fix: restore src-gen frontend production behavior

Restores the usage of 'require' in production mode when loading
included modules.

At the moment, both in development as well as in production mode, the
frontend will be generated using the 'import' function. Webpack will
use this opportunity for code splitting, leading to the generation of
many small bundles. As they are sequentially loaded, this has a
negative effect on the startup speed of the frontend.

By using 'require' instead, wepack will produce a single bundle, which
is faster to transmit without additional roundtrips. This behavior was
used for production mode in all previous Theia versions and is now
restored.

Contributed on behalf of STMicroelectronics

CHANGELOG.md

@@ -6,6 +6,7 @@
 
 ## v1.42.0
 
+- [application-package] restore src-gen frontend production behavior [12950](https://github.com/eclipse-theia/theia/pull/12950) - Contributed on behalf of STMicroelectronics
 - [core] fixed logger level propagation when log config file changes at runtime [#12566](https://github.com/eclipse-theia/theia/pull/12566) - Contributed on behalf of STMicroelectronics
 - [vscode] stub TestController invalidateTestResults [#12944](https://github.com/eclipse-theia/theia/pull/12944) - Contributed by STMicroelectronics
 - [vscode] support iconPath in QuickPickItem [#12945](https://github.com/eclipse-theia/theia/pull/12945) - Contributed by STMicroelectronics

dev-packages/application-manager/src/generator/frontend-generator.ts

@@ -125,7 +125,7 @@ module.exports = (async () => {
 
     try {
 ${Array.from(frontendModules.values(), jsModulePath => `\
-        await load(container, import('${jsModulePath}'));`).join(EOL)}
+        await load(container, ${this.options.mode !== 'production' ? 'import' : 'require'}('${jsModulePath}'));`).join(EOL)}
         await start();
     } catch (reason) {
         console.error('Failed to start the frontend application.');