modules: use projections format for naming schemes (#16629)

* update tcl naming_scheme to use projections

* add projections to lmod modules

lib/spack/docs/build_systems/intelpackage.rst

@@ -1055,6 +1055,6 @@ Footnotes
    2. Set the hash length in ``install-path-scheme``, also in ``config.yaml``
       (:ref:`q.v. <config-yaml>`).
    3. You will want to set the *same* hash length for
-      :ref:`tcl module files <modules-naming-scheme>`
-      if you have Spack produce them for you, under ``naming_scheme`` in
-      ``modules.yaml``.  Other module dialects cannot be altered in this manner.
+      :ref:`module files <modules-projections>`
+      if you have Spack produce them for you, under ``projections`` in
+      ``modules.yaml``.

lib/spack/docs/module_file_support.rst

@@ -459,14 +459,14 @@ is compiled with ``gcc@4.4.7``, with the only exception of any ``gcc``
 or any ``llvm`` installation.
 
 
-.. _modules-naming-scheme:
+.. _modules-projections:
 
-"""""""""""""""""""""""""""
-Customize the naming scheme
-"""""""""""""""""""""""""""
+"""""""""""""""""""""""""""""""
+Customize the naming of modules
+"""""""""""""""""""""""""""""""
 
 The names of environment modules generated by spack are not always easy to
-fully comprehend due to the long hash in the name. There are two module
+fully comprehend due to the long hash in the name. There are three module
 configuration options to help with that. The first is a global setting to
 adjust the hash length. It can be set anywhere from 0 to 32 and has a default
 length of 7. This is the representation of the hash in the module file name and
@@ -500,20 +500,46 @@ version of python a set of python extensions is associated with. Likewise, the
 ``openblas`` string is attached to any program that has openblas in the spec,
 most likely via the ``+blas`` variant specification.
 
+The most heavyweight solution to module naming is to change the entire
+naming convention for module files. This uses the projections format
+covered in :ref:`adding_projections_to_views`.
+
+.. code-block:: yaml
+
+  modules:
+    tcl:
+      projections:
+        all: '{name}/{version}-{compiler.name}-{compiler.version}-module'
+        ^mpi: '{name}/{version}-{^mpi.name}-{^mpi.version}-{compiler.name}-{compiler.version}-module'
+
+will create module files that are nested in directories by package
+name, contain the version and compiler name and version, and have the
+word ``module`` before the hash for all specs that do not depend on
+mpi, and will have the same information plus the MPI implementation
+name and version for all packages that depend on mpi.
+
+When specifying module names by projection for Lmod modules, we
+recommend NOT including names of dependencies (e.g., MPI, compilers)
+that are already in the LMod hierarchy.
+
+
+
 .. note::
-   TCL module files
-     A modification that is specific to ``tcl`` module files is the possibility
-     to change the naming scheme of modules.
+   TCL modules
+     TCL modules also allow for explicit conflicts between modulefiles.
 
      .. code-block:: yaml
 
-       modules:
-         tcl:
-           naming_scheme: '{name}/{version}-{compiler.name}-{compiler.version}'
-           all:
-             conflict:
-               - '{name}'
-               - 'intel/14.0.1'
+        modules:
+          enable:
+            - tcl
+          tcl:
+            projections:
+              all: '{name}/{version}-{compiler.name}-{compiler.version}'
+            all:
+              conflict:
+                - '{name}'
+                - 'intel/14.0.1'
 
      will create module files that will conflict with ``intel/14.0.1`` and with the
      base directory of the same module, effectively preventing the possibility to