I'm writing a framework. Hopefully I'd like implementing projects to use the main method for the framework.
In my demo project, in definition.clj I have:
(ns definition
(:gen-class))
(def widget
{:this :that})
(defn -main [& args] (prn "MAIN"))
In my project.clj file I have :main ^:skip-aot definition. When I lein run I get the expected
lein run
"MAIN"
When I lein repl I can see the widget and -main functions:
definition=> definition/-main
#object[definition$_main 0x3ce2a73f "definition$_main#3ce2a73f"]
definition=> definition/widget
{:this :that}
When I call (all-ns) I can see the namespace as #object[clojure.lang.Namespace 0x64965348 "definition"].
Here's the problem: if I change the main method to that defined in another project (which is a dependency):
:main ^:skip-aot the-framework.core
The main method works. But the namespaces are no longer visible:
the-framework.core=> definition/widget
CompilerException java.lang.RuntimeException: No such namespace: definition, compiling:(/private/var/folders/gc/_1drfv2n2m588qnq5xz35g080000gn/T/form-init8820469930602256143.clj:1:1325)
The only thing that changed was the :main value in the Leiningen project.clj definition.
Is there a way to change the main method to an namespace not defined in the project without breaking the namespaces in the project?
Related
I have very strange Lein's behavior: it keeps loading unexisting old code.
There is src directory with something like src/service/api.clj and src/user.clj. All files under src/service are reloading, but lein totally ignores any changes in src/user.clj.
(ns user
(:require [ragtime.jdbc :as jdbc]
[ragtime.repl :as repl]))
...
(defn migrate []
(repl/migrate (load-config)))
Even if I delete migrate definition, REPL will have it in user namespace, lein will run it with lein run -m user/migrate after doing lein clean and will not load changes with (load-file "src/user.clj") too.
How to make it load my changes to user.clj ?
Lein only looks for code in source paths directories. If you don't have any specified then src is assumed. In your project.clj this would be the suggested entry:
:source-paths ["dev" "src"]
To be able to reload code from the REPL this will work for user.clj:
(ns user
(:require [clojure.tools.namespace.repl :refer (refresh refresh-all)]
[clojure.stacktrace]
[clojure.pprint :as pp]))
;;
;; To run open a REPL and:
;; (reset)
;; (core/migrate)
;; Repeat those two commands after every source code change you make
;;
(defn reset []
(refresh))
user.clj can go under the dev directory.
The answer to your question is I think that user.clj is supposed to be changed so infrequently that restarting the JVM/REPL is not an issue after you have made changes. Code that is being changed frequently should be under the src directory, and should not be named as namespace user. The main entry point code that you have typically goes in a file called core.clj. So you should put the contents of your user.clj file in the core namespace i.e. in a file called core.clj, which is placed under src.
When using Leiningen to create a project, does the core.clj file have to contain the -main function (the auto-generated one when the app is created) in order to run the program with the command lein run? Do all functions I create have to be called inside -main?
No, it does not have to be in core.clj. You can put your -main function wherever you like, so long as you tell lein where to look for it in your defproject in project.clj.
(defproject myproject "0.1.0-SNAPSHOT"
:main ^:skip-aot myproject.other-name-space)
This will tell lein to load myproject.other-name-space as its primary namespace when it loads the repl and when it looks for a -main class. If you have -main class in two places, lein will use the one you specify here in defproject. You do not need to place all your program code in the -main class, you simply use it as a starting point.
For the development of a library I started from a lein project, invoked like so:
lein new mylib
if I call lein install now, I can access my library in other projects. But trying to immidiately test the functions I wrote failed:
lein repl
...
(dir mylib.core)
Exception No namespace: mylib.core found clojure.core/the-ns (core.clj:4008)
Do I have to add something to the project.clj file maybe?
In order to use a library you must cause the code to be loaded - that it be on the classpath is not sufficient.
You can do this easily in an ns declaration in a file of course, but in the repl it can be easier to use (require '[my-lib.whatever :as w]) after which one can call (w/foo) (w/bar) etc. as expected. You can also use (in-ns 'my-lib.whatever) in order to switch to the namespace, but this will not give you a good result unless you have previously used require or use or load-file etc. to get the definitions first.
