@alexmiller Q about basis calculation: I'm not sure if this is a bug, but it caught me out (and was raised as a bug against depstar). If you call create-basis with :aliases, the :deps entry in the basis you get back does not reflect any :extra-deps in those aliases -- but it does reflect :replace-deps from those aliases. I was using that basis as the argument to t.d.a's sync-pom which only uses :deps and :paths when constructing the pom.xml file, so when depstar tried to create/sync a pom file, it looked as if :aliases were being ignored. My "fix" for this in depstar is to do the following:

(let [{:keys [resolve-args] :as basis}
          (t/create-basis (cond-> {:aliases aliases}
                            repro (assoc :user nil)))]
      (update basis :deps merge (:extra-deps resolve-args)))

In the tools.build guide, it seems to indicate that the :build alias would contain :deps {io.github.clojure/tools.build {:tag "v0.1.2" :sha "81f05b7"} -- is that something specific to -T? I would have expected :replace-deps {io.github.clojure/tools.build {:git/tag "v0.1.2" :git/sha "81f05b7"} for a tool (`:replace-deps` instead of :deps and :git/ qualifiers on the tag and SHA).

the :deps is coming from the merged deps.edn so is part of the input to the basis calculation

for the deps to use when writing a pom, you should really use the root deps from :libs (the output of the basis). I'm not sure what write-pom in tools.build uses, might be wrong there

:deps and :replace-deps have always been synonyms in aliases

we had basically switched to making :replace-deps the primary but when using it with -T, :deps makes more sense to me - this is something I'm still thinking about

yeah, write-pom is still using :deps. that's the bug imo. logged as https://clojure.atlassian.net/browse/TBUILD-3

Yay me! I found a bug 🙂 Thanks for the other answers. And the :tag vs :git/tag Q observation @alexmiller?

(I have hf.depstar.api/jar and hf.depstar.api/uber as drop-in replacements for the tools.build.api versions working locally -- still trying to decide whether I want to also expose the pom and aot stuff from depstar as drop-in replacements for tools.build.api/write-pom and tools.build.api/compile-clj since they have a number of additional knobs and dials over the built-in versions -- the API for those two functions is too different from how depstar currently works so I've cleaned up hf.depstar so that it can offer an alternative "build" approach via -X/`-T` or in a build.clj script... but now I need to write a lot more documentation!)