Clear & ClearAll Single Instace Codeunit

[ChrisBlankDe]

Since Clear(SingleInstanceCodeunit); or ClearAll(); in a single Instance codeunit does not work as expected (does not clear global variables) LinterCop should show a warning.

[Arthurvdv]

Good point and thank you for raising a discussion here.

If I understand correctly these are the both cases you're referring to?

codeunit 50100 MyCodeunit
{
    procedure DoSomething()
    var
        MySingleInstanceCodeunit: Codeunit MySingleInstanceCodeunit;
    begin
        // Raise a LC00xx rule here
        Clear(MySingleInstanceCodeunit);
    end;
}

codeunit 50101 MySingleInstanceCodeunit
{
    SingleInstance = true;

    procedure ClearAllTheVariables()
    begin
        // Raise a LC00xx rule here
        ClearAll();
    end;
}

Do we need to verify if there are any global variables defined in the codeunit, or always raise the rule?

[Arthurvdv]

Did some more testing, and it's a bit more complicated it seems.

codeunit 50100 MyCodeunit
{
    var
        MySingleInstanceCodeunit: Codeunit MySingleInstanceCodeunit;
        MyDocumentNumber: Code[20];

    procedure DoSomething()
    begin
        MyDocumentNumber := 'SomeRandomValue';
        MySingleInstanceCodeunit.Set(MyDocumentNumber);
        Message('1. Value in the MyDocumentNumber is ''%1''.', MyDocumentNumber);
        Message('2. Value in the MySingleInstanceCodeunit is ''%1''.', MySingleInstanceCodeunit.Get());
        ClearAll();
        Message('3. Value in the MyDocumentNumber after a ClearAll() is now ''%1''.', MyDocumentNumber);
        Message('4. Value in the MySingleInstanceCodeunit after a ClearAll() is now ''%1''.', MySingleInstanceCodeunit.Get());
        Clear(MySingleInstanceCodeunit);
        Message('5. Value in the MySingleInstanceCodeunit after a Clear() is now ''%1''.', MySingleInstanceCodeunit.Get());
        MySingleInstanceCodeunit.ClearAllTheVariables();
        Message('6. Value in the MySingleInstanceCodeunit after a executing the ClearAllTheVariables() is now ''%1''.', MySingleInstanceCodeunit.Get());
    end;
}

codeunit 50101 MySingleInstanceCodeunit
{
    SingleInstance = true;

    var
        GlobalDocumentNumber: Code[20];

    procedure Set(NewDocumentNumber: Code[20])
    begin
        GlobalDocumentNumber := NewDocumentNumber;
    end;

    procedure Get(): Code[20]
    begin
        exit(GlobalDocumentNumber);
    end;

    procedure ClearAllTheVariables()
    begin
        ClearAll();
    end;
}

1. Value in the MyDocumentNumber is 'SOMERANDOMVALUE'.
2. Value in the MySingleInstanceCodeunit is 'SOMERANDOMVALUE'.
3. Value in the MyDocumentNumber after a ClearAll() is now ''.
4. Value in the MySingleInstanceCodeunit after a ClearAll() is now 'SOMERANDOMVALUE'.
5. Value in the MySingleInstanceCodeunit after a Clear() is now 'SOMERANDOMVALUE'.
6. Value in the MySingleInstanceCodeunit after a executing the ClearAllTheVariables() is now ''.

So in conclusion
A) Executing a Clear(MySingleInstanceCodeunit) should raise a warning when there are global variables defined inside the referencing codeunit.
B) Exectuing a ClearAll() in a object (page, codeunit, etc) which has local or global codeunit variables, where one of them is set as a SingleInstance, raise the rule.

Doubting on what to do with the global variable of the type record inside the referencing codeunits? And do we have a "inception situation" going on here? The referencing single instance codeunit has a global variable to another single instance codeunit and so on. This could lead to a point that the rule could get confusing?

codeunit 50100 MyCodeunit
{
    var
        MySingleInstanceCodeunit: Codeunit MySingleInstanceCodeunit;
        MySingleInstanceCodeunitWithOnlyGlobalRecords: Codeunit MySingleInstanceCodeunitWithOnlyGlobalRecords;

    procedure DoSomething()
    begin
        // Raise a LC00xx rule here (MySingleInstanceCodeunit is Single Instance ánd has non-Record type Global variables)
        Clear(MySingleInstanceCodeunit);

        // Do not raise a LC00xx rule here (MySingleInstanceCodeunitWithOnlyGlobalRecords is Single Instance, but doesn't have non-Record type Global variables)
        Clear(MySingleInstanceCodeunitWithOnlyGlobalRecords);

        // Raise a LC00xx rule here (MySingleInstanceCodeunit is Single Instance ánd has non-Record type Global variables)
        ClearAll();
    end;
}

codeunit 50101 MySecondCodeunit
{
    var
        MySingleInstanceCodeunitWithOnlyGlobalRecords: Codeunit MySingleInstanceCodeunitWithOnlyGlobalRecords;

    procedure DoSomething()
    begin
        // Do not raise a LC00xx rule here (MySingleInstanceCodeunitWithOnlyGlobalRecords is Single Instance, but doesn't have non-Record type Global variables)
        Clear(MySingleInstanceCodeunitWithOnlyGlobalRecords);

        // Do not raise a LC00xx rule here (MySingleInstanceCodeunitWithOnlyGlobalRecords is Single Instance, but doesn't have non-Record type Global variables)
        ClearAll();
    end;
}

codeunit 50102 MyThirthCodeunit
{
    var
        MySingleInstanceCodeunitWithAnotherSingleInstanceCodeunit: Codeunit MySingleInstanceCodeunitWithAnotherSingleInstanceCodeunit;

    procedure DoSomething()
    begin
        // Raise a LC00xx rule here (In the reference tree a reference to the MySingleInstanceCodeunit)
        Clear(MySingleInstanceCodeunitWithAnotherSingleInstanceCodeunit);

        // Raise a LC00xx rule here (In the reference tree a reference to the MySingleInstanceCodeunit)
        ClearAll();
    end;
}

codeunit 50103 MySingleInstanceCodeunit
{
    SingleInstance = true;

    var
        GlobalCustomerRec: Record Customer;
        GlobalDocumentNumber: Code[20];

    procedure Set(NewDocumentNumber: Code[20])
    begin
        GlobalDocumentNumber := NewDocumentNumber;
    end;

    procedure Set(NewCustomerRec: Record Customer)
    begin
        GlobalCustomerRec := NewCustomerRec;
    end;

    procedure Get(): Code[20]
    begin
        exit(GlobalDocumentNumber);
    end;

    procedure ClearAllTheVariables()
    begin
        // Do not raise a LC00xx rule here
        ClearAll();
    end;
}

codeunit 50104 MySingleInstanceCodeunitWithOnlyGlobalRecords
{
    SingleInstance = true;

    var
        GlobalCustomerRec: Record Customer;

    procedure Set(NewCustomerRec: Record Customer)
    begin
        GlobalCustomerRec := NewCustomerRec;
    end;

    procedure Get() Customer: Record Customer;
    begin
        exit(GlobalCustomerRec);
    end;

    procedure ClearAllTheVariables()
    begin
        // Do not raise a LC00xx rule here
        ClearAll();
    end;
}

codeunit 50105 MySingleInstanceCodeunitWithAnotherSingleInstanceCodeunit
{
    SingleInstance = true;

    var
        MySingleInstanceCodeunit: Codeunit MySingleInstanceCodeunit;
}

[Arthurvdv]

I've created an rule for this, and available in the prelease: #348