/scratch-ring-proxy-issue

Primary LanguageClojure

Problem Statement

I'm perpplexed by the behaviour I see here.

Try the following:

  1. Run lein repl

  2. Try to (require 'compojure.handler) -- you should get the following error:

    CompilerException java.lang.IllegalAccessError: assoc-conj does not exist, compiling:(ring/middleware/multipart_params.clj:1:1)

  3. Now comment out the dependency on ring-proxy in project.clj (line 8) and try it again, note that there's no error.

How is it that ring-proxy is interfering with the ability to require compojure.handler? I've noticed that the ring-proxy jar contains 1.3MB worth of stuff, it seems to me like a ~60 line clojure lib should produce a much smaller jar, but I'm at a loss to explain why this happens.

Explanation

This is apparently because of AOT (ahead of time) compilation. By default, when you compile a clojure library, you'll just end up with a .jar file that depends on the clojure runtime, and contains a bunch of .clj files. However, if you specify a main method (as ring-proxy has done here), you'll get a bunch of funky .class files instead. It looks to me like there is some transitive AOT compilation happening, and we're also getting class files for the dependencies of ring-proxy.

The whole thing is complected by a couple of other factors:

  • In this project we're depending on compojure 1.1.6, which depends on ring 1.2.1, but ring-proxy depends on ring 1.1.8.
  • In ring 1.1.8, assoc-conj was in ring.util.data, in ring 1.2.1 it was moved to ring.util.codec

What happens is that when we depend on ring-proxy, even if we try to exclude the ring dependency, some ring 1.1.8 code is included because of the (transitive?) AOT compilation, which means that assoc-conj isn't in the namespace where expect to find it.

I don't think I'm completely clear of all of the details of what's going on here yet, but I think I've got the gist of it.

Possible Solutions

  • Remove any dependencies on ring 1.2.1, only depend on ring 1.1.8 (depending on the project, this can be as easy as rolling back to compojure 1.1.5 instead of using 1.1.6)
  • Work out a patch for ring-proxy that somehow avoids AOT compilation. Maybe this means moving their standalone server to it's own project.
  • Others?