Neither conda nor npm does something like that. They set up a localized environment, insulated from the host os installed software as far as packages they manage are concerned.

That is exactly what I mean by bypassing the operating system's software management subsystem. No software or configuration should ever be installed by anything other than the operating system's software management subsystem. It is the responsibility of the developer (you or anyone else doing so) to convert content pulled in by npm or anything that is not an OS package into one, but the best solution is to fix it upstream by abolishing these parallel software management subsystems, and automatically generating native OS packages for the software through continuous integration build processes.

Not doing so puts the onus on the consumer of the software, and to wit, the purpose of software is to make it easier, not harder or more time consuming, to do something. Imagine forcing the system administrator to have to replicate your development environment, through any mechanism, just to be able to run your application and all her dependencies, when she or he could have just plugged in OS packages of your software into the OS provisioning repository.

Feel sorry for you. But I have to maintain two projects, one requires an older version of the library, one requires the newer. There is no way to achieve this with "apt-get" or "yum".

Actually, yes there is: make the library interfaces versioned, and fuse them into one library for all versions of the consuming software. This is, post action, considerably more work, but that is what developing software is all about. The idea of versioned interfaces is not new, and originates on UNIX. Since the initial topic of discussion is building and linking libraries in C, the link editor can consume linker map files, which define the library's semantics based on the version of the interface, and will encode this information into the executable and linking format header of the binary. The encoded information will be consumed by the run time linker in order to present the correct version of the interface to the consuming application. Same principle applies to any software in any programming language.

There are many packaging systems for Linux/BSD/Unix I use often (apt/deb, yum/dnf/rpm, pacman, ports, brew, cygwin), even more repositories (ubuntu, debian, ...) and there is absolutely zero chance that I can rely on dependencies to be provided by the OS package manager - they don't update at the same rate, and sometimes not in a compatible way (e.g. PIL vs. Pillow migration for Python; ffmpeg vs libav).

Then the developer must provide the additional dependencies as OS packages, and can do so without interfering with the OS vendor by adhering to the System V / Linux Standards Base - Filesystem Hierarchy Standard: by delivering the payload in /opt[/namespace], the configuration in /etc/opt[/namespace], and coding the application to use data from /var/opt[/namespace]. The fathers of UNIX considered this, and provided specifications to address it accordingly.

http://refspecs.linuxfoundation.org/fhs.shtml

What you are suggestion is useless in my situation, and for at least 95% of the developers and deployment situations I'm familiar with.

As you can probably imagine, I disagree vehemently with your assertion, and it is my hope that through this dialog, I've managed to illustrate the reasons because of which that is so, as well as provided practical solutions to the problem at hand.

If it works for you, then ... good for you. But you're pretty unique.

You mean, I am unique in wishing to deliver software to the highest standards of quality enabled by our current technology? Having started as a system administrator, being a developer, I can completely understand the gargantuan amounts of work system administrators face trying to make developers' work repeatable, essentially being forced to complete developers' work for them. And that is simply not just, nor is it right. We as developers should do that.

Empathy is a core engineering value:

https://www.listbox.com/member/archive/182179/2013/05/sort/t...

respect your users and empathize with them. If you don't quite know how to solve the problem, ask system administrators to help you produce higher quality software, or even better, learn system administration yourself, just don't punt on the problem because you perceive it as too much work.