Compilation breaks down in recent versions when changing CLJC file

[mtruyens]

Since a few versions, I get the error below when changing a CLJC file. I then have to kill Shadow-cljs, clean all directories, and restart it. (Note that I have quite some macros in my fairly large and complex code base, whereby the the macros affect both CLJS and CLJ files.)

No problems occur when changing only CLJS files.

I had to downgrade to the last version that worked perfectly, 2.8.93. If I recall correctly, the problem started somewhere around version 2.8.100, and the most recent one 2.9.0 also exhibits the problem.

Note that the error message about the redefining of a constant makes no sense. (Which is also evidenced by the fact that recompiling after cleaning the folders works fine. As does advanced compilation using lein-cljsbuild.)

Compilation failed!
Multiple files failed to compile.
------ ERROR -------------------------------------------------------------------
 File: /Users/mtruyens/symposix-stable/src-cljc/sx/cljc/utils/misc.cljc:11:1
--------------------------------------------------------------------------------
   8 |             #?(:clj  [clj-time.core :as clj-time]
   9 |                :cljs [cljs-time.core :as clj-time])))
  10 | 
  11 | (def ^:const app-title "ClauseBase")
-------^------------------------------------------------------------------------
Error in phase :compilation
Can't redefine a constant at line 11 sx/cljc/utils/misc.cljc
--------------------------------------------------------------------------------
  12 | 
  13 | (def ^:const docx-mimetype (str "application/vnd.openxmlformats-officedocument"
  14 |                         ".wordprocessingml.document"))
  15 | 
--------------------------------------------------------------------------------
------ ERROR -------------------------------------------------------------------
 File: /Users/mtruyens/symposix-stable/src-cljc/sx/cljc/lang/numerals.cljc:8:1
--------------------------------------------------------------------------------
   5 |             [sx.cljc.utils.string :as ustr]
   6 |             [clojure.string :as str]))
   7 | 
   8 | (declare ordinals cardinals)
-------^------------------------------------------------------------------------
Error in phase :compilation
Can't redefine a constant at line 8 sx/cljc/lang/numerals.cljc
--------------------------------------------------------------------------------
   9 | 
  10 | ; ----------------------------------------------------------------------------------------
  11 | 
  12 | (defn- nr->reverse-grouped-per-three
-------------------------------------

[thheller]

I would strongly advise not using ^:const to begin with. It is buggy in all sorts of weird ways.

Beyond that this error is coming from the CLJS compiler. shadow-cljs version 2.8.101 bumped the clojurescript version from 1.10.597 to 1.10.741 so I'm guessing that is the shadow-cljs release where this started breaking for you?

PS: I can't reproduce with a local .cljc file.

[mtruyens]

That's the first time I hear from this buggy behaviour, thanks! (Is it related to the warning made regarding the caching behaviour at the bottom of https://blog.fikesfarm.com/posts/2017-06-28-clojurescript-const-var-inlining.html ?)

Anyway, you seem to be right, because removing the ^:const does seem to remove errors (I have to comb through my entire code base, however).

The problem is, from my perspective, unrelated to the ClojureScript version. Both 1.10.597 and 1.10.758 work nicely with Shadow-cljs 2.8.93, even when changing those CLJC versions.

[mtruyens]

Addendum: all ^:const declarations removed from my code base, and the error is indeed gone. Thanks!

[thheller]

Well, the post you linked would be describing one of the bugs IMHO. I consider it a bug since the behavior is different from Clojure, not sure why that was added.

$ clj
Clojure 1.10.1
user=> (def ^:const x 1)
#'user/x
user=> (case 1 x true false)
false

$ shadow-cljs node-repl
shadow-cljs - config: /mnt/c/Users/thheller/code/shadow-cljs/shadow-cljs.edn
shadow-cljs - connected to server
cljs.user=> (def ^:const x 1)
#'cljs.user/x
cljs.user=> (case 1 x true false)
true