months later, client engineers raise problem with senior management that they don't have a bool return value (I am sitting 10m away in the same room as the client. Senior management is in another state)
• I press F1 on their computer and show the user bool QSqlError::isValid()
  • Note again, that all client devs at this point, have been using Qt, years before I enter.
• User says they don't have a bool result.
  • I open their code and show them how to use isValid() in an if statement.
• User puts a requirement for custom functions returning bool
  • I make more functions for that
• Months later, I get a bug report, stating that the deleteDocument function is deleting the document but returning false.
• I check the code

API::deleteDocument(docId);

if (API::deleteDocument(docId))
{
  // output to UI
}

Yes, they called deleteDocument on the same ID twice.

BTW, I did create a manual with usage examples.

A few months later, a senior engineer on the client side checks their code and tells me to throw exceptions for everything, because half of the time, the user-devs are not checking the QSqlError return values.

[[nodiscard]]

From what I remember, that gives a warning an not an error.
The clients' code already has >400 warnings^[edit: fixed wrong word] on every build. They won't care

as long as people are logging pertinent information sure. but I've had the misfortune of working with plenty of programs that return just an error code that means 'something went wrong initialising subsystem X' and left it all to the user to figure out what exactly went wrong, with files and where in those files etc. etc.

For fuck's sake people, stop localizing your error messages.

At work we literally just went through this yesterday, just with folly::Expected. A new guy joined the team and wanted to propose we update how we handle errors.