> there's no way to list the dependencies of an SBT project (in order to set up an offline sandbox, in our case for reproducible building with Nix)

Well, the same is true for Maven. I know because I've tried. Plugins can download arbitrary dependencies at execution time.

That's where the point about Rice's theorem falls apart: it applies as much to maven as to Gradle because maven plugins can do whatever they want.

But that can't be runtime dependencies to your code?

I've written a couple of Maven plugins and you must declare your dependencies explicitely even for those. Pulling in stuff dynamically would be possible but not very clever.

The maven surefire plugin downloads dependencies dynamically depending on the kind of tests it finds. Is it not very clever? I agree. But it's one of the most popular maven plugins.

That sort of thing is unfortunate, but not too bad since we can add those packages to our own dependency list (e.g. in the pluginManagement section). It's a bit redundant, but as a bonus it ensures that such "dynamic" behaviour is acting as expected (since the build will fail if it picks different packages to the ones we wrote down!)

The same approach can be used when depending on third-party jars/plugins which don't fully specify their dependencies: just add the missing ones as extra dependencies of our project. (This happens a lot, where projects have undeclared dependencies on some commonly-used library, and don't notice since it's usually available in a well-stocked ~/.maven2 cache)

During Maven build, sure. But it does not add unknown dependencies to your code at runtime.

I am used to classpath problems with surefire but that it downloads undeclared stuff is new to me. Afair it pulls only in transitive dependencies. Could you give an example?

I am mainly building war files and it turned out to be good practice to explicitely declare any ambigous transitive dependencies. There's even a Maven plugin which shows up classes with different hash during build, https://basepom.github.io/dependency-versions-check-maven-pl...

"Runtime" was imprecise, I meant at build execution time. The point being that you can't pre-download the dependencies without executing the build.

Yep, SBT and Gradle make Maven look good.

Gradle is declarative. The 'code' you write does not conduct the build; it assembles an object graph which describes the build, much like the one you get from parsing the Maven XML. The advantage of using code for this is that you the description can be more concise, expressive, etc. But once it's run, the graph is built, and you can explore that, list dependencies, etc, quite safely.

> Gradle is declarative

Gradles own docs say "Well-designed build scripts consist mostly of declarative configuration rather than imperative logic".

When it's up to the programmer to make a script declarative, it's not a declarative language.