The following gist is the summary and solution from the discussions of https://groups.google.com/forum/#!topic/clojurescript/BEGF_AjSjmQ.
I wrote a macro in ClojureScript and wanted to test the macro by using println function
like this,
;; qna/macro.clj
(ns qna.macro)
(defmacro my-add [a b]
(println "a =" a "b =" b) ; <-- Here
`(+ ~a ~b))
;; qna/core.cljs
(ns qna.core
(:require-macros [qna.macro :refer [my-add]]))
(defn ^:export main []
(my-add 2 3))The source of project.clj and resources/public/index.html are like the following.
;; project.clj
(defproject qna "0.1.0-SNAPSHOT"
:dependencies [[org.clojure/clojure "1.9.0"]
[org.clojure/clojurescript "1.10.339"]
[philoskim/debux "0.4.12"]]
:min-lein-version "2.6.0"
:plugins [[lein-cljsbuild "1.1.7"]
[lein-figwheel "0.5.16"]]
:clean-targets ^{:protect false}
["target"
"resources/public/js/out"
"resources/public/js/core.js"]
:cljsbuild
{:builds
[{:id "dev"
:source-paths ["src"]
:compiler {:main qna.core
:output-to "resources/public/js/core.js"
:output-dir "resources/public/js/out/"
:asset-path "js/out/"
:optimizations :none
:source-map true
:pretty-print true} }]})
;; resources/public/index.html
<!doctype html>
<html lang="en">
<head>
<meta charset='utf-8'>
<title>QnA Demo</title>
</head>
<body>
<h2>QnA Demo</h1>
<div id="app"></div>
<script src="js/core.js"></script>
<script>qna.core.main();</script>
</body>
</html>When I open the above .html file in the browser, I encounter the following error.
Uncaught SyntaxError: Unexpected identifier in core.js:4And the compiled core.js file is like this.
// Compiled by ClojureScript 1.10.339 {}
goog.provide('qna.core');
goog.require('cljs.core');
a = 2 b = 3 // <-- embedded printed result
qna.core.main = (function qna$core$main(){
return ((2) + (3));
});
goog.exportSymbol('qna.core.main', qna.core.main);
//# sourceMappingURL=core.js.mapTo sum up, whenever I use println function within a macro for ClojureScript, the
printed result doesn’t go to the REPL but is embedded into the compiled .js file.
If this is a bug of ClojureScript, I will register this error in the ClojureScript JIRA.
You can use cljs.util/debug-prn if you need to print during macro expansion.
Whether or not this should be called a bug I don’t know.
;; qna/macro.clj
(ns qna.macro
(:require [cljs.util :as ut]))
(defmacro my-add [a b]
(ut/debug-prn "a =" a "b =" b) ; <-- Here
`(+ ~a ~b))
;; qna/core.cljs
(ns qna.core
(:require-macros [qna.macro :refer [my-add]]))
(defn ^:export main []
(my-add 2 3))$ lein cljsbuild once
Compiling ClojureScript...
Compiling ["resources/public/js/core.js"] from ["src"]...
a = 2 b = 3
Successfully compiled ["resources/public/js/core.js"] in 0.496 seconds.If you use my debux library, use dbg-prn function like this.
|
Caution
|
All the macros for ClojureScript are compiled by the Clojure compiler, not by the ClojureScript compiler.
So you have to use debux.core, not debux.cs.core, like the following.
|
;; qna/macro.clj
(ns qna.macro)
(use 'debux.core)
(defmacro my-add [a b]
(dbg-prn "a =" a "b =" b) ;; Use dbg-prn in debux
`(+ ~a ~b))
;; qna/core.cljs
(ns qna.core
(:require-macros [qna.macro :refer [my-add]]))
(defn ^:export main []
(my-add 2 3))You can see the printed output of dbgm only in the ClojureScript compiling process like this.
$ lein cljsbuild once
Compiling ClojureScript...
Compiling ["resources/public/js/core.js"] from ["src"]...
dbg-prn: a = 2 b = 3
Successfully compiled ["resources/public/js/core.js"] in 0.495 seconds.