Should Moose check block-restriction in FEProblemBase::duplicateVariableCheck

[jmeier]

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Question

Dear Moose-Community,

Many of my Moose models consit of several subdomains / blocks while not all Variables and/or AuxVariables live on all subdomains/blocks. When setting up my models, I have repeatedly had the problem that variables/aux variables are required by different kernels, but were restricted to different blocks (which is of course a mistake on my part and/or other problems e.g. #28308).
On the other hand, Moose checks in FEProblemBase::duplicateVariableCheck whether the variable already exists and is of the same type and thus avoids creating it twice. Unfortunately, Moose does not check that the block restriction is identical. Moose often outputs an error in the further modelling if the block-restriction was not identical, but the error messages often only indirectly indicating the underlying problem.

It would have been good if Moose had pointed out the problem of the inconsistent block restriction of the variables/aux variables more directly: Therefore, should Moose check block-restriction in FEProblemBase::duplicateVariableCheck and warn/error?
If so, I would like to collect your thoughts on whether this check should always be carried out or only on request.

moose/framework/src/problems/FEProblemBase.C

Lines 2843 to 2844 in 1926a67

	if (duplicateVariableCheck(var_name, fe_type, /* is_aux = */ true))
	return;

moose/framework/src/problems/FEProblemBase.C

Lines 2540 to 2551 in 1926a67

	if (curr_sys_ptr->hasVariable(var_name))
	{
	const Variable & var =
	curr_sys_ptr->system().variable(curr_sys_ptr->system().variable_number(var_name));
	if (var.type() != type)
	mooseError(error_prefix,
	"Variable with name '",
	var_name,
	"' already exists but is of a differing type!");
	return true;
	}

[GiudGiud]

Hello

If you want the message to be more verbose and give more information (such as the block restriction) then that would work for us. Already it says "different type" but it would help the user to say which types are involved

However we can't really allow the check to let two "identical" variables be added without some serious checking. There are many variable parameters, we would have to check them all, not just the block restriction.

Guillaume

[jmeier]

I'll try to prepare an PR.