refactor: limit magic paths use

[kdrienCG]

This PR reduces the use of magic paths to access common objects for developers ("/Problem/domain/", "/Problem/domain/Constitutive", "/Problem/Events/", etc)

It introduces a GlobalViewKeys struct to provide a centralized definition of the names of these common objects.

It also adds a ProblemManagerBase lightweight interface over the ProblemManager that gives typed access to these objects without requiring to bring the full ProblemManager

---

Example of its use:

Group & problemManager = this->getGroupByPath( "/Problem" );
Group & physicsSolverManager = problemManager.getGroup( "Solvers" );

is replaced by:

PhysicsSolverManager & physicsSolverManager = getProblemManagerBase( *this ).getPhysicsSolverManager();

[MelReyCG]

Suggested change

	struct GlobalViewKeys
	struct ProblemViewKeys

[MelReyCG]

Suggested change

	static constexpr char const * problem() { return "Problem"; }
	static constexpr char const * problemManager() { return "Problem"; }

[MelReyCG]

Suggested change

	/**
	* @struct GlobalViewKeys
	*/
	/**
	* @brief All root data-repository view-keys of a given GEOS problem.
	*/

[MelReyCG]

I would like to propose a new version to go all the way with this approach:

Suggested change

	/**
	* @file ProblemManagerBase.hpp
	*/
	#ifndef GEOS_DATAREPOSITORY_PROBLEMMANAGERBASE_HPP_
	#define GEOS_DATAREPOSITORY_PROBLEMMANAGERBASE_HPP_
	#include "dataRepository/Group.hpp"
	namespace geos
	{
	class DomainPartition;
	class EventManager;
	class ExternalDataSourceManager;
	class FieldSpecificationManager;
	class FunctionManager;
	class GeometricObjectManager;
	class MeshManager;
	class NumericalMethodsManager;
	class OutputManager;
	class PhysicsSolverManager;
	class TasksManager;
	namespace constitutive
	{
	class ConstitutiveManager;
	}
	namespace dataRepository
	{
	/**
	* @class ProblemManagerBase
	*/
	class ProblemManagerBase : public Group
	{
	public:
	using Group::Group;
	virtual DomainPartition & getDomainPartition() = 0;
	virtual DomainPartition const & getDomainPartition() const = 0;
	virtual constitutive::ConstitutiveManager & getConstitutiveManager() = 0;
	virtual constitutive::ConstitutiveManager const & getConstitutiveManager() const = 0;
	virtual EventManager & getEventManager() = 0;
	virtual EventManager const & getEventManager() const = 0;
	virtual ExternalDataSourceManager & getExternalDataSourceManager() = 0;
	virtual ExternalDataSourceManager const & getExternalDataSourceManager() const = 0;
	virtual FieldSpecificationManager & getFieldSpecificationManager() = 0;
	virtual FieldSpecificationManager const & getFieldSpecificationManager() const = 0;
	virtual FunctionManager & getFunctionManager() = 0;
	virtual FunctionManager const & getFunctionManager() const = 0;
	virtual GeometricObjectManager & getGeometricObjectManager() = 0;
	virtual GeometricObjectManager const & getGeometricObjectManager() const = 0;
	virtual MeshManager & getMeshManager() = 0;
	virtual MeshManager const & getMeshManager() const = 0;
	virtual NumericalMethodsManager & getNumericalMethodsManager() = 0;
	virtual NumericalMethodsManager const & getNumericalMethodsManager() const = 0;
	virtual OutputManager & getOutputManager() = 0;
	virtual OutputManager const & getOutputManager() const = 0;
	virtual PhysicsSolverManager & getPhysicsSolverManager() = 0;
	virtual PhysicsSolverManager const & getPhysicsSolverManager() const = 0;
	virtual TasksManager & getTasksManager() = 0;
	virtual TasksManager const & getTasksManager() const = 0;
	virtual string const & getProblemName() const = 0;
	virtual string const & getInputFileName() const = 0;
	virtual string const & getRestartFileName() const = 0;
	virtual string const & getSchemaFileName() const = 0;
	};
	/**
	* @brief Gives the ProblemManagerBase from the given Group
	* @param group The current Group in the Problem tree
	* @return A reference to the ProblemManagerBase
	*/
	inline ProblemManagerBase & getProblemManagerBase( Group & group )
	{
	Group * current = &group;
	while( current->hasParent() )
	{
	current = &current->getParent();
	}
	ProblemManagerBase * const root = dynamic_cast< ProblemManagerBase * >( current );
	return *root;
	}
	/**
	* @copydoc getProblemManagerBase( Group & )
	*/
	inline ProblemManagerBase const & getProblemManagerBase( Group const & group )
