ClojureScript :preloads doesn't work with just cljs.main --repl

Wed, 24 Dec 2025 15:13:56 +0000

Running cljs.main with just --repl doesn't preload whatever is on :preloads.

Given that the quickest way of trying ClojureScript is by running a command like :

clj -Sdeps '{:deps {org.clojure/clojurescript {:mvn/version "1.12.134"}}}}' -M -m cljs.main --repl

it would be great (and I think expected) to be able to run a repl with some dev tooling, like :

clj -Sdeps '{:deps {org.clojure/clojurescript {:mvn/version "1.12.134"} binaryage/devtools {:mvn/version "1.0.7"}}}}' -M -m cljs.main -co '{:preloads [devtools.preload]}' --repl

but it doesn't work.

It reads the file (it complains if you misspell the preload namespace) but then nothing gets loaded.

The problem seems to be related to ClojureScript not compiling the preload namespace when you run with just --repl

If you create a small single file project (like on the start guide) and then do :

clj -Sdeps '{:deps {org.clojure/clojurescript {:mvn/version "1.12.134"} binaryage/devtools {:mvn/version "1.0.7"}}}}' -M -m cljs.main -co '{:preloads [devtools.preload]}' --compile hello-world.core --repl

it works.
After the compile generates the out folder you can run just with --repl and the preload will work.

Proper deps.edn config with -co option of cljs.main

Thu, 09 Jul 2020 15:55:05 +0000

Hello,

I am trying translate the following cljs.main options with the CLI:

$ clj -m cljs.main          \
      -d public/js/compiled \
      -o public/js/main.js  \
      -O advanced           \
      -c hello-world.core

Into deps.edn:

{:deps {org.clojure/clojurescript {:mvn/version "1.10.764"}
        reagent {:mvn/version "1.0.0-alpha2"}}
 :main "hello-world.core"
 :optimizations :advanced
 :output-dir "public/js/compiled"
 :output-to "public/js/main.js"}

Then execute it with:

clj -m cljs.main -co deps.edn

However, it doesn't seem to work.

I also get the following error using the generated main.js file:

main.js:314 Uncaught TypeError: Cannot read property 'mg' of undefined
    at Mb (main.js:314)
    at Tn (main.js:699)
    at Rn (main.js:698)
    at Nn.h.Me (main.js:718)
    at Function.Wn.A (main.js:710)
    at Nn.h.Le (main.js:718)
    at Function.Wn.j (main.js:710)
    at ep (main.js:761)
    at main.js:761

Some thoughts

Am I missing a CLI option? or deps.edn key/value pair?
Am I using it wrong; the CLI or deps.edn or both?
Or is it not well supported at the moment so I should just stick with the CLI?

Clojure Q&A - Recent questions tagged cljs.main

ClojureScript :preloads doesn't work with just cljs.main --repl

Proper deps.edn config with -co option of cljs.main