Make Theia webpack-based bundle packaging customizable

[davidfestal]

Currently, the Theia webpack configuration file, as well as the main HTML file that loads the packaged JS bundle file, are generated during Theia build.

In order to provide enable bundle caching in a way that can be customized by the theia distributrion packager, we should introduce a way to customize:

• the webpack configuration, at least providing an option to enable a typical caching-compatible configuration (see https://webpack.js.org/guides/caching/)
• the generated HTML using the HtmlWebpackPlugin, in order to let the user provide its own template during the theia build call, as well as additional html template parameters through command line arguments.

The result of this work should be to have the related PR merged in the upstream Theia repository.

[davidfestal]

The following PR has been opened in the Theia repository: eclipse-theia/theia#3522

[davidfestal]

Let me comment about the current status of tth issue:

Finally fhe work done on CDNs on che-theia (see branch https://github.com/eclipse/che/compare/theia-cdn-support) was done without requiring any change in Theia upstream, by using:

1. a custom Webpack configuration that imports the default generated Theia webpack configuration and introduces CDN-related optimizations / changes
2. a custom HTML template used in the custom webpack configuration. For now this custom HTML template duplicates a bit the content of the default theia generated HTML,
3. a custom JS file overrides the vs/loader.js monaco requireJS loader, in order to override the requireJS configuration.

Through it currently works well, I propose to keep this issue opened to track what parts of this work we would be able to propose in Theia upstream, or what change in Theia upstream would make our CDN work cleaner / easier to maintain, especially for the HTML template part (to avoid future syncs of duplicated code) and the vsCode requireJS overriding, which requires renaming files in the generated webpack package.

However, I think we can decrease the priority of this issue, and possibly wait for the CDN support to be used a while, and finalized. When it has reached its final shape, this issue will come back.

@ibuziuk @benoitf do you agree ?

[ibuziuk]

I agree, let's postpone it in favour of #1119

[ibuziuk]

Closing as outdated