Differences between versions 3.2 and 4
**************************************

This document lists functionality differences between Modules version
3.2 and Modules version 4. Modules version 3.2 is also referred in
this document as *compatibility version* whereas Modules version 4 is
also referred as *new main version*. Modules version 4 is based on
what was previously called Modules-Tcl. The goal of this document is
to reference the features of the compatibility version that are
missing or behave differently on the new main version and the features
that can only be found on this new version.

First part the of the document covers the features that are missing or
that behave differently on Modules 4 than on compatibility version.
The second part of the document covers the features that are specific
to the Modules 4 version thus missing on compatibility version.
Comparison takes as a basis version "3.2.10" of compatibility version
against Modules version "4.0". Any change made past these versions
will explicitly mention the release number starting from the
difference appears or disappears.

Regarding missing features, this document only lists their name or the
command line argument related to them. Please refer to the module and
the modulefile man pages of the compatibility or main version to learn
the details about these features.

Last but not least, the numerous bugs or limitations spotted on
Modules "3.2" across the years have been fixed in Modules "4.0". The
list of reported issues that have been solved are available on the
project code forge.


Features missing or with different behavior than compatibility version
======================================================================

This section describes the features of the compatibility version that
are not supported or that behave differently on Modules 4.


Package Initialization
----------------------

"MODULESBEGINENV" environment snapshot functionality is not supported
on version 4. Modules collection mechanism should be preferred to save
and restore sets of enabled modulepaths and loaded modulefiles.
Modules 4 also introduces a system configuration file *init/modulerc*,
located in Modules installation directory. Starting version "4.3",
this file could also be *etc/initrc*. This *modulerc*/*initrc* file is
sourced by Modules shell initialization scripts and helps to setup the
initial environment right after initializing the **module** command.


Command line switches
---------------------

**--human**

**--create**, **-c**

**--userlvl** lvl, **-u** lvl

   These command line switches are not supported on Modules 4. When
   these options are passed on the command-line, it produces an
   *Unsupported option* warning and command is ran with the
   unsupported switches ignored.

**--ter**

**--lon**

**--sil**

**--verb**

   These intermediate-form command line switches are not supported on
   Modules 4. Short or long switch name should be used instead.

"-h"

   This command line switch is short version of "--help" switch on
   Modules 4 whereas it is short version of **--human** switch on
   compatibility version.

"--force", "-f"

   This command line switch was not supported starting Modules version
   "4.0" but reintroduced starting version "4.2" with a different
   meaning: instead of enabling an active dependency resolution
   mechanism "--force" command line switch now enables to by-pass
   dependency consistency when loading or unloading a *modulefile*.

"--verbose", "-v"

"--silent", "-s"

   These command line switches were not supported starting Modules
   version "4.0" but reintroduced starting version "4.3". However,
   reintroduced "--silent" switch does not redirect stderr channel to
   "/dev/null" if stderr is found not to be a tty.

"--icase", "-i"

   This command line switch was not supported starting Modules version
   "4.0" but reintroduced starting version "4.4". When "--icase"
   switch is now set it applies to search query string and module
   specificiation on all sub-commands and modulefile Tcl commands.


Module Sub-Commands
-------------------

On compatibility version, paths composing the "MODULEPATH" environment
variable may contain reference to environment variable. These variable
references are resolved dynamically when "MODULEPATH" is looked at
during module sub-command action like "avail". This feature was
missing on Modules "4.0" but it has been re-introduced on Modules
"4.1".

"update"

   This module sub-commands is not supported on Modules 4.

"clear"

   This command line switch was not supported starting Modules version
   "4.0" but reintroduced starting version "4.3". It now takes into
   account the "--force" command-line switch to skip confirmation
   dialog.

"refresh"

   On compatibility version, only the shell aliases defined by the
   currently loaded modulefiles are set again on a "refresh" command.
   Whereas on new main version this command is an alias on the
   "reload" command that "unload" then "load" all the currently loaded
   modulefiles.

"help"

   Compatibility version redirects output made on stdout in
   "ModulesHelp" Tcl procedure to stderr.

