> It seems to me that it's good to have shim programs that satisfy
> dependencies of apps on systemd, each shim performing some systemd
> function. Here's why:
>
> Suppose there are 10,000 application programs (apps) for Linux,
> and their developers foolishly insert dependencies on systemd.
>
> If Devuan developers write 50 simple shims to fulfill those
> dependencies, then Devuan users can run those 10,000 apps
> as they are, directly from the Debian repos. And when the
> apps are updated, they will still run.

As pointed out already, unless the systemd calls are not actually doing anything useful to the operation of the program then replacing each call with a "null operation" will break the program.

But, IMO there is a more important philosophical reason not to do it.

If it were technically possible to create all these shims that would "do nothing but magically still let programs work", by doing it that way you have "legitimised" the use of those systemd calls. As in, "use as many as you like, it doesn't actually matter".
If Devuan can get to the point where the devs that are "blindly going down the systemd alley"* want to get on board, without these shims there is a clear message - fix your code or it can't be installed.

* I'm sure some feel they are using systemd calls for a good reason. In many cases there may well be merit in using them when available.


As an example, I tried to upgrade one of my Wheezy systems to Jessie with *systemd* pinned as not installable. It took a bit of messing around figuring out what the broken dependencies were, and in the end I only had ONE single package that I needed and which wouldn't install - clamav-daemon (the other clamav* packages were fine, just not that individual one). In response to my messages on the clamav mailing list and bug report, it turns out that they only make ONE call to libsystemd during startup and then never use it again, and it's not even an essential call - but no, it would be a "waste of CPU cycles" to do a "if exists libsystemd0 then call ..." I assume it's not considered a waste of cycles to maintain a separate package for Wheezy security updates !
If you provide a shim, then you legitimise this sort of behaviour. Which would you prefer : a clamav-daemon package with a dependency on a "fake" libsystemd0, or a clamav-daemon package without any systemd dependency ? If you legitimise using shims, then the same people that see no reason to not hard-depend on libsystemd0 will bring you a package with a hard-depends on fake-libsystemd0.