Validating a Notes formula from LotusScript

View member feedback to this tip.

This code can be used to validate a Notes formula before using it in an Evaluate() statement or in a call to db.Search(). It will also tell you the offset of any error. I use it in a Web interface to create customized reports to mimic Domino Designer's "Check formula" functionality. It uses functions in the Notes DLL, as documented in the Lotus C API, example code support Win32 (look here for help on using the same code on another platform).

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Here's an example:

Dim sFormula as String

sFormula = {SELECT FORM = 
"MyForm" & @IsAvailable(Status_T)}

iRC = 
CheckSelectionFormulaValid
(sFormula)
if iRC(0) = NO_ERROR Then
     Print "Formula is valid!"
Else
     Print "Formula error: " & 
GetAPIError(iRC(0))
     Print "Error starts at character: " 
& Cstr(iRC(1)) & " and ends at 
character: " & Cstr(iRC(2))
End If

Removing the "@" from the @IsAvailable keyword should give you those results:

Formula error: @Function or operator expected, or @Function does not require an argument. Error starts at character 47 and ends at character 47, which is the last parentheses.

Const NULLHANDLE = 0
Const NO_ERROR = 0
Const ERR_FORMULA_COMPILATION 
= &h500 + 1

Declare Function NSFFormulaCompile 
Lib "nnotes.dll" ( _
Byval FormulaName As Long, _
Byval FormulaNameLength As Integer, _
Byval FormulaText As Lmbcs String, _
Byval FormulaTextLength As Integer, _
rethFormula As Long, _
retFormulaLength As Integer, _
retCompileError As Integer, _
retCompileErrorLine As Integer, _
retCompileErrorColumn As Integer, _
retCompileErrorOffset As Integer, _
retCompileErrorLength As Integer _
) As Integer

Declare Sub OSMemFree Lib "nnotes.dll" 
(Byval hHandle As Long)

Declare Function OSLoadString Lib 
"nnotes.dll" ( _
Byval hmodule As Long, _
Byval status As Integer, _
Byval s As String, _
Byval slen As Integer _
) As Integer

' =============================
===============================
====================
' CheckSelectionFormulaValid - 
This function uses the Lotus 
C API to check the
syntax of a Notes formula.
'
' Return Value: Variant - A 3 elements
 array containing:
' Index 0 - The compilation error code 
or NO_ERROR (0) if valid
' Index 1 - The compilation error offset 
in formula or NO_ERROR if valid 
' Index 2 - The compilation error length 
or NO_ERROR if valid
'
' Note: The compilation error code at 
Index 0 can then be passed to GetAPIError
() to get more info about the error.
' =============================
==============================
=====================
Function CheckSelectionFormulaValid
(sFormula) As Variant
 
 Dim iError As Integer
 Dim hFormula As Long
 Dim wFormulaLen As Integer
 Dim iCompileError As Integer
 Dim iCompileErrorLine As Integer
 Dim iCompileErrorColumn As Integer
 Dim iCompileErrorOffset As Integer
 Dim iCompileErrorLength As Integer
 Dim iArray(2) As Integer
 
 iError = NSFFormulaCompile(0, 0, _
 sFormula, _
 Len(sFormula), _
 hFormula, _
 wFormulaLen, _
 iCompileError, _
 iCompileErrorLine, _
 iCompileErrorColumn, _
 iCompileErrorOffset, _
 iCompileErrorLength)
 
 If hFormula <> NULLHANDLE Then
  Call OSMemFree(hFormula)
 End If
 
 If iError = ERR_FORMULA_COMPILATION
 Then
  iArray(0) = iCompileError
  iArray(1) = iCompileErrorOffset
  iArray(2) = iCompileErrorLength
  CheckSelectionFormulaValid = iArray
 Else
  iArray(0) = NO_ERROR
  iArray(1) = NO_ERROR
  iArray(2) = NO_ERROR
  CheckSelectionFormulaValid = iArray
 End If
 
End Function
' ===============================
================================
=================
' GetAPIError - This function uses the 
Lotus C API to return a Notes error's
text message.
'
' Return Value: String - The text associated 
with the Notes API error code.
' ================================
=================================
===============
Function GetAPIError(iErrorCode As Integer) 
As String
 
 Dim iRetVal As Integer
 Dim sError As String * 1024
 
 sError = String(1024, 0)
 
 iRetVal = OSLoadString(0&, iErrorCode,
 sError, 1023)
 
 If iRetval <> 0 Then
  GetApiError = Left$(sError, iRetVal)
 End If

End Function

MEMBER FEEDBACK TO THIS TIP

I think this is a great tip! The writer suggested using it prior to any Evaluate() call. I suggest using it to debug any @Formulas you are working with during routine development.

I created a simple form that I put in my utilities database and will use it all the time. The form has one field and one action button. Put something like this in the button:

Sub Click( Source As Button )
 
 Dim ws As New NotesUIWorkspace
 Dim uiDoc As NotesUIDocument
 Set uiDoc = ws.CurrentDocument
  
 iRC = CheckSelectionFormulaValid
( uiDoc.FieldGetText("testFormula" ) )
 
 If iRC(0) = NO_ERROR Then
  Msgbox "Formula is valid!"
 Else
  Print "Formula error: " & 
GetAPIError(iRC(0))
  Print "Error starts at character: " & 
Cstr(iRC(1)) & " and ends at character: " 
& Cstr(iRC(2))
  
  Msgbox "Error starts at character: " & 
Cstr(iRC(1)) & " and ends at character: " 
& Cstr(iRC(2)), , _
  "Formula error: " & GetAPIError(iRC(0))
  
 End If
 
End Sub

You may also want to check out another tip, called Formula debugger. It's very similar to the tip listed above.

—Doug J.

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