gen-class not generating a class - clojure

Question

I'm having difficulty referencing classes generated via :gen-class.
The smallest example I can show that demonstrates the problem is:
(defproject test-proj
:dependencies [[org.clojure/clojure "1.8.0"]]
:aot [test-proj.test])
(ns test-proj.test
(:gen-class))
(defn -main []
(println test_proj.test)) ; Error here
The problem is, this yields a ClassNotFoundException on the marked line.
(I tried all different combinations of - and _ in the above file and the project.clj. I still don't fully understand what requires an underscore and what tolerates a dash. Some things seem to roll with dashes and convert them as needed, whereas I know from messing around that in the -main, I need underscores to reference test_proj.test.)
If I go into the project root file, there's no target folder, so it's not generating the class. If I go into the terminal and run lein compile, it generates the needed classes under target, and the above code runs without error. This is a poor workaround though. What if I modify the file and forget to manually recompile it? It's also a pain to have to manually compile it after any time I do a clean.
As a shot in the dark, I tried using compile right underneath the ns macro:
(compile 'test-proj.test)
If I uses dashes, compile seems to do literally nothing. I may be misinterpreting its use, but it doesn't generate class files under target. If I use underscores, it gives an exception saying that the namespace isn't found.
Is there a way to have the classes generated automatically so I don't need to run lein compile everytime? I thought that that's what the :aot in the project.clj did.

Answer 1

With Leiningen, specify :aot settings. :all is the easiest.
project.clj
(defproject test-proj "0.1.0-SNAPSHOT"
:main test-proj.core
:aot :all
:dependencies [[org.clojure/clojure "1.8.0"]])
If you want, you can specify the exact namespaces in an array as seen below:
project.clj
(defproject test-proj "0.1.0-SNAPSHOT"
:main test-proj.core
:aot [test-proj.core]
:dependencies [[org.clojure/clojure "1.8.0"]])
Then the following lein command:
lein compile
Will generate the byte code and .class files as specified in the :aot settings above.
core.clj
(ns test-proj.core
(:gen-class))
(defn -main[]
(println test_proj.core)
(println "Hello, World!"))
You want to see something like the below:
NikoMacBook% lein compile
Compiling test-proj.core
Once this is done, check the target folder, contains the proper class file, here test_proj/core.class.
NikoMacBook% tree target
target
├── classes
│   ├── META-INF
│   │   └── maven
│   │   └── test-proj
│   │   └── test-proj
│   │   └── pom.properties
│   └── test_proj
│   ├── core$_main.class
│   ├── core$fn__38.class
│   ├── core$loading__5569__auto____36.class
│   ├── core.class
│   └── core__init.class
└── stale
└── leiningen.core.classpath.extract-native-dependencies
7 directories, 7 files
The following will run the :main namespace, so test-proj.core.
lein run
Will output
NikoMacBook% lein run
Compiling test-proj.core
Compiling test-proj.core
test_proj.core
Hello, World!
Note, that the class is calling itself. Note also that if you do not run lein compile beforehand , it will run by itself.