Allowing to define an array varible with component size one, refs ida…

…holab#19564

framework/include/actions/AddVariableAction.h

@@ -57,6 +57,15 @@ class AddVariableAction : public MooseObjectAction
   static std::string
   determineType(const FEType & fe_type, unsigned int components, bool is_fv = false);
 
+  /**
+   * Determines a variable type
+   * @param fe_type The FE type
+   * @param is_fv Whether or not the variable is use for finite volume
+   * @param is_array Whether or not the variable is an array variable
+   */
+  static std::string
+  variableType(const FEType & fe_type, const bool is_fv = false, const bool is_array = false);
+
 protected:
   /**
    * Initialize the action's member variables

framework/src/actions/AddVariableAction.C

@@ -133,8 +133,9 @@ AddVariableAction::init()
 
   // Determine the MooseVariable type
   bool is_fv = _moose_object_pars.get<bool>("fv");
+  bool is_array = (_components > 1 || _moose_object_pars.get<bool>("array")) ? true : false;
   if (_type == "MooseVariableBase")
-    _type = determineType(_fe_type, _components, is_fv);
+    _type = variableType(_fe_type, is_fv, is_array);
   if (is_fv)
     _problem->needFV();
 
@@ -224,11 +225,19 @@ AddVariableAction::createInitialConditionAction()
 
 std::string
 AddVariableAction::determineType(const FEType & fe_type, unsigned int components, bool is_fv)
+{
+  mooseDeprecated("AddVariableAction::determineType() is deprecated. Use "
+                  "AddVariableAction::variableType() instead.");
+  return variableType(fe_type, is_fv, components > 1);
+}
+
+std::string
+AddVariableAction::variableType(const FEType & fe_type, const bool is_fv, const bool is_array)
 {
   if (is_fv)
     return "MooseVariableFVReal";
 
-  if (components > 1)
+  if (is_array)
   {
     if (fe_type.family == LAGRANGE_VEC || fe_type.family == NEDELEC_ONE ||
         fe_type.family == MONOMIAL_VEC)

framework/src/systems/SystemBase.C

@@ -823,6 +823,13 @@ SystemBase::addVariable(const std::string & var_type,
     // The number returned by libMesh is the _last_ variable number... we want to hold onto the
     // _first_
     var_num = system().add_variables(var_names, fe_type, &blocks) - (components - 1);
+
+    // Set as array variable
+    if (parameters.isParamSetByUser("array") && !parameters.get<bool>("array"))
+      mooseError("Variable '",
+                 name,
+                 "' is an array variable ('components' > 1) but 'array' is set to false.");
+    parameters.set<bool>("array") = true;
   }
   else
     var_num = system().add_variable(name, fe_type, &blocks);

framework/src/variables/MooseVariableBase.C

@@ -62,6 +62,10 @@ MooseVariableBase::validParams()
                                      "Specifies a scaling factor to apply to this variable");
   params.addParam<bool>("eigen", false, "True to make this variable an eigen variable");
   params.addParam<bool>("fv", false, "True to make this variable a finite volume variable");
+  params.addParam<bool>(
+      "array",
+      false,
+      "True to make this variable a array variable regardless of number of components");
   params.addParamNamesToGroup("scaling eigen", "Advanced");
 
   params.addParam<bool>("use_dual", false, "True to use dual basis for Lagrange multipliers");
@@ -107,8 +111,10 @@ MooseVariableBase::MooseVariableBase(const InputParameters & parameters)
     paramError("family", "finite volume (fv=true) variables must be have MONOMIAL family");
   if (getParam<bool>("fv") && _fe_type.order != 0)
     paramError("order", "finite volume (fv=true) variables currently support CONST order only");
-
+  bool is_array = getParam<bool>("array");
   if (_count > 1)
+    mooseAssert(is_array, "Must be true with component > 1");
+  if (is_array)
   {
     auto name0 = _sys.system().variable(_var_num).name();
     std::size_t found = name0.find_last_of("_");
@@ -117,7 +123,10 @@ MooseVariableBase::MooseVariableBase(const InputParameters & parameters)
     _var_name = name0.substr(0, found);
   }
   else
+  {
+    mooseAssert(_count == 1, "component size of normal variable (_count) must be one");
     _var_name = _sys.system().variable(_var_num).name();
+  }
 }
 
 const std::vector<dof_id_type> &

test/tests/variables/array_variable/array_variable_size_one_test.i

@@ -0,0 +1,67 @@
+[Mesh]
+  [square]
+    type = GeneratedMeshGenerator
+    nx = 3
+    ny = 3
+    dim = 2
+  []
+[]
+
+[Variables]
+  [u]
+    order = CONSTANT
+    family = MONOMIAL
+    components = 1
+    array = true
+  []
+[]
+
+[Kernels]
+  [diff]
+    type = ArrayDiffusion
+    variable = u
+    diffusion_coefficient = dc
+  []
+  [reaction]
+    type = ArrayReaction
+    variable = u
+    reaction_coefficient = rc
+  []
+  [source]
+    type = ArrayBodyForce
+    variable = u
+    function = '1'
+  []
+[]
+
+[BCs]
+  [all]
+    type = ArrayVacuumBC
+    boundary = 'left right top bottom'
+    variable = u
+  []
+[]
+
+[Materials]
+  [dc]
+    type = GenericConstantArray
+    prop_name = dc
+    prop_value = '1'
+  []
+  [rc]
+    type = GenericConstantArray
+    prop_name = rc
+    prop_value = '2'
+  []
+[]
+
+[Executioner]
+  type = Steady
+  solve_type = 'NEWTON'
+[]
+
+[Outputs]
+  [out]
+    type = Exodus
+  []
+[]

test/tests/variables/array_variable/tests

@@ -7,4 +7,21 @@
     issues = '#6881'
     design = 'ArrayMooseVariable.md'
   [../]
+  [array_variable_size_one]
+    type = 'Exodiff'
+    input = 'array_variable_size_one_test.i'
+    exodiff = 'array_variable_size_one_test_out.e'
+    requirement = 'MOOSE shall be able to define an array variable with component size one.'
+    issues = '#19564'
+    design = 'ArrayMooseVariable.md'
+  []
+  [array_variable_array_false]
+    type = 'RunException'
+    input = 'array_variable_size_one_test.i'
+    cli_args = 'Variables/u/components=2 Variables/u/array=false'
+    requirement = 'MOOSE shall report a reasonable error when defining a variable with multiple components not as an array variable.'
+    issues = '#19564'
+    expect_err = "'array' is set to false."
+    design = 'ArrayMooseVariable.md'
+  []
 []