IIfSideEffect

Identifies Functions or Properties referenced by the TruePart(second argument) or FalsePart(third argument) of the IIf built-in function.

New This feature is currently only available in pre-release builds (or the xmldoc asset doesn’t yet exist on main!).

Inspection type: CodeQualityIssues

Default severity: Warning

Reasoning

All arguments of any function/procedure call are always evaluated before the function is invoked so that their respective values can be passed as parameters. Even so, the IIf Function's behavior is sometimes mis-interpreted to expect that ONLY the 'TruePart' or ONLY the 'FalsePart' expression will be evaluated based on the result of the first argument expression. Consequently, the IIf Function can be a source of unanticipated side-effects and errors if the user does not account for the fact that both the TruePart and FalsePart arguments are always evaluated

Quick-Fixes

The following quick-fixes are available for this inspection:

  • IgnoreOnce: Adds an '@Ignore annotation to ignore a specific inspection result. Applicable to all inspections whose results can be annotated in a module.
  • IgnoreInModule: Adds an '@IgnoreModule annotation to ignore a inspection results for a specific inspection inside a whole module. Applicable to all inspections whose results can be annotated in a module.

Examples

Each example is a self-contained MCVE showing the feature in a single specific scenario.

Standard Module
Named Module1 by default, these are general-purpose standard procedural modules.
Class Module
Named Class1 by default, these modules define the default interface for an object of that type.
Predeclared Class
A class module with its VB_PredeclaredId attribute set to True (with or without a @PredeclaredId annotation).
Interface Module
Abstract interfaces are class modules (with or without an @Interface annotation) whose default interface is not a class type intended to be instantiated.
UserForm Module
A predeclared class with a design-time visual designer using the MSForms UI framework.
Document Module
Owned by the host application, these class modules belong to the host document and may handle various events fired by the host application.

The following code should trigger this inspection:

MyModule

Private divideByZeroAttempts As Long
Public Function DoSomeDivision(ByVal dividend As Long, ByVal divisor As Long) As Double
    'IIf will always result in an error with or without valid inputs.
    DoSomeDivision = IIf(divisor > 0, GetQuotient(dividend, divisor), DivideByZeroAttempted())
End Sub
Private Function GetQuotient(ByVal dividend As Long, ByVal divisor As Long) As Double
    ValidDivision = CDbl(dividend / divisor)
End Function
Private Function DivideByZeroAttempted() As Double
    DivideByZeroAttempted = 0#
    divideByZeroAttempts = divideByZeroAttempts + 1
    Err.Raise vbObjectError + 1051, "MyModule", "Divide by Zero attempted"
End Function

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