   During an "help" sub-command, only the "ModulesHelp" Tcl procedure
   of a modulefile is interpreted on compatibility version. Version 4
   interprets all the content of the modulefile, then call the
   "ModulesHelp" procedure if it exists.

   On version 4, "ModulesHelp" subroutine is not ran if an error
   occurred during the interpretation of the *modulefile* main body.

"display"

   On version 4, "ModulesDisplay" subroutine is not ran if an error
   occurred during the interpretation of the *modulefile* main body.

"avail"

   On compatibility version, the same Tcl interpreter is used for the
   interpretation of all *.modulerc* or *.version* files during an
   "avail" command but the state of this interpreter is not reset
   between each interpretation. So some variable and procedure
   definitions may spread from one interpretation to another on this
   compatibility version. Modules 4 reuses the same interpreter for
   all *.modulerc* or *.version* interpretation but it is cleaned
   between each interpretation to protect from definition spread.

   In case of "--terse" or "--long" mode, all enabled modulepaths will
   be displayed whether they hold result to display or not. Modules 4
   outputs only the modulepaths where matching results are found.
   Modulepaths with no result to report are discarded from output.

"apropos"

   On Modules 4, *string* passed as argument is always searched in a
   case insensitive manner.

"load"

   On Modules 4, the value of an environment variable is set even if
   the new value is the same as the current value of this variable in
   environment.

   When an already loaded *modulefiles* is asked for load again,
   compatibility version will refresh the shell alias definition this
   modulefile hold if any, whereas Modules 4 will ignore the new load
   order.

   In case of *modulefile* loading another modulefile, if sub-
   modulefile load fails calling modulefile will still be loaded on
   compatibility version whereas Modules 4 will also abort calling
   modulefile load.

   Starting with version "4.1", content sent to the "stdout" channel
   during a *modulefile* interpretation is spooled to effectively
   transmit this content to stdout after rendering the environment
   changes made by this modulefile.

"unload"

   On Modules 4, the value of an environment variable is set even if
   the new value is the same as the current value of this variable in
   environment.

   Compatibility version enables to load a *modulefile* by passing on
   the command-line the name of a module alias or symbolic version
   pointing to this modulefile. However this module alias or symbolic
   version name cannot be used to unload the modulefile once loaded.
   Modules 4 enables to pass a module alias or symbolic version name
   to unload a loaded modulefile referred by this name.

   On versions "4.0" and "4.1", unloading an unexistent modulefile
   generates an *Unable to locate modulefile* error. Starting with
   version "4.2", unloading a module only looks at loaded module list
   and does not trigger a modulefile search. So starting version "4.2"
   the same behavior than Modules compatibility version is obtained.

   Starting with version "4.1", content sent to the "stdout" channel
   during a *modulefile* interpretation is spooled to effectively
   transmit this content to stdout after rendering the environment
   changes made by this modulefile.

   When the specified module to unload matches multiple loaded
   modules, Modules 4 unloads lastly loaded module whereas
   compatibility version unloads firstly loaded module. A
   configuration option "unload_match_order" has been introduced in
   version "4.3" and it enables to restore the behavior of
   compatibility version when it is set to "returnfirst".

"switch"

   When switching on version 4 an *old* modulefile by a *new* one, no
   error is raised if *old* modulefile is not currently loaded. In
   this situation compatibility version throws an error and abort
   switch action.

   When switching on Modules 4 an *old* modulefile by a *new* one,
   this *new* modulefile does not keep the position that the *old*
   modulefile had in the "LOADEDMODULES" list as done on compatibility
   version but it is appended to the end of the list. Same goes for
   PATH-like environment variables: replaced PATH component is
   appended to the end or prepended to the beginning of the relative
   PATH-like variable, not appended or prepended relatively to the
   position hold by the swapped PATH component.

   When a modulefile loads another modulefile with a *module load*
   order, this sub-module is not unloaded when the top modulefile is
   swapped-out during a "switch" command on compatibility version.
   Version 4 interprets the swapped-out modulefile in unload mode, so
   the *module load* order is interpreted as *module unload* order and
   sub-module is unloaded.

