Browser-only static extension support

[robertjndw]

What it does

This PR introduces support for static extension/plugin declaration in the Browser-Only mode. The required plugins can either be download and added manually to the respective directory or automatically through the theiaPlugins property. I've added a script which automatically unpacks the .vsix files in the theiaPluginsDir property and bundles them with the browser-only variant of Theia.
Currently, the metadata have to be specified by hand afterwards and will be injected at startup. An example of this can be found the in the respective directory.
Details on how to specify and craft those metadata are described in the file ADOPTING.md

How to test

As an example, I have chosen the Typescript Language tools as they run smoothly and represent a real world use case:

1. Head to the browser-only example and run npm run download:plugins
2. Change the corresponding paths in example-static-plugin-metadata.ts to the respective path on your system. Currently, it assumes /home/user/theia as path, just replace this part with your local theia location
3. Run the npm run build command to build and package the plugins with the browser-only version
4. Start the application with npm run start
5. Head over to localhost:3000
6. Verify that the plugins are installed (under the extensions tab, they should be listed as builtin)
7. Create a Typescript file and while coding the autocompletion and syntax highlighting should work

Follow-ups

Unfortunately, there are some limitation which can/should be tackled in future work

• The metadata configuration is currently done by hand. There are some methods in the node directory which would come in handy in automatic this. These should be outsourced into a independent package for handling Extension package.json files in both the node and browser-only variant
• There is no dynamic installation of plugins. They have to be configured and bundled with Theia. In future work, there might be an option to install plugins at runtime from the OpenVSX registry.
• Some VScode Web Extensions do not work. It seems that it has to do with the way they are bundled. An error message like module is undefined occurs when the plugin is executed and it happens in statements like module.export = i. This is strange as module is typically a Node.js thing. However, the general installation and bundling works and the error occurs directly in the plugin's bundled code when executed. To be investigated further ...

Breaking changes

• This PR introduces breaking changes and requires careful review. If yes, the breaking changes section in the changelog has been updated.

Attribution

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

[sdirix]

Thanks for the contribution!

Sadly I was not able to get the TS plugin working on my machine. It seems that some plugin storage directory was not creatable in opfs.

failed to load plugins: Unknown (FileSystemError): Error while accessing resource file:///globalStorage
    at createFileSystemProviderError (http://localhost:3000/bundle.js:381479:27)
    at OPFSFileSystemProvider.stat (http://localhost:3000/packages_filesystem_lib_browser-only_browser-only-filesystem-frontend-module_js.js:235:61)
    at async FileService.mkdirp (http://localhost:3000/bundle.js:378429:30)
    at async FileService.createFolder (http://localhost:3000/bundle.js:378413:9)
    at async HostedPluginSupport.getHostGlobalStoragePath (http://localhost:3000/packages_plugin-ext_lib_hosted_browser_hosted-plugin_js.js:732:13)
    at async Promise.all (index 2)
    at async HostedPluginSupport.startPlugins (http://localhost:3000/packages_plugin-ext_lib_hosted_browser_hosted-plugin_js.js:1401:71)
    at async HostedPluginSupport.doLoad (http://localhost:3000/packages_plugin-ext_lib_hosted_browser_hosted-plugin_js.js:1265:9)
    at async ProgressService.withProgress (http://localhost:3000/bundle.js:357799:20)
    at async http://localhost:3000/packages_plugin-ext_lib_hosted_browser_hosted-plugin_js.js:1214:17

[sdirix]

What do you mean with "Deprecated"?

[robertjndw]

According to /theia/packages/plugin-ext/src/common/plugin-protocol.ts:573 this property is deprecated but in /theia/packages/plugin-ext/src/common/plugin-protocol.ts:60 it is not 🤔