	{
	Group const * current = &group;
	while( current->hasParent() )
	{
	current = &current->getParent();
	}
	ProblemManagerBase const * const root = dynamic_cast< ProblemManagerBase const * >( current );
	return *root;
	}
	} /* namespace dataRepository */
	} /* namespace geos */
	#endif /* GEOS_DATAREPOSITORY_PROBLEMMANAGERBASE_HPP_ */
	/**
	* @file IProblemRepository.hpp
	*/
	#ifndef GEOS_DATAREPOSITORY_IPROBLEMREPOSITORY_HPP_
	#define GEOS_DATAREPOSITORY_IPROBLEMREPOSITORY_HPP_
	#include "dataRepository/Group.hpp"
	namespace geos
	{
	namespace dataRepository
	{
	/**
	* @brief Gives the problem data repository interface from the given Group
	* @param group The current Group in the Problem tree
	* @return A reference to the problem data repository interface
	*/
	inline IProblemRepository & getProblemRepository( Group & group )
	/**
	* @copydoc getIProblemRepository( Group & )
	*/
	inline IProblemRepository const & getProblemRepository( Group const & group )
	/**
	* @brief Interface for an object which contain all the problem data-repository
	*/
	class IProblemRepository
	{
	public:
	/**
	* @brief Get a root data-repository object (a manager) of a given problem.
	* - The consumer need to include the type definition
	* - The interface implementation needs to implement a specialization for each types manager.
	* @tparam ManagerType the type of the root data-repository object we want to get (DomainPartition, EventManager...)
	* @return ManagerType& the root data-repository object instance reference
	*/
	template< typename ManagerType >
	virtual ManagerType & getRootObject() = 0;
	/**
	* @brief Get a root data-repository object (a manager) of a given problem.
	* - The consumer need to include the type definition
	* - The interface implementation needs to implement a specialization for each types manager.
	* @tparam ManagerType the type of the root data-repository object we want to get (DomainPartition, EventManager...)
	* @return ManagerType const & the root data-repository object instance reference
	*/
	template< typename ManagerType >
	virtual ManagerType const & getRootObject() const = 0;
	// if an abstract Group getting method is absolutely needed, we can add:
	//
	// virtual Group & getManager( string_view managerKey ) = 0;
	// virtual Group const & getManager( string_view managerKey ) const = 0;
	//
	// ... but ideally, we don't want to propose these to remove any "invisible" circular dependency practice.
	};
	/**
	* @name Inline functions implementation
	*/
	///@{
	inline IProblemRepository & getManagerRegistry( Group & group )
	{
	Group * current = &group;
	while( current->hasParent() )
	{
	current = &current->getParent();
	}
	IProblemRepository * const root = dynamic_cast< IProblemRepository * >( current );
	return *root;
	}
	inline IProblemRepository const & getIProblemRepository( Group const & group )
	{
	Group const * current = &group;
	while( current->hasParent() )
	{
	current = &current->getParent();
	}
	IProblemRepository const * const root = dynamic_cast< IProblemRepository const * >( current );
	return *root;
	}
	///@}
	} /* namespace dataRepository */
	} /* namespace geos */
	#endif /* GEOS_DATAREPOSITORY_IPROBLEMREPOSITORY_HPP_ */

I push your almost-interface type approach a bit further, and I see the following benefits:

• Each interface consumer need the declaration of the needed type,
• Only need to add template specialisation for each possible getRootObject() type in ProblemManager.cpp,
• No need to manipulate ProblemManager view-keys, only the type of the manager is needed (excepted for implementation, which I think is ideal),
• We discourage a lot to create invisible circular dependancy
  • no need for forward declaration, explicit type will be used by consumer,
  • no abstract Group obtained by a name,
  • no assumption on the data-hierarchy structure.
• We lock the mutability of the root-Group (unable to add sub-Groups to ProblemManager without being explicit with its type).

Last remarks:

• If that does not compile (linkage) or if we don't want virtual method implemented in the ProblemManager package, we can implement that in a ProblemRepositoryImpl class (with its own cpp) and keep the interface approach (no Group inheritance/exposure).
• I would let the commented versions to consolidate and explain the approach.