rspec/rules/S6146/rule.adoc

== Why is this an issue?

There are several compilations options available for Visual Basic source code and ``++Option Explicit++`` defines compiler behavior for implicit variable declarations. Specifying ``++Option Explicit Off++`` will allow creating a variable by it's first usage. This behavior can lead to unexpected runtime errors due to typos in variable names.


``++Option Explicit++`` can be set in project properties or overridden in individual source files.


=== Noncompliant code example

[source,text]
----
Option Explicit Off ' Noncompliant

Module MainMod

    Public Sub DoSomething(First As String, Second As String)
        Parameter = Fist        ' New local variable "Fist" is created and assigned to new local variable "Parameter" instead of "First" argument.
        DoSomething(Parameter)
        Parametr = Second       ' "Second" argument is assigned to newly created variable "Parametr" instead of intended "Parameter".
        DoSomething(Parameter)  ' Value of "Parameter" is always Nothing
    End Sub

    Private Sub DoSomething(Parameter As String)
        ' ...
    End Sub

End Module
----


=== Compliant solution

[source,text]
----
Option Explicit On

Module MainMod

    Public Sub DoSomething(First As String, Second As String)
        Dim Parameter As String = First
        DoSomething(Parameter)
        Parameter = Second
        DoSomething(Parameter)
    End Sub

    Private Sub DoSomething(Parameter As String)
        ' ...
    End Sub

End Module
----


== Resources

* https://docs.microsoft.com/en-us/dotnet/visual-basic/language-reference/statements/option-explicit-statement[Visual Basic documentation - Option Explicit Statement]