fix: restore src-gen frontend production behavior

[sdirix]

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, webpack 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

What it does

Use require for importing frontend modules in production mode, use import in the remaining modes (mainly development).

How to test

Trigger src-gen for the included example applications. Trigger with --mode development as well as --mode production.

Review checklist

• As an author, I have thoroughly tested my changes and carefully followed the review guidelines

Reminder for reviewers

• As a reviewer, I agree to behave in accordance with the review guidelines

Context

The require generation was removed with #12590

[msujew]

Does it make sense to replace all import statements with require? I.e. even in development build? Is there a benefit of using import at all in this context?

Note that we should definitely replace the import call at line 100.

[sdirix]

Note that we should definitely replace the import call at line 100.

Ah I missed that! Good catch! Will update the PR.

Does it make sense to replace all import statements with require? I.e. even in development build? Is there a benefit of using import at all in this context?

Good questions, I assumed that the webpack build can be a bit faster, including in watch mode, if all modules are bundled separately. However I did not check whether that's really the case.

[sdirix]

I did a quick test with require vs import in the development build and could not find an improvement there in build times nor watch times. However I don't know whether we'll break somebody's use case if we now always generate require. If it's fine for you I would like to suggest to only restore the previous behavior for now, so that the feature is unchanged for the next release and discuss this further in the dev meetings or in the forums.

[msujew]

Looks good to me 👍

Please rebase so I can merge :)