"use"

   When the modulepath to enable is passed as a relative path,
   compatibility version will set it using passed relative name
   whereas Modules 4 will determine the corresponding absolute path
   and will register it rather passed relative name.

"unuse"

   Modules 4 provides path element counting feature which increases a
   reference counter each time a given path entry is added to a given
   environment variable. This feature also applies to the "MODULEPATH"
   environment variable. As consequence a modulepath entry element is
   removed from the modulepath enabled list only if the related
   element counter is equal to 1. When unusing a modulepath if its
   reference counter is greater than 1, modulepath is kept enabled and
   reference counter is decreased by 1.

"whatis"

   On Modules 4, environment variable edition commands (*setenv*,
   *unsetenv*, *append-path*, *prepend-path* and *remove-path*) do no
   set variable to the defined value on the modulefile evaluation
   context during a "whatis" evaluation. Instead environment variables
   are initialized with an empty value if undefined, to avoid raising
   error when attempting access to an undefined element during the
   modulefile evaluation.

"initadd"

"initprepend"

"initswitch"

   On version 4 no message is displayed to give details on how list of
   modulefiles to load has been altered in initialization file.

"initrm"

   No message is displayed on Modules 4 to inform of the modulefiles
   that have been removed from the loading list in initialization
   file.

   Empty "module load" line is left on version 4 when last modulefile
   from a line is asked to be removed. On compatibility version
   "module load null" line is set in this case.

"initclear"

   Empty "module load" lines are left on version 4 whereas "module
   load null" lines are set on compatibility version.


Modules Specific Tcl Commands
-----------------------------

On version 4 the characters that have a special meaning when rendered
in shells are escaped when used in value to set environment variables,
shell alias or shell functions. Thus it is possible to set environment
elements with value containing these special characters (like
backticks). On version 3 these special characters were evaluated by
shell when recording the environment changes implied by modulefile
evaluation.

"append-path"

"prepend-path"

   Modules 4 produces an error when adding a bare colon character *:*
   as a path element to a path-like variable, as this colon cannot be
   distinguished from the colon used for path separator.

   Modules 4 supports adding or removing empty path element to a path-
   like variable, whereas compatibility version looses track of this
   path element when the path-like variable is modified afterward.
   Empty path element enables to set a leading colon character *:*,
   which has a specific meaning on some regular environment variable
   like "MANPATH" or "LD_LIBRARY_PATH".

   When adding a path element to the "MANPATH" environment variable,
   Modules 4 is treating this variable like any other whereas a
   special treatment was applied on compatibility version: a default
   MANPATH value, set at configure time, was appended in case
   "MANPATH" variable was unset.

"remove-path"

   Modules 4 provides path element counting feature which increases a
   reference counter each time a given path entry is added to a given
   environment variable. As consequence a path entry element is
   removed from a path-like variable only if the related element
   counter is equal to 1. If this counter is greater than 1, path
   element is kept in variable and reference counter is decreased by
   1.

   When unloading a modulefile, "remove-path" command is not applied
   to environment variable on Modules 4, whereas on compatibility
   version it is processed the exact same way than when loading
   modulefile.

"exit"

   On Modules 4 code passed to the "exit" Modules specific Tcl command
   will not be thrown to be the **module** return value.

"module-alias"

"module-version"

   In case the specified aliased module or the symbolic version
   introduces a resolution loop with already defined aliases or
   symbolic versions, this new alias or symbolic version is not
   registered and an error message is raised. On compatibility
   version, alias or symbolic version introducing loop are registered
   as the modulefile resolution is not computed at registration time.

"module-info"

   **module-info flags**

   **module-info trace**

   **module-info tracepat**

   **module-info user**

      These "module-info" options are related to compatibility
      version-specific features so they are available on Modules 4 but
      with a dummy implementation that always returns false or an
      empty value.

   **module-info mode**

      During an "unload" sub-command, "unload" is returned instead of
      "remove". However if *mode* is tested against "remove" value,
      true will be returned.

      During a "switch" sub-command, "unload" then "load" is returned
      instead of "switch1" then "switch2" then "switch3". However if
      *mode* is tested against "switch" value, true will be returned.

