Prevent defaultServeStatic overwrite when serving custom plugin folder to load built-In plugins after deploying the browser-app lib folder on server.

[PragyanandGithub]

Hi everyone,

I'm working on a Theia-based application and want to serve plugins from a custom /plugins folder. Everything works fine on localhost, but once I deploy the lib folder to a server, loading from /plugins no longer works.

To make it work, I temporarily modified the defaultServeStatic() function in:
browser-app/lib/backend/main.js
Like this:

function defaultServeStatic(app) {
app.use(express.static(path.resolve(__dirname, '../../lib/frontend')));
// ✅ Serve the plugins directory explicitly
app.use('/plugins', express.static(path.resolve(__dirname, '../../lib/plugins')));
}
This solves the issue — but as expected, this file gets overwritten every time I rebuild the app, and I lose the changes.

❓ My question:
What is the correct way to persist this app.use('/plugins', ...) logic, so it survives rebuilds and works both locally and in production?

I've already tried adding a server.ts file under src/backend and setting "main": "lib/backend/server.js" in package.json, but I’m not sure if that fully overrides the default backend behavior or if something else is still calling defaultServeStatic() from main.js.

Any guidance on the proper way to customize and persist backend static routes in Theia would be greatly appreciated!

Thanks in advance!

[msujew]

Hey @PragyanandGithub,

You can create a new BackendApplicationContribution and override the configure(app: Application) method to register any Express endpoint you want.

theia/packages/core/src/node/backend-application.ts

Lines 78 to 90 in 11d0c9e

	/**
	* Called after the initialization of the backend application is complete.
	* Use this to configure the Express app before it is started, for example
	* to offer additional endpoints.
	*
	* The implementation may be async, however it will still block the
	* configuration step until it's resolved.
	*
	* @param app the express application to configure.
	*
	* @returns either `undefined` or a Promise resolving to `undefined`.
	*/
	configure?(app: express.Application): MaybePromise<void>;

[PragyanandGithub]

@msujew Thanks for your support !!
It is working now after ruuning the command set THEIA_DEFAULT_PLUGINS=local-dir:D:\Workspace_CodeEditor\CodeEditorModule\browser-app\lib\plugins node main.js --hostname 0.0.0.0

Is there any way to set manually THEIA_DEFAULT_PLUGINS=local-dir:D:\Workspace_CodeEditor\CodeEditorModule\browser-app\lib\plugins ?

[msujew]

I would recommend using the --plugins argument instead. See also:

theia/examples/browser/package.json

Line 102 in b1e0469

"start": "theia start --plugins=local-dir:../../plugins --ovsx-router-config=../ovsx-router-config.json",

[PragyanandGithub]

@msujew I'm using "start": "theia start --plugins=local-dir:../plugins", in my browser-app package.json but I don't think it will work when I will start the server using node main.js . I'm not sure ..but will check for sure.

[msujew]

You can just use node main.js --plugins=local-dir:../plugins just as well. The arguments from theia start are directly passed to the server file as is.

[PragyanandGithub]

@msujew Thank you! I really appreciate your support and quick response. That clarified a lot for me. 🙌