Let's say you created a new library named clj-foo.
% lein new clj-foo
Start your repl.
% cd clj-foo
% lein repl
In the repl, load the main entry point to your library and switch to its namespace.
(load-file "src/clj_foo/core.clj")
(ns clj-foo.core)
Now you're in the clj-foo.core namespace, make sure to add back in the repl ns to get things like doc available.
(use 'clojure.repl)
That's it. You're all set to start calling functions in your library. Note that other library files will be available from the clj-foo.core namespace if they were loaded by namespace declaration at the top of clj_foo/core.clj. If not, then you'll need to invoke load-file with their path as well.
If you make changes in core.clj. You can invoke load-file again to pick up the new code. As you progress, you can use cider to facilitate loading of individual functions and files. But that's for another question. :)
You need to add a dependency to use your library from another project. To do this add a vector (a tuple-2) to the vector that is the value of the :dependencies key in the project.clj file. Here's an example:
:dependencies [[org.clojure/clojure "1.7.0"]
[org.clojure/clojurescript "1.7.170"]
[org.clojure/core.async "0.2.371"]
[default-db-format "0.1.0-SNAPSHOT"]
[com.andrewmcveigh/cljs-time "0.3.14"]]
My own local library is called default-db-format. Its really no different to adding a dependency for com.andrewmcveigh/cljs-time.
As you say you can already do this, but are having trouble getting a REPL connection to the project of the library itself. When you go (in-ns 'some-path), you need the single quote in front of some-path. Note that some-path is a different thing to the name of your library.
Rather than use lein repl you can use the figwheel repl - if your project is setup with figwheel. My library has only one entry point and that is lein figwheel devcards. After that I had no problem going to a namespace and trying out a function:
cljs.user=> (in-ns 'default-db-format.core)
nil
default-db-format.core=> (check 1 2)
As noisesmith mentioned having a REPL in your IDE is the best setup. No fiddly typing just bring up pre-configured REPLs (per namespace) with the click of a button (or keystroke). Figwheel/Cursive setup instructions here.
I was also facing the same issue with the following configuration:
Leiningen 2.9.0 on Java 1.8.0_201 Java HotSpot(TM) 64-Bit Server VM
My file looks like this, and from the repl I desired to invoke the foo function
(ns cljtest.test
(:gen-class))
(defn foo [input]
(assoc {} "a" 123))
Both these approaches worked fine for me on the repl.
1)Switch to the appropriate name space:
cljtest.core=> (in-ns 'cljtest.test)
#object[clojure.lang.Namespace 0x90175dd "cljtest.test"]
cljtest.test=> (foo nil)
{"a" 123}
cljtest.test=>
2)Require the appropriate name space:
cljtest.core=> (require '[cljtest.test :as test])
nil
cljtest.core=> (test/foo nil)
{"a" 123}
cljtest.core=>
I have no trouble calling functions in lein repl from my namespaces when I have created a lein new app .... But I don't seem to be able to call functions in lein repl when I just create a library project via lein new .... Details follow:
When I create a lein app with, say lein new app my-app, and then, from the project directory (the directory that contains project.clj), I do lein repl. The repl leaves me in the namespace my-app.core
my-app.core=>
I can now call functions in the repl, even functions defined in side files.
my-app.core=> (-main)
; Hello, world!
my-app.core=> (my-app.anotherfile/foo)
; Hey, there; this is foo from anotherfile
so long as I :require [my-app.anotherfile] in the ns macro of core.clj.
Ok, great; now I would like to do similarly with a lein library. So I lein new my-lib, then lein repl, and I'm in the user namespace:
user=>
huh? Ok, well, my lib contains a function that I want to call (this is just the one that leiningen creates by default)
(ns my-lib.core)
(defn foo
"I don't do a whole lot."
[x]
(println x "Hello, World!"))
I try
user=> (in-ns 'my-lib.core)
my-lib.core=> (foo 42)
; CompilerException java.lang.RuntimeException: Unable to resolve symbol: foo in this context, compiling:(NO_SOURCE_PATH:1:1)
nope. How about this?
user=> (my-lib.core/foo 42)
; ClassNotFoundException two-files-lib.core java.net.URLClassLoader$1.run (URLClassLoader.java:202
aha! Different error, but still no cure in sight. lein compile and lein javac don't seem to do anything either.