   **module-info name**

      If the module name passed to the command-line has been specified
      as a full path name, the **module-info name** used in modulefile
      returns this file base name on compatibility version whereas it
      returns on Modules 4+ the full path name as it is identified by
      this name once loaded.

   **module-info version**

      Declared aliases or symbolic versions are not registered anymore
      if they introduce a resolution loop. As a result **module-info
      version** does not return an "*undef*" string value as it does
      not face resolution loop situation anymore.

   **module-info symbols**

      Declared aliases or symbolic versions are not registered anymore
      if they introduce a resolution loop. As a consequence symbolic
      versions introducing loop situation are not part anymore of the
      **module-info symbols** returned result as they are not
      registered.

      A symbolic version sets on a module alias will be propagated
      toward the resolution path to also apply to the relative
      *modulefile* if it still correspond to the same module name.

"module-log"

"module-trace"

"module-user"

"module-verbosity"

   These Modules specific Tcl commands are related to compatibility
   version-specific features so they are available on Modules 4 but
   with a dummy implementation that always displays a warning message
   saying the command is not implemented.

"module-whatis"

   When multiple words are passed as argument to "module-whatis" but
   they are not enclosed in double-quotes or curly braces they will be
   displayed as a single line on Modules 4 whereas compatibility
   version displays them as one line per word.

"set-alias"

   Whereas compatibility version sets a shell function when variables
   are in use in alias value on Bourne shell derivatives, Modules 4
   always defines a shell alias never a shell function.


Locating Modulefiles
--------------------

On version 4, when a module alias is set and overrides name of an
existing directory, this alias is taken into account to locate the
default version of this module name and the *modulefiles* locating in
the directory are ignored.

When looking for an implicit default in a *modulefile* directory,
aliases are taken into account in addition to *modulefiles* and
directories to determine the highest numerically sorted element.

Modules 4 will resolve module alias or symbolic version passed to
"unload" command to then remove the loaded modulefile pointed by the
mentioned alias or symbolic version.

Modules 4 resolves module alias or symbolic version pointing to a
*modulefile* located in another modulepath.

When locating *modulefiles* on Modules 4, if a *.modulerc*, a
*.version*, a directory or a *modulefile* cannot be read during the
search it is simply ignored with no error message produced. Visibility
of *modulefiles* can thus be adapted to the rights the user has been
granted. Exception is made when trying to directly access a directory
or a *modulefile*. In this case, the access issue is returned as an
error message. Access issue is also returned when a direct access is
made to a module alias or a symbolic version targeting an unreadable
*modulefile*.


Features specific to the new main version
=========================================

This section describes the features of Modules version 4 that are not
supported on the compatibility version. Please refer to the above
section for features supported by both versions but behaving
differently.


Package Initialization
----------------------

Compatibility version does not support *fish*, *lisp*, *tcl* and *R*
as code output.

On version 4 and for *sh*, *bash*, *ksh*, *zsh* and *fish* shells,
text output, like listing from the "avail" command, is redirected from
*stderr* to *stdout* after shell command evaluation if shell is in
interactive mode. Starting version "4.1", this content redirection
occurs if shell session is attached to a terminal.

Starting version "4.5", a new alias or function called **ml** may be
defined at initialization time, to provide a handy frontend to the
**module** command.


Modulecmd startup
-----------------

Starting with version "4.1", "modulecmd.tcl" sources upon invocation a
site-specific configuration script named "siteconfig.tcl". This Tcl
script enables to supersede any global variable or procedure
definition of modulecmd.tcl.


Command line switches
---------------------

The following command line switches appeared on new version of Modules
are not supported on compatibility version.

