Add support for lein 2.7's :managed-dependencies

[cprice404]

In lein 2.7.0, a new feature was added that allows you to specify dependency versions in a new :managed-dependencies vector, so that you can, e.g., inherit dependency versions from a parent project (via the lein-parent plugin, etc.).

For more info see the Managed Dependencies docs in the lein repo.

The current release of lein-cljsbuild won't work with projects that use this, because the version checks at startup assume that they will be able to find the dependency version numbers directly in the :dependencies vector.

This commit adds support for getting the dependency versions via the new mechanism. It should be 100% backward compatible but it does introduce a min-lein-version of 2.7.

Opening this to solicit feedback. If there's another way to structure this in order to deal with the min-lein-version issue, let me know and I'll be happy to re-work it.

[danielcompton]

Can you check if this var exists before calling it? If it does then use it, if not then fall back to the old behaviour?

[cprice404]

@danielcompton sure, I've updated the PR based on your suggestion.

I'm still in the process of verifying these changes against a local clojurescript project that uses :managed-dependencies - will add another comment here when I've confirmed it's working properly. Just wanted to get this up for some early review and see if it seemed like a generally acceptable patch.

[mneise]

@cprice404 This looks good so far, would be happy to merge this 👍 Let me know when you think it's ready.

[cprice404]

Thanks! I got sidetracked today so didn't finish my testing, hope to finish it tomorrow.

[cprice404]

OK, done testing, confirmed that these changes work fine with my project, which uses :managed-dependencies heavily.

[mneise]

@cprice404 I tested your patch with Leiningen 2.6.1 and get the following exception:

clojure.lang.Compiler$CompilerException: java.lang.RuntimeException: No such var: classpath/merge-versions-from-managed-coords, compiling:(leiningen/cljsbuild/subproject.clj:78:16)

I get the exception because it's still trying to compile the then branch and then can't find the var. To make it work you need to write a macro where you check for the var and return the code that should be used to get the dependencies 😉

[cprice404]

Well, darn.

I could write a macro or I change the if to an if-let and then call the function via the resolved variable. The latter seems less messy to me but I'm fine doing it either way, so if you prefer the macro let me know.

[mneise]

I don't have a preference, I think both approaches are ok. If you prefer the if-let approach, then go for it 😉

[cprice404]

cool, working on it now. and testing with lein 2.6 this time :)

[cprice404]

pushed up that change.

[cprice404]

@mneise does this approach look OK?

[mneise]

Thank you for this 👍