Error management in VBAToolKit

While coding VBAToolKit, we thought it could be nice if errors could work their way up the stack, instead of popping a MsgBox with a low-level error message that users won't understand.

To implement this, we considered the fact that in a called function, an error raised in the error handler is actually passed to the caller function.

For example, the following code :

Public Sub caller()  
    On Error GoTo callerErr  
    called
callerErr:  
    MsgBox "Error " & err.Number & " in " & err.Source & " : " & err.Description  
End Sub


Public Sub called()
    On Error GoTo calledErr
    err.Raise 3600,"Sub 'called'", "dummy error"
calledcalledErr:
    err.Raise err.Number, err.Source, err.Description
    Exit Sub
End Sub

will pop a MsgBox displaying "Error 3600 in 'Sub called' : dummy error" when running caller .

It can work with every number of levels.

This example with 3 levels will pop the very same MsgBox :

Public Sub caller()  
    On Error GoTo callerErr      
    called   
callerErr:  
    MsgBox "Error " & err.Number & " in " & err.Source & " : " & err.Description  
End Sub


Public Sub called()
    On Error GoTo calledErr
    calledcalled
calledErr:
    err.Raise err.Number, err.Source, err.Description
    Exit Sub
End Sub


Public Sub calledcalled
    On Error GoTo calledcalledErr
    err.Raise 3600,"Sub 'calledcalled'", "dummy error"
calledcalledErr:
    err.Raise err.Number, err.Source, err.Description
    Exit Sub
End Sub

This allows the filtering of errors rising from the depths of the code to produce custom errors messages relevant to the user.

For example, the code :

Public Sub caller()  
    On Error GoTo callerErr      
    called   
callerErr:  
    MsgBox "Error " & err.Number & " in " & err.Source & " : " & err.Description  
End Sub


Public Sub called()
    On Error GoTo calledErr
    calledcalled
calledErr:
    err.Raise 6666, "Sub 'called'", "Something went wrong."
    Exit Sub
End Sub


Public Sub calledcalled
    On Error GoTo calledcalledErr
    err.Raise 3600,"'Sub calledcalled'", "Cryptic error message"
calledcalledErr:
    err.Raise err.Number, err.Source, err.Description
    Exit Sub
End Sub

will display to the user "Error 6666 in 'Sub called' : Something went wrong.".

Please note that this mechanism has not yet been implemented in the entire project.