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I have a project created using leningen in which I've saved clj files in the src/some_project_name directory (alongside the autogenerated core.clj file).

Also saved with these clj files are text files which I want to slurp from the clj files they live beside. My understanding is that reading files is relative to the working directory, and that the working directory will be wherever you've started the REPL from. I started the REPL from inside src/some_project_name where all the files are located, rather than root. (System/getProperty "user.dir") confirms this is the active directory.

However I've also read that slurp will look for files relative to your root directory, which is apparently what is happening despite starting the REPL from within src/some_project_name. I have to list the text file paths relative to the root directory in order for them to be found, e.g. "src/some_project_name/foo.txt" rather than just "foo.txt".

Before setting up a project, files were accessible relative to wherever the REPL was running (as I would expect). Now after setting up a project, they seem to only be accessible relative to root, regardless of where the REPL is started.

I have no problem with this, but I don't understand it. Is there some setup done by leningen that intercepts REPL evaluation and tells it to search from root rather than where the active directory is?

Solaxun
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1 Answers1

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I believe Leiningen REPLs use the project root as their working directory. (If not trampolined, they use a subprocess with the expected working directory – try jps -l after a lein repl, you should see two clojure.main processes.)

On a separate note, you may want to use clojure.java.io/resource to load files using classpath-relative paths. Such files would typically be placed in a resources folder – with Leiningen, this will typically be a sibling to src.

For example, if you place foo.txt in resources/some_project_name, you should be able to do the following:

(require '[clojure.java.io :as io])

(slurp (io/resource "some_project_name/foo.txt"))
Michał Marczyk
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  • Thanks for the reply - this reiterates what I suspected (REPL is relative to root) but doesn't really tell me why it's the case if you start it from somewhere other than root. I appreciate the tip on using the resources folder - I'm curious, what's the advantage there other than convention? I tried to scour the docs but discussion around resources / classpath-relative paths is a bit scarce. Thanks again. – Solaxun Jun 14 '17 at 16:10
  • Not sure if you're asking how this is implemented or why it is designed in this way. If the former, REPLs get their own JVM processes, so Leiningen just needs to launch those JVMs in the right directory. There's a namespace dedicated to setting such things up in the leiningen-core subproject (`leiningen.core.eval`). If the latter, I might conjecture that this is to ensure that the effects of your Leiningen commands are consistent regardless of any accidents of your shell's current working directory (as long as it stays within the project). – Michał Marczyk Jun 14 '17 at 17:46