[Modules] Hiding modules

[Xavier D. <xav...@gm...>]

Dear All,

The newly introduced `module-hide` modulefile command enables to
dynamically hide modulefiles, module aliases or symbolic versions specified
to it:

    $ cat /path/to/modulefiles/bar/.modulerc
    #%Module4.6
    module-version bar/1.0 old
    # hide 'old' symbolic version
    module-hide bar/old
    # hide all version 2 and above
    module-hide bar@2:
    $ cat /path/to/modulefiles/.modulerc
    #%Module4.6
    # hide all versions of foo module
    module-hide foo

`module-hide` commands should be placed in module rc files and can leverage
the [Advanced module version specifiers](
https://timeline.noticeable.io/cbzeG7wTvAIqj21zbUmx/posts/advanced-module-version-specifiers)
syntax as shown in the above example.

Hidden modules are excluded from available module search or module
selection unless query refers to hidden module by its exact name:

    $ ml av
    --------------- /path/to/modulefiles ---------------
    bar/1.0  bar/2.0
    $ module load -v foo
    ERROR: Unable to locate a modulefile for 'foo'
    $ module load -v foo/1.0
    Loading foo/1.0
    $ module avail bar/old
    --------------- /path/to/modulefiles ---------------
    bar/1.0(old)

`module-hide` command accepts a `--soft` option to apply a lighter of
hiding to modules:

    $ cat /path/to/modulefiles/qux/.modulerc
    #%Module4.6
    # softly hide all qux modules
    module-hide --soft qux

The soft hiding mode enables to hide modules from full availability listing
yet keeping the ability to select such module for load without having to
use module exact name:

    $ ml av
    --------------- /path/to/modulefiles ---------------
    bar/1.0  bar/2.0
    $ ml av qux
    --------------- /path/to/modulefiles ---------------
    qux/1.0  qux/2.0
    $ module load -v qux
    Loading qux/2.0

Alternatively, a `--hard` option can be set on `module-hide` command to
ensure designated modules do not unveil even if referred by their exact
name:

    $ cat /path/to/modulefiles/qux/.modulerc
    #%Module4.6
    # softly hide all qux modules
    module-hide --soft qux
    # set highest version of qux hard hidden
    module-hide --hard qux/3.0
    $ ml av qux/3.0
    $ ml qux/3.0
    ERROR: Unable to locate a modulefile for 'qux/3.0'

Some users or groups can be set unaffected by hiding mechanism with the
`--not-user` or `--not-group` options:

    $ cat /path/to/modulefiles/quuz/.modulerc
    #%Module4.6
    # hiding does not apply to grp1 and grp2 groups
    module-hide --not-group {grp1 grp2} quuz

    $ id --groups --name
    grp1 grp7
    $ ml av quuz
    --------------- /path/to/modulefiles ---------------
    quuz/1.0  quuz/2.0
    $ ml -v quuz
    Loading quuz/2.0

Hiding mechanism can also be set effective only before or after a given
date time with the `--before` and `--after` options. Accepted date time
format is `YYYY-MM-DD[THH:MM]`.

    $ cat /path/to/modulefiles/fum/.modulerc
    #%Module4.6
    # hide only before a given date
    module-hide --hard --before 2020-09-01T12:00 fum/1.0
    # hide only after a given date
    module-hide --hard --after 2020-09-01 fum/2.0

    $ date
    Fri 04 Sep 2020 06:21:48 AM CEST
    $ ml av fum
    --------------- /path/to/modulefiles ---------------
    fum/1.0

Hidden modules can be included in available module searches if option
`--all`/`-a` is set on `avail`, `aliases`, `whatis` or `search`
sub-commands. Hard hidden modules are unaffected by this option and stay
hidden.

    $ ml av -a
    --------------- /path/to/modulefiles ---------------
    bar/1.0(old)  foo/1.0  fum/1.0   quuz/2.0  qux/2.0
    bar/2.0       foo/2.0  quuz/1.0  qux/1.0

This new feature is available in git repository and will be included in
next release (v4.6).

Regards,
Xavier