Is 3) meant to include situations where you have a "scratch" REPL running just to try stuff out (e.g., helping beginners on Slack) and it would be less convenient to restart that REPL with difference deps rather than just adding a lib to the REPL? For me, such situations are usually not accompanied by deps.edn at all.

you always implicitly have a deps.edn, even if it's just including clojure from the system deps.edn

sounds like a mixture of 2 and 3

Well, yeah, I meant the "project" (current directory) one. Libraries that I use add-lib for wouldn't generally go in either of the other files.

I have a scratch directory that has deps.edn with {} in it and I usually start a plain REPL with -Sdeps on the command-line, but if add-lib was easier to use, I'd just start that plain REPL and then add-lib in anything I wanted to experiment with and just leave it running (instead of restarting with different deps).

For me it would be mostly 1), especially in the early stages of a project I want to be able to add dependencies without having to restart the process. It could also be 2) if it's a lib I haven't used before, to be able to quickly evaluate it before committing to it.

by which you mean you would have a lib that called add-lib?

Yeah. Although essentially it's a library of things you'd do at the repl. I can't remember the details of why I was doing this now. Possibly to keep things "light" at someone's request, or maybe because I wanted to load things for dev time based on the config.edn

tests

not sure what that means? you add tests and rely on that failing later to tell you to add the lib?

yes, not a perfect solution, but covers most of the problems something like Could not locate chesire/core__init.class, chesire/core.clj or chesire/core.cljc on classpath. usually is enough to remember what went missing

Yep, pretty much the same thing as @U04V4KLKC. If the lib ends up getting used in the project, it will get added to a namespace's :requires. This will cause the project to fail CI tests if someone forgot to add it to the deps.edn.

remember later

For 1) I do it at the same time because it's a deliberate act. For 2) I do it later, once I've decided whether the lib is really what I need (so, yeah, I run the risk of forgetting but if I really need the lib, it'll end up required in the code base somewhere so tests will fail if I have forgotten to add it).

yes, I'm aware. investigating alternatives, making tables :)