configuring lein-tools-deps as a plugin breaks the lein-zprint plugin

[kkinnear]

I am the maintainer of lein-zprint, and it turns out that if you have lein-tools-deps and lein-zprint both as plugins to Leiningen 2.8.1, lein-zprint doesn't work. This issue describes the problem, and this repo demonstrates the problem.

Nearly as I can tell, because lein-tools-deps is built with Clojure 1.9, it is causing the lein-zprint (and the underlying zprint library) to fail because lein-zprint is built with clojure-future-spec, which kind of "gets out of the way" of Clojure 1.9. At least when I clone and build lein-tools-deps with Clojure 1.8, lein-zprint works fine, and when I build lein-tools-deps with Clojure 1.9 as a :provided dependency, lein-zprint works fine. I have no idea if either of these things broke lein-tools-deps because I don't really know how to use it myself.

The root of all of this is that Leiningen doesn't yet support Clojure 1.9 plugins -- as this issue notes. I'm not expecting that to change anytime real soon. If it were possible for lein-tools-deps to be built with Clojure 1.8 that would certainly solve the problem. I think that when running as a Leiningen plugin it is running with Clojure 1.8 anyway, so that there is little loss in showing that as a dependency. But I could be wrong, I'm not super experienced in Leiningen plugins.

Anything help you could provide would be appreciated!