AOT compilation sometimes results in extra classes for already compiled namespaces

Question

Case-in-point: clojure/tools.logging.

Repro:
- AOT compile all the namespaces in clojure/tools.logging (clojure.tools.logging & clojure.tools.logging.impl)
- With the result on the classpath, AOT compile clojure/java.data (clojure.java.data)
- Observe clojure/tools/logging$eval32$fn__33.class in the output of the second compile (make sure to have different output directories for the two compiles).

This is normally harmless, but becomes an issue if you try to cache AOT compilation output. When you try to cache previous AOT runs this way, you sometimes end up with two otherwise unrelated namespaces generating the same filename. If these had the same contents that would be fine, but there's no guarantee that they have the same contents (since 32 & 33 there are just (gensym)s). Depending on which one "wins" in a classpath this could end badly.

I'm not an expert here, but it would be nice if these "extras" were either generated as part of tools.logging or were somehow aliased into the namespace they were compiled from (e.g. clojure/java/data/$clojure$tools$logging$eval32$fn__33.class or clojure/tools/logging/$clojure$java$data$eval32$fn_33.class).

Answer 1

Comment made by: hiredman

tools.logging uses eval to generate some code only when certain classes are present on the classpath, eval generates class files, when you have aot compiling turned on, those class files will be output to the filesystem.

the reason the name is the way it is, is because the eval happens when the tools.logging namespace is loading, so the value of the ns var is the tools.logging namespace, which is what the compiler is generating the name from.

Answer 2

Reference: https://clojure.atlassian.net/browse/CLJ-1916 (reported by alex+import)