Deprecate MeshModifiers and remove tests - push on the apps to do the same.

[permcody]

Reason

MeshModifiers and MeshGenerators have the same capabilities. We need to deprecate the old system (Modifiers) so that we don't have to maintain to separate systems moving forward. This is important since we are working on documentation and requirements and I don't want to duplicate that effort.

Design

Completely replace the capabilities of MeshModifiers with MeshGenerators.

Impact

Moderate - Moderators are used throughout the "herd" so several applications will be impacted as we move away from the old system.

[gambka]

I am working on removing all usage of MeshModifiers in Bison. However, all of the MeshGenerator capabilities require the input of another mesh generator used to create the mesh to modify. This is fine in almost all cases. However, a few months ago we discussed a specific use case where in an Action we check that the mesh is of a certain type as the action is only valid for that particular type of mesh. I had changed the action to check for the mesh generator version of that mesh type at one point, which worked fine until you tried to restart. As far as I recall Mesh objects are called on restart/recover but mesh generators are not and therefore we abandoned the MeshGenerator version.

Unfortunately, we have a test that uses that mesh type with a mesh modifier and now with the deprecation of mesh modifiers we cannot fix the deprecation of the test since we do not have the MeshGenerator version of the mesh type. Moreover, since we have a recover testing target, the test would fail the check in the action if we did use a MeshGenerator version to create the mesh.

What should be done in this case since mesh generators operate on other mesh generators and not on the mesh like mesh modifiers do?

[permcody]

@gambka - You are absolutely right. That Mesh "meta-data" system needs to be designed and built before we fully deprecate the MeshModifiers. For now - I wouldn't take any action. I'm willing to be less aggressive on the deprecation date as I don't know for sure whether we'll get this done before the BISON assessment. I guess we'll just have to prepare for the case where we have undocumented-deprecated objects in the system...

[gambka]

I will still put a PR into Bison that removes the deprecated objects from the other 17 of the 22 tests failing the --error-deprecated target. The other 5 use the Mesh "meta-data".

[permcody]

Well the other reason I don't want you to jump the gun here is that we are actively talking about rearranging the MeshGenerators syntax (nesting it underneath the [Mesh] block). If you fixup all your tests right now, we may have to fix them up again if we move that syntax. Hopefully we'll make that decision quickly!

[gambka]

Well I have the branch ready and was just about to submit a PR. I'll keep the branch with the changes until a decision is made and then update the commit. Moving the syntax will affect a lot more tests because we have some using MeshGenerators for creating the mesh but no modifiers that will have to changed as well.

I should probably also hold off until #13833 gets merged as well as that change will need to be incorporated.

[veeshy]

Just wanted to mention #13473 here since it’s a feature I use regularly and would be removed in this deprecation