+--------------+-------------------------------------------------------------------+
| Introduced   | New command line switches                                         |
| in version   |                                                                   |
|==============|===================================================================|
| 4.0          | "--debug", "-D", "--default", "-d", "--latest", "-L"              |
+--------------+-------------------------------------------------------------------+
| 4.1          | "--paginate", "--no-pager"                                        |
+--------------+-------------------------------------------------------------------+
| 4.2          | "--auto", "--no-auto"                                             |
+--------------+-------------------------------------------------------------------+
| 4.3          | "--indepth", "--no-indepth", "--color", "--starts-with", "-S",    |
|              | "-- contains", "-C"                                               |
+--------------+-------------------------------------------------------------------+
| 4.5          | "--json", "-j"                                                    |
+--------------+-------------------------------------------------------------------+
| 4.6          | "--trace", "-T", "--all", "-a", "-DD"                             |
+--------------+-------------------------------------------------------------------+
| 4.7          | "-vv", "--output", "-o", "--width", "-w"                          |
+--------------+-------------------------------------------------------------------+


Module Sub-Commands
-------------------

The following module sub-commands appeared on new version of Modules
are not supported on compatibility version.

+--------------+-------------------------------------------------------------------+
| Introduced   | New module sub-commands                                           |
| in version   |                                                                   |
|==============|===================================================================|
| 4.0          | "reload", "source", "search", "save", "restore", "saverm",        |
|              | "saveshow", "savelist", "path", "paths", "autoinit", "aliases",   |
|              | "test"                                                            |
+--------------+-------------------------------------------------------------------+
| 4.1          | "append-path", "prepend-path", "remove-path", "is-loaded", "is-   |
|              | saved" "is-used", "is-avail", "info-loaded"                       |
+--------------+-------------------------------------------------------------------+
| 4.3          | "config"                                                          |
+--------------+-------------------------------------------------------------------+
| 4.6          | "sh-to-mod"                                                       |
+--------------+-------------------------------------------------------------------+

All module sub-commands will return a non-zero exit code in case of
error whereas on compatibility version issues that occurred do not
lead to an exit of the **module** command with a non-zero code.

Starting with version "4.1", **module** function for all scripting
languages, like Perl or Python, always returns a value. In case of
error, a *false* boolean value is returned instead of raising a fatal
exception. For module sub-commands returning a text value, the module
function will actually return this value. In all other cases a *true*
boolean value is returned.

"avail", "whatis" and "apropos"

   Non-critical errors are not displayed on "avail", "whatis" and
   "apropos" sub-commands. Only valid results are returned.

   Module aliases are included in the result of these sub-commands.
   They are displayed in the module path section where they are
   defined or in a *global/user modulerc* section for aliases set in
   user's or global modulerc file. A "@" symbol is added in
   parenthesis next to their name to distinguish them from
   *modulefiles*.

   Search may be performed with an alias or a symbolic version-name
   passed as argument.

   Arguments to these "avail", "whatis" and "apropos" commands may use
   wildcard characters to express glob patterns.


Collections
-----------

Modules collections are not supported on compatibility version.


Environment
-----------

The following environment variables appeared on new version of Modules
are not supported on compatibility version.

