[racket] Dynamic module loading

Hello. I've been trying to get a particular use case for module loading to
work, and, while I have a mostly functional solution, I am unsure whether I
am using the best infrastructure for the task. The explanation is a bit
involved, but the basic question is what is the right way to update a
running system using values generated by racket code (update as in feed new
data to, not reload the module bindings of).

I have a text-based game client that needs to be able to dynamically load
user-defined aliases while running. Ordinarily this could be solved by
simply reading a file of alias definitions and updating the structure in
memory. However, as the alias system may potentially be quite complex, I
was hoping to use both the racket language and module system to define
these aliases. Ie, I might have inventory-aliases.rkt, which requires
item-aliases.rkt in order to reuse helper code defined in the latter in the
former.

My current solution involves having all alias code as well as the main
program require a common base.rkt that provides a single aliases #hash.
Each alias file, when loaded, destructively sets all its aliases into the
hash, which are in turn usable by the main program.

When a user updates an alias file, I dynamic-rerequire the file, which,
since the hash set!s are idempotent, mostly works. The trouble is that if a
user deletes an alias, I do not know to get rid of it in my hash structure.
Moreover, I cannot throw out the hash because dynamic-rerequire only reruns
changed modules.

Before I continue on down this rabbit hole and start adjusting timestamps
to have dynamic-rerequire do what I need it to do, I wanted to ask whether
there was a more canonical way to achieve my ends. I get the impression
that I am somewhat hijacking the module system since I am mostly using it
to structure the alias code, but then am trying to extract something that
is not quite an exported set of values from it. Would it make sense perhaps
to construct an evaluator out of the alias definitions and evaluate user
inputs in that language? I am not intimately familiar with the module
system, and so am doing a bit of a random walk around its infrastructure as
I learn more about it.

I sense this question may be a bit obscure, so thank you in advance to
anyone who has any insights to share on the matter.

Evan
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