I have been unable to find or deduce the correct incantations in the docs or online and would be grateful for advice.
In a default lein new project you need to require the namespaces you wish to use explicitly -- (require 'my-lib.core). in-ns simply creates a new empty namespace of the given name if it doesn't already exist, it doesn't load any code from the classpath.
App projects do this automatically and switch to the main namespace in the REPL task, because they have a :main foo.core entry in their project.clj by default. It's possible to do it for a library, but you shouldn't -- as a side effect, it causes AOT compilation of the main namespace, which is generally undesirable.
Instead, in lein2 you can use :repl-options {:init-ns my-lib.core}.
I'm a beginner with clojure, only starting it yesterday.
I have gathered that a simple way to create a standalone app is with leiningen lein new foo.
I tried to create a hello world test project with leiningen. I added :main and :aot directives to project.clj, added :gen-class to the core.clj file and tried lein run, but I get errors about class definition not found.
Exception in thread "main" java.lang.NoClassDefFoundError:
Caused by: java.lang.ClassNotFoundException:
at java.net.URLClassLoader$1.run(URLClassLoader.java:217)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:205)
at java.lang.ClassLoader.loadClass(ClassLoader.java:321)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:294)
at java.lang.ClassLoader.loadClass(ClassLoader.java:266)
The core.clj file
(ns test.core
(:gen-class))
(defn -main [& args] (println "Hello main"))
And the project.clj file
(defproject test "1.0.0-SNAPSHOT"
:description "FIXME: write description"
:main test.core
:aot [test.core]
:dependencies [[org.clojure/clojure "1.2.1"]])
Edit: After further testing, it seems like copying the project to my desktop works as is, which I think points to that the environment on my laptop is somehow borked, but I don't know how.
The environment on desktop is clojure from repositories and leiningen from AUR. On laptop the clojure is from clojure.org and leining is from github.
[UPDATE April 2013]
Leiningen 2, which has been officially released for some time, includes the concept of project templates. By default, Leiningen provides an app template that provides what you need out of the box. Try:
lein new app my-project
You will see that Leiningen creates the familiar project template, but also includes:
The default namespace of my-project.core as the :main entry in your project.clj file
The :gen-class form in the namespace declaration of my-project.core
A default -main function in the my-project.core namespace
For those who cannot yet use Leiningen 2, the lein-newnew plugin provides an equivalent experience under Leiningen 1.
[/UPDATE]
To build a project that, when run, prints "Hello World!", you'd do as follows (revision of your process above):
Setup
lein new my-project
cd my-project
lein deps
You should now have a basic structure in place and the Clojure jar in your lib folder.
Write a Function
Now edit src/my_project/core.clj with your editor of choice, adding the following below the (ns ...) form:
(defn -main []
(println "Hello World!"))
This function is inside your my-project.core namespace. To ensure this gets run as your main, let's add a gen-class parameter to your namespace definition at the top, so that it now looks like this at the top of core.clj:
(ns my-project.core
(:gen-class :main true))
So all together, your core.clj file looks like this:
(ns my-project.core
(:gen-class :main true))
(defn -main []
(println "Hello World!"))
Configure it as the Main Function
Once you've got src/my_project/core.clj edited as above, you need to tell Leiningen (the build tool) where the "main" function for your project lives. Here's an example defproject form that does this:
(defproject my-project "1.0.0-SNAPSHOT"
:description "My Project"
:dependencies [[org.clojure/clojure "1.2.1"]]
:main my-project.core)
Now the -main function inside my-project.core becomes the entry-point for your program.
Run It
You can now have two options for running this project:
Use lein run at the command-line while at the root of your my-project project
Create a standalone jar file by running lein uberjar. You can then run the resultant jar file by running java -jar my-project-1.0.0-SNAPSHOT-standalone.jar
Figured it out. I had the latest leiningen from git, which was borked somehow. I checked out the 1.6.1 tag and ran self-install, and now it works.
I missed it, You named your project test, you can't do that change the name to something else it will work.
You say above
lein new foo
what you mean is
lein new test