Consider Spack Manifest Requirements

[CodeGat]

The spack manifest, or spack.yaml, will have necessarily less requirements than the ones imposed on build-cd (the pre/release deployment pipeline to a HPC), as it is meant to be a highly customizable, multi-spec manifest that is used for testing.

However, there may still be constraints that we need to establish to enable concretization/finding of executables that may have similar paths.

[CodeGat]

For example, if we are installing specs under the same environment that have the same name (for example, different installations of mom5 with differing compilers), we need to update both the concretization strategy to at least spack.concretizer.unify:when_possible, and have custom views that get past the following error:

==> Updating view at /opt/environments/mom5-when-possible/.spack-env/view
==> Error: The environment view in /opt/environments/mom5-when-possible/.spack-env/view could not be created, because the following two specs project to the same prefix:
    mom5@=access-om2%intel@=2021.2.0~access-gtracers~deterministic~optimisation_report+restart_repro build_system=makefile type=ACCESS-OM arch=linux-rocky8-x86_64, and
    mom5@=access-om2%intel@=2021.4.0~access-gtracers~deterministic~optimisation_report+restart_repro build_system=makefile type=ACCESS-OM arch=linux-rocky8-x86_64.
    To resolve this issue:
        a. use `concretization:unify:true` to ensure there is only one package per spec in the environment, or
        b. disable views with `view:false`, or
        c. create custom view projections.

The following snippet installs the example correctly:

spack:
  definitions:
    - mom5s:
        - matrix:
          - ['mom5']
          - ['%intel@2021.2.0 target=x86_64', '%intel@2021.4.0 target=x86_64']
  specs:
    - $mom5s
  view:
    default:
      # The root may have to be disambiguated by environment name, or maybe removed? (the default is $SPACK_ROOT/../environments/ENV/.spack-env/view
      root: $SPACK_ROOT/../views
      projections:
        mom5: '{name}/{compiler.name}-{compiler.version}'
  concretizer:
    # Due to different compilers under the same source root
    unify: when_possible