new modulefile command to set that module could not be unloaded (sticky)

[xdelaruelle]

The concept of surviving “purge” or “unload” looks rather like such modules being sticky. Such an attribute needs to be flagged in “module list” output, ideally including when “—terse” is active (for parsing). Come to think about it, I’d say such an attribute might be set-able by a declaration, not a code snippet.

Originally posted by @mgsternberg in #267 (comment)

[mgsternberg]

Xavier,

I wasn't sure if a "sticky" concept would add much functionality, because of my perspective (as shaped by necessity) of using module clear for system-level provisioning. But it's a reasonable design decision of what to expose to users. A "sticky" concept allows users to see not only names but also versions of modules so provisioned, and that could be useful in support inquiries. Importantly, a sticky concept opens the door to unload when desired, after all, which cannot be done for "disowned" modules.

Thus, I think there needs to be an override flag to unload and purge actions to affect sticky modules as well. Like in #268, a -f, --force option would mesh with Unix conventions. Could this work?

You gave -f already a meaning for unload and switch. Both require named modules, and implying unstick as well surely goes along with the user's expressed intention. By contrast, purge was not yet affected by -f, so that seems a reasonable addition.

Could a user want to module -f purge a botched lineup but want to keep "system"/"sticky" modules? If so, perhaps a different option than -f is needed after all, or -f be required to be doubled to overcome "sticky", similar in spirit of how -v, --verbose is treated in many applications.

[xdelaruelle]

Through the new module tag mechanism, 2 tags will have a special meaning: sticky and super-sticky. Both tags will forbid the unload of tagged module unless if this module is reloading. sticky modules will also be unloaded if the unload action is forced. Even if forced the super-sticky modules cannot be unloaded.