Issues with Google Closure Compiler and modern JavaScript

1 update

Changes by Ralf on 19/Jan/26 16:53

Description:

It seems that XWiki uses the Google Closure Compiler to minify JavaScript.

Also, it seems that Google Closure Compiler does not support modern JavaScript syntax completely (please have a look on the "no"s at the bottom of this page: [Link|https://github.com/google/closure-compiler/wiki/Supported-features]).

At least, if I use a JavaScript class with private member (=> "private" means, the name of the member starts with "#"), the Google Closure Compiler seems to have problems with that and logs error messages like the following (here the privat member was called #getLocale):
{code:java}
2025-07-14 05:39:44,591 [qtp107456312-42 - http://localhost:8080/xwiki/bin/jsx/xwiki-tools/WebHome?language=en&docVersion=59.4] ERROR c.x.x.w.s.JsExtension          - Error at line [50], column [11]: [Parse error. 'identifier' expected]
Jul 14, 2025 5:40:15 AM com.google.javascript.jscomp.LoggerErrorManager println
SEVERE: xwiki:xwiki-tools.WebHome:50:11: ERROR - [JSC_PARSE_ERROR] Parse error. 'identifier' expected
  50|       this.#getLocale = getLocale;
                 ^

Jul 14, 2025 5:40:15 AM com.google.javascript.jscomp.LoggerErrorManager printSummary
WARNING: 1 error(s), 0 warning(s) {code}
If my interpretations are wrong, please let me know.
Otherwise, is there anything I can do against those errors (except for refraining from using modern JavaScript features)?

Maybe, a solution could be that XWiki will use some other tool to minify JavaScript (for example "terser" or whatever).

Thank you very much.

[Edit] Tested with XWiki v17. 0. 5 .0 , v16.10.8 and v15.10.16 - everywhere there's this issue.

1 comment

	Ralf on 19/Jan/26 16:53

	Hello [~tmortagne], I've tested with XWiki v17. 0. 5 .0 , v16.10.8 and v15.10.16 - everywhere I got these Goolge Closure Compiler issues. To reproduce: Open a XWiki page of your choice and add the following JavaScript snippet as JavaScriptExtension (Configuration"Use this extension" => "On this page or on demand", "Caching policy" => "Long"): {code:java} class Demo { #greeting = 'Hello!'; sayHello() { alert(this.#greeting); } } new Demo().sayHello(); {code} Now "Save & View" the page. In the logs you'll find error messages like the following: {{-------------}} {{XWiki v17.5.0}} {{-------------}} {{SEVERE: xwiki:Main.WebHome:2:2: ERROR - [JSC_PARSE_ERROR] Parse error. '}' expected}} {{ 2\| #greeting = 'Hello!';}} {{ ^}} {{Jul 24, 2025 3:42:14 PM com.google.javascript.jscomp.LoggerErrorManager printSummary}} {{WARNING: 1 error(s), 0 warning(s)}} {{2025-07-24 15:42:14,934 [qtp107456312-38 - http://localhost:8080/xwiki/bin/jsx/Main/WebHome?language=en&docVersion=5.1] ERROR c.x.x.w.s.JsExtension - Error at line [2], column [2]: [Parse error. '}' expected]}} {{--------------}} {{XWiki v16.10.8}} {{--------------}} {{Jul 24, 2025 3:35:29 PM com.google.javascript.jscomp.LoggerErrorManager println}} {{SEVERE: xwiki:Main.WebHome:2:2: ERROR - [JSC_PARSE_ERROR] Parse error. '}' expected}} {{ 2\| #greeting = 'Hello!';}} {{ ^}} {{Jul 24, 2025 3:35:29 PM com.google.javascript.jscomp.LoggerErrorManager printSummary}} {{WARNING: 1 error(s), 0 warning(s)}} {{2025-07-24 15:35:29,983 [qtp1627428162-161 - http://localhost:8080/xwiki/bin/jsx/Main/WebHome?language=de&docVersion=6.1] ERROR c.x.x.w.s.JsExtension - Error at line [2], column [2]: [Parse error. '}' expected]}} {{---------------}} {{XWiki v15.10.16}} {{---------------}} {{SEVERE: xwiki:Main.WebHome:2:2: ERROR - [JSC_PARSE_ERROR] Parse error. '}' expected}} {{ 2\| #greeting = 'Hello!';}} {{ ^}} {{Jul 24, 2025 3:39:34 PM com.google.javascript.jscomp.LoggerErrorManager printSummary}} {{WARNING: 1 error(s), 0 warning(s)}} {{2025-07-24 15:39:34,232 [qtp1682463303-150 - http://localhost:8080/xwiki/bin/jsx/Main/WebHome?language=en&docVersion=75.1] ERROR c.x.x.w.s.JsExtension - Error at line [2], column [2]: [Parse error. '}' expected]}}

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