Getting stack trace of error in LotusScript

Java has a wonderful method called printStackTrace which prints out the entire stack trace in case of exception. Unfortunately LotusScript does not have any similar functionality. But we can use On Error statement to reproduce this functionality.

Sub Sub1
    On Error Goto ErrorHandler

    'Some code

    Call Sub2()

    'Some more code

    Exit Sub
ErrorHandler:
    errorStack = errorStack & Chr(13) & "Sub Sub1 > Error: " & Error$ & " Err: " & Err & " Erl: " & Erl
End Sub

Sub Sub2
    On Error Goto ErrorHandler

    Call Sub3()

    Exit Sub
ErrorHandler:
    errorStack = errorStack & Chr(13) & "Sub Sub2 > Error: " & Error$ & " Err: " & Err & " Erl: " & Erl
End Sub

Sub Sub3
    On Error Goto ErrorHandler

    'LOTS
    'OF
    'CODE

    Call doc.ReplaceItemValue("test", "test") 'Error statement

    Exit Sub
ErrorHandler:
    errorStack = errorStack & Chr(13) & "Sub Sub3 > Error: " & Error$ & " Err: " & Err & " Erl: " & Erl
End Sub

So you have three sub routines Sub1, Sub2 and Sub3, with Sub1 calling Sub2 and Sub2 calling Sub3. In Sub3 there is an statement which will throw error. All the three sub routines have error handlers and none of them have Exit Sub statement so that the error drops from Sub3 to Sub2 to Sub1. All the errors are stored in global string variable errorStack.

Lets say you call Sub1 from click of button which has this code:

On Error Goto ErrorHandler

    Call Sub1()

    Exit Sub
ErrorHandler:
    errorStack = errorStack & Chr(13) & "Error: " & Error$ & " Err: " & Err & " Erl: " & Erl
    Msgbox errorStack
    Exit Sub

So now when you click on the button you will get a complete trace of the error with this message:

Sub Sub3 > Error: Object variable not set    Err: 91    Erl: 8
Sub Sub2 > Error: No RESUME    Err: 19    Erl: 4
Sub Sub2 > Error: No RESUME    Err: 19    Erl: 6
Button click > Error: No RESUME    Err: 19    Erl: 4

Make sure you add Exit Sub statement after displaying the error stack other wise you will get No RESUME error after showing the stack trace. This is a very simple example, but in case Sub3 is being called from multiple other sub routines then it can help in tracing exact path of error.