+--------------+-------------------------------------------------------------------+
| Introduced   | New environment variables                                         |
| in version   |                                                                   |
|==============|===================================================================|
| 4.0          | "MODULECONTACT", "MODULES_COLLECTION_TARGET",                     |
|              | "MODULES_USE_COMPAT_VERSION", "<VAR>_modshare"                    |
+--------------+-------------------------------------------------------------------+
| 4.1          | "MODULES_CMD", "MODULES_COLLECTION_PIN_VERSION", "MODULES_PAGER", |
|              | "MODULES_RUNENV_<VAR>", "MODULES_RUN_QUARANTINE",                 |
|              | "MODULES_SILENT_SHELL_DEBUG", "<VAR>_modquar"                     |
+--------------+-------------------------------------------------------------------+
| 4.2          | "MODULES_AUTO_HANDLING", "MODULES_LMALTNAME",                     |
|              | "MODULES_LMCONFLICT", "MODULES_LMNOTUASKED", "MODULES_LMPREREQ"   |
+--------------+-------------------------------------------------------------------+
| 4.3          | "MODULES_AVAIL_INDEPTH", "MODULES_COLOR", "MODULES_COLORS",       |
|              | "MODULES_IMPLICIT_DEFAULT", "MODULES_SEARCH_MATCH",               |
|              | "MODULES_SET_SHELL_STARTUP", "MODULES_SITECONFIG",                |
|              | "MODULES_TERM_BACKGROUND", "MODULES_UNLOAD_MATCH_ORDER",          |
|              | "MODULES_VERBOSITY", "MODULES_WA_277"                             |
+--------------+-------------------------------------------------------------------+
| 4.4          | "MODULES_ADVANCED_VERSION_SPEC", "MODULES_EXTENDED_DEFAULT",      |
|              | "MODULES_ICASE"                                                   |
+--------------+-------------------------------------------------------------------+
| 4.5          | "MODULES_ML"                                                      |
+--------------+-------------------------------------------------------------------+
| 4.6          | "MODULES_LMSOURCESH", "MODULES_NEARLY_FORBIDDEN_DAYS"             |
+--------------+-------------------------------------------------------------------+
| 4.7          | "MODULES_SHELLS_WITH_KSH_FPATH", "MODULES_IMPLICIT_REQUIREMENT",  |
|              | "MODULES_LMTAG", "MODULES_TAG_ABBREV", "MODULES_TAG_COLOR_NAME",  |
|              | "MODULES_MCOOKIE_VERSION_CHECK" "MODULES_AVAIL_OUTPUT",           |
|              | "MODULES_AVAIL_TERSE_OUTPUT", "MODULES_LIST_OUTPUT",              |
|              | "MODULES_LIST_TERSE_OUTPUT", "MODULES_TERM_WIDTH"                 |
+--------------+-------------------------------------------------------------------+


Modules Specific Tcl Commands
-----------------------------

The following modulefile Tcl commands appeared on new version of
Modules are not supported on compatibility version.

+--------------+-------------------------------------------------------------------+
| Introduced   | New modulefile Tcl commands                                       |
| in version   |                                                                   |
|==============|===================================================================|
| 4.0          | "module-info command"                                             |
+--------------+-------------------------------------------------------------------+
| 4.1          | "module-info loaded", "is-saved", "is-used", "is-avail", "module- |
|              | virtual"                                                          |
+--------------+-------------------------------------------------------------------+
| 4.2          | "set-function", "unset-function"                                  |
+--------------+-------------------------------------------------------------------+
| 4.6          | "source-sh", "module-hide", "module-forbid", "module-info         |
|              | usergroups", "module-info username"                               |
+--------------+-------------------------------------------------------------------+
| 4.7          | "versioncmp", "module-tag", "module-info tags"                    |
+--------------+-------------------------------------------------------------------+

"conflict" and "prereq"

   Starting with version "4.2", these Modules-specific Tcl commands
   support being called with a symbolic modulefile or a modulefile
   alias passed as argument.

"module"

   In case of "module load" command specifying multiple *modulefiles*,
   when mode is set to "unload" these *modulefiles* will be unloaded
   in the reverse order to ensure correct handling of prerequisites.

   Starting with version "4.7", the "load", "unload" and "switch" sub-
   commands support the "--not-req" option to avoid recording a prereq
   or a conflict requirement toward specified modules.

"append-path" and "prepend-path"

   Starting with version "4.1", both commands handle being called with
   multiple *value* arguments and option "--duplicates" is added.

"remove-path"

   Starting with version "4.1", "remove-path" handles being called
   with multiple *value* arguments and option "--index" is added.

"is-loaded"

   Starting with version "4.1", "is-loaded" supports being called with
   no argument passed. In this case, it returns *true* if any
   modulefile is currently loaded, *false* otherwise.

   Starting with version "4.2", "is-loaded" supports being called with
   a symbolic modulefile or a modulefile alias passed as argument.

   This Modules-specific Tcl command was not enabled for *modulerc*
   evaluation starting Modules version "4.0" but it has been
   reintroduced starting version "4.2.1".


Modules Variables
-----------------

The following Modules-specific Tcl variables appeared on new version
of Modules are not supported on compatibility version.

+--------------+-------------------------------------------------------------------+
| Introduced   | New Modules-specific Tcl variables                                |
| in version   |                                                                   |
|==============|===================================================================|
| 4.7          | "ModuleTool", "ModuleToolVersion"                                 |
+--------------+-------------------------------------------------------------------+
