On Wednesday, June 21, 2017 at 9:42:00 AM UTC-5, Didier wrote:
>
> I think I answered myself, looks like it does here:
>
> try {
> Var.pushThreadBindings(
> RT.mapUniqueKeys(CURRENT_NS, CURRENT_NS.
> deref(),
> WARN_ON_REFLECTION,
> WARN_ON_REFLECTION.deref()
> ,RT.UNCHECKED_MATH, RT.
> UNCHECKED_MATH.deref()));
> loaded = (loadClassForName(scriptbase.replace('/',
> '.') + LOADER_SUFFIX) != null);
> }
> finally {
> Var.popThreadBindings();
> }
>
>
> So now I understand, but I wonder if it makes sense. 99% of the time, it
> won't be an issue, but if you're doing anything with *ns*, you'll run into
> a situation where if you compile and bootstrap yourself through gen-class
> or clojure's java API, your code will not behave similar to when you're
> loaded at runtime or bootsraped through clojure.main or lein.
>
It would be helpful to be clearer about what you mean with these different
cases as it's ambiguous to me at least. I think you mean:
1. "compile and bootstrap yourself through gen-class" means: you generate a
class and then invoke the main() method of that class
2. "loaded at runtime" means: you (presumably) start the REPL, load a
namespace (either from a source file or a class file), then invoke the
-main function
3. "bootstrapped through clojure.main" means: you invoke clojure.main (a
compiled program provided with Clojure) with the -m arg specifying a
namespace. This will start the Clojure runtime, load the namespace, then
invoke the -main function
4. "bootstrapped through lein" means: I assume this is "lein run" with a
:main set or "lein run -m" but I think lein supports specifying a namespace
or a function in a namespace or a class with a main() method. Depending
which of those you're doing, this is like similar to either #1 or #2 and
here lein is effectively doing similar work as #3.
5. There is a Clojure Java API (http://clojure.github.io/clojure/javadoc/),
but I'm not sure if you are actually referring to this or something else.
Doing so would basically mean going through that API to do the same thing
as #2.
>
> (ns dda.main
> (:gen-class))
>
> (def should-exist "Do I exist?")
>
> (defn -main []
> (in-ns 'other)
> (ns-name *ns*))
>
> A bad example, but this code will work through lein, clojure.main, and
> when loaded from a REPL, but not when started from gen-class or Clojure's
> java API. Is there a good reason for the discrepancy?
>
You are doing different things, and thus experiencing different results, so
in some sense I would expect them not to be identical. In particular, both
#3 clojure.main and #4 Leiningen are effectively programs wrapping your
program - since you're using a wrapper, you should expect that wrapper to
do more stuff and have an effect on your runtime environment. What I think
maybe is interesting here is the difference between invoking a main()
method first vs loading and invoking the function from the Clojure runtime
(#1 vs #2). There you see that some things are bound in #2 that have not
yet been bound in #1. More below at the end.
> Shouldn't all methods to bootstrap your code start out with an equal
> initialization scheme?
>
Maybe. We are also interacting with the host initialization here and that
complicates things. The only way to start a Java program is ultimately to
specify a class with a main() method, so that's a constraint we have to
deal with.
> I would suggest that Clojure's java API (which I assume gen-class uses
> under the hood)
>
Again, I'm struggling to connect "Clojure's Java API" here to what that
means to me. gen-class is not involved at runtime - it's compile-time
functionality that produces a class file. That generated class file uses
the *Clojure runtime* to load and invoke Clojure functions. Most of that is
exactly the same as what happens when running typical Clojure functions.
The part that's different is that there is some additional scaffolding
created to handle the namespace-level effects when loading AOT classes.
> should also initialize the common bindings and set the namespace to user.
> That way, all entry point always behave similarly.
>
I think if I were to restate your suggestion, I would say that a
genclass-compiled main entry point should initialize the Clojure runtime
and invoke the code in a binding as if it were being invoked from other
Clojure code. I can see some logic in that (although that then also affects
#3 and #4 as they go through this code too).
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