Bugs with prefix namespaces & co.

[green-coder]

Minimal project to reproduce it: https://github.com/green-coder/shadow-cljs-namespace-party

shadow-cljs watch app

Then go to http://localhost:3000/

2 problems:

• one is the error displayed,
• the other one is the nil value printed.

[thheller]

You get a warning for this?

------ WARNING #1 - :ns-var-clash ----------------------------------------------
 File: /mnt/c/Users/thheller/code/tmp/shadow-cljs-namespace-party/src/a/b.cljs:3:1
--------------------------------------------------------------------------------
   1 | (ns a.b)
   2 |
   3 | (def c "c")
-------^------------------------------------------------------------------------
 Namespace a.b.c clashes with var a.b/c
--------------------------------------------------------------------------------
   4 |
--------------------------------------------------------------------------------

This is a known limitation in CLJS and not shadow-cljs related at all.

[thheller]

For the charset warning add <meta charset="utf-8"> to your html head.

[thheller]

FWIW Chrome shows a better error. Not sure why Firefox does not show the actual error message on load.

[green-coder]

None of compile and watch had shown any warning with v2.12.5 :

➜  shadow-cljs-namespace-party git:(master) shadow-cljs compile app
shadow-cljs - config: /Users/vincent/code/nws/shadow-cljs-namespace-party/shadow-cljs.edn
shadow-cljs - starting via "clojure"
WARNING: When invoking clojure.main, use -M
[:app] Compiling ...
[:app] Build completed. (46 files, 0 compiled, 0 warnings, 1.35s)
➜  shadow-cljs-namespace-party git:(master) shadow-cljs watch app  
shadow-cljs - config: /Users/vincent/code/nws/shadow-cljs-namespace-party/shadow-cljs.edn
shadow-cljs - starting via "clojure"
WARNING: When invoking clojure.main, use -M
shadow-cljs - HTTP server available at http://localhost:3000
shadow-cljs - server version: 2.12.5 running at http://localhost:9630
shadow-cljs - nREPL server started on port 53824
shadow-cljs - watching build :app
[:app] Configuring build.
[:app] Compiling ...
[:app] Build completed. (121 files, 0 compiled, 0 warnings, 1.81s)

This is a known limitation in CLJS and not shadow-cljs related at all.

TIL .. I did not know that limitation.

Thank you for being so reactive. 👍

[thheller]

I got the warnings on the first compile but after caching it didn't warn. Not exactly sure why but it is fixed in master.

[green-coder]

One explanation could be that the warning is non-deterministic, that somehow it depends on the source code parsing order?

There is a warning when a variable is conflicting with a namespace, is there a warning when a namespace conflicts with a variable?

[thheller]

That is possible yes. In general the namespaces and defs are layed out as nested JS objects so basically you'd have

a.b.c.d = "foo";
a.b.c = "bar";

So in this loading order the a.b.c.d is lost since the a.b.c overwrites it. If you load in different order that clash may actually work but could then break on hot-reload or so. In general the clash should be avoided to rule out strange behaviour.

[green-coder]

The following compiled form could potentially be conflict free:

a.b.c.__SLASH__.d = "foo";
a.b.__SLASH__.c = "bar";

But I guess that the solution is not as simple as it looks, and it is probably related to the CLJS compiler.

[thheller]

Yes, if I was going to rewrite how the CLJS compiler works I'd change how namespaces are organized to avoid such conflicts. It does however require rewriting the CLJS compiler a little bit and is not something I can do via shadow-cljs.