Question

The point of this question is to clear up confusion about Clojure project.clj dependencies and how to specify a local dependency.

I have a bunch of Clojure lein projects in a tree

./projects/clojure/bene-csv # A csv parsing library
./projects/clojure/bene-cmp # A main program that depends on bene-csv

I’m editing bene-cmp’s project.clj file. I want to make a dependency to
./projects/clojure/bene-csv/bene-csv-1.0.0-SN.jar .

Do I use simple directory notation to specify the path or something else

Thank you.

Edit:

I can include bene-csv in my project by entering lein install in the bene-csv project directory, and using these project.clj entries in bene-cmp’s project directory’s project.clj file:

(defproject bene-cmp "1.0.0-SN"
  :description "This is the main benetrak/GIC comparison program."
  :dependencies [[org.clojure/clojure "1.3.0"]
                 [clojure-csv/clojure-csv "1.3.2"]
                 [bene-csv "1.0.0-SN"]])

However, I am still trying to figure out what the path is, and would appreciate any pointers or help along those lines. Thank You.

Answer 1

Leinigen uses maven dependency management under the covers, so all dependencies get installed in

${HOME}/.m2/repository/${groupId-as-path}/${artifactId}/$[version}/${artifactId}-${version}.jar

where for [org.clojure/clojure "1.3.0"] groupId is org.clojure, artifactId is clojure and version is 1.3.0. groupIds are converted to paths, so a groupId of org.clojure has a path of org/clojure.

In a maven dependency, specified in pom.xml, this would look like:

<project>

    ...    

    <dependencies>
        <dependency>
           <groupId>org.clojure</groupId>
           <artifactId>clojure</artifactId>
           <version>1.3.0</version>
       </dependency>
    </dependencies>

    ...

</project>

Note – If no groupId is specified then leiningen uses same value for both the groupId and artifactId.

The benefit of using maven dependency management is that it handles transitive dependencies for you, ie. if you specify a dependency on something, you get all the things it depends on and all the thing that those things depend on etc etc.

So to depend on a local project, the correct thing is to install the local project in your local repository.

To save you changing your versions endlessly while in a development phase, maven supports SNAPSHOT dependencies, whereby some extra information is appended to the version (the datetime basically) and maven knows, that for say 1.3.1-SNAPSHOT it should look for the latest version of that snapshot. This is triggered by the naming convention of {version}-SNAPSHOT.

You can, in maven, specify system dependencies with a hard coded path but generally that’s bad practice – it’s usually used for things that are platform dependent, i.e. may have a native library component.

By default maven central repository is searched, and leinigen adds in the clojars repository, which serves as a central repo for clojure jars.

leinigen uses this stuff under the covers and builds a classpath referring to the jars in your local maven repository.

Note that you can generate a pom.xml from a leinigen project with lein pom. You could then drive maven from that. A useful feature is

mvn dependency:tree

which gives an ascii art represenation of all the dependencies.