[Lmod-users] Hooking lmod methods

[<mal...@ci...>]

Hey, I hope this finds you well,

I'm trying to hook prepend_path & append_path so that if a given environment variable is used, I also append it into another variable.

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prepend_path( "LD_LIBRARY_PATH","/opt/apps/ddt/5.0.1/lib") becomes:
prepend_path( "LD_LIBRARY_PATH","/opt/apps/ddt/5.0.1/lib")
prepend_path( "MY_OTHER_VARIABLE","/opt/apps/ddt/5.0.1/lib")
--------

The code doing this hooking like like that:

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local function Main(context)
    local function HookPathMethods(function_name, source, target)
        local original_alter_path = context[function_name]
        local alter_path = function(...)
            local parameters = {...}
            if parameters[1] == source then
                parameters[1] = target
                original_alter_path(table.unpack(parameters))
            end
            return original_alter_path(...)
        end
        context[function_name] = alter_path
    end
    HookPathMethods("prepend_path", "LD_LIBRARY_PATH", "MY_LD_LIBRARY_PATH")
    HookPathMethods("append_path", "LD_LIBRARY_PATH", "MY_LD_LIBRARY_PATH")
end
return { Main = Main }
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Now, I currently have this code,  which is injected through:
--------
assert(loadfile("/path/to/hook.lua"))().Main(_ENV)
--------

This does not work when purging modules, the effect of the hooked prepend_path path remains. I then tried using the sitePackage.lua, like so:

--------
local function HookPathMethods(function_name, source, target)
    local original_function = _ENV[function_name]
    return function(...)
        local parameters = {...}
        if parameters[1] == source then
            parameters[1] = target
            original_function(table.unpack(parameters))
        end
        return original_function(...)
    end
end
sandbox_registration{
    prepend_path = HookPathMethods("prepend_path", "LD_LIBRARY_PATH", "MY_LD_LIBRARY_PATH"),
    append_path = HookPathMethods("append_path", "LD_LIBRARY_PATH", "MY_LD_LIBRARY_PATH")
}
--------

This works like a charm (so it seems), but it is easy fora user to usnet the LMOD site package env variable and so its brittle. I think I'm goingto stay with SitePackage, but is there a wait to make the solution above work ? Or an alternative way of doing this whole "shenanigans".
I'm very much looking for advice or more conventional ways of doing that. The fact is that we have a lot of common things between our modules and wish to factorize.

Have a nice day, regards,
-- 
Etienne Malaboeuf 
Ingénieur de recherche HPC, Département Calcul Intensif (DCI) 

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