creating a build with --optimizations other than none fails

[johbra]

Creating a build with
clojure -M -m figwheel.main --optimizations none --build-once anything
all works correctly.

Trying
clojure -M -m figwheel.main --optimizations whitespace --build-once anything
I get

SLF4J: No SLF4J providers were found.
SLF4J: Defaulting to no-operation (NOP) logger implementation
SLF4J: See https://www.slf4j.org/codes.html#noProviders for further details.
[Figwheel] Compiling build anything to "target/public/cljs-out/anything-main.js"
Feb. 14, 2026 11:44:41 PM com.google.javascript.jscomp.LoggerErrorManager println
SCHWERWIEGEND: /Users/jb/tmp/anti/target/public/cljs-out/anything/goog/i18n/numberformat.js:963:8: ERROR - [JSC_LANGUAGE_FEATURE] This language feature is only supported for ECMASCRIPT_2019 mode or better: Optional catch binding.
963| } catch {
^

Feb. 14, 2026 11:44:41 PM com.google.javascript.jscomp.LoggerErrorManager println
SCHWERWIEGEND: /Users/jb/tmp/anti/target/public/cljs-out/anything/goog/i18n/numberformat.js:1011:6: ERROR - [JSC_LANGUAGE_FEATURE] This language feature is only supported for ECMASCRIPT_2019 mode or better: Optional catch binding.
1011| } catch {
^

Feb. 14, 2026 11:44:41 PM com.google.javascript.jscomp.LoggerErrorManager printSummary
WARNUNG: 2 error(s), 0 warning(s)
ERROR: JSC_LANGUAGE_FEATURE. This language feature is only supported for ECMASCRIPT_2019 mode or better: Optional catch binding. at /Users/jb/tmp/anti/target/public/cljs-out/anything/goog/i18n/numberformat.js line 963 : 8
ERROR: JSC_LANGUAGE_FEATURE. This language feature is only supported for ECMASCRIPT_2019 mode or better: Optional catch binding. at /Users/jb/tmp/anti/target/public/cljs-out/anything/goog/i18n/numberformat.js line 1011 : 6
[Figwheel] Failed to compile build anything in 4.651 seconds.
[Figwheel:WARNING] Compile Exception: Closure compilation failed
[Figwheel:SEVERE]
Unexpected error compiling at (REPL:1).
Closure compilation failed

What is going wrong

[bhauman]

The Closure Compiler bundled with your ClojureScript version defaults to a language level that doesn't support ES2019+ syntax like optional catch binding. A dependency in your project likely contains this syntax.

Two options:

1. Add :language-in :ecmascript-2019 (or higher) to your compiler options in your .cljs.edn file. We just merged PR #341 which adds support for these newer language level options in figwheel-main's config validation.

2. Upgrade your ClojureScript version — newer releases bundle an updated Closure Compiler that handles this syntax by default.

[johbra]

Thanks for the hints jb Am 17.03.2026 um 04:39 schrieb Bruce Hauman ***@***.***>: [ACHTUNG EXTERNE MAIL] Prüfen Sie den Absender! Öffnen Sie nur Anhänge oder Links aus vertrauenswürdigen Quellen! Verdachtsfälle bitte an ***@***.*** melden. Closed #353<#353> as completed. — Reply to this email directly, view it on GitHub<#353 (comment)>, or unsubscribe<https://github.com/notifications/unsubscribe-auth/AAFLXX55FLVGSQS3EELVA2T4RDCHBAVCNFSM6AAAAACVE6DDO2VHI2DSMVQWIX3LMV45UABCJFZXG5LFIV3GK3TUJZXXI2LGNFRWC5DJN5XDWMRTGYZDSMRUHE4TKOA>. You are receiving this because you authored the thread.Message ID: ***@***.***>