Copy-webpack yarn theia build

Coming back to theia project. This can be very simple thing.
I am trying to build it. Got stuck on nodejs version so I moved to v12 from v16.
Now I am stuck on command yarn theia build

message is:
Failed to load … config
Invalid options object. Copy Plugin has been initialized using an options object that does not match the API schema

  • options.patterns should be a non empty array

So it is something to do with copy-webpack plugin. What should I tweek about my environment?

Hi @tsadigov! This might be unrelated to your problem, but in the Theia readme it’s suggested that you might encounter some issues with Node 16.
Did you try running yarn --ignore-engines or downgrading to Node 14, if possible?


Hard to say with the little context in your post, but my guess is that your generated gen-webpack.config.js code is out of date and needs to be regenerated.

Here’s what to expect, roughly (L27-L38):

const plugins = [
    new CopyWebpackPlugin({
        patterns: [{
            from: monacoEditorCorePath,
            to: 'vs'
    new webpack.ProvidePlugin({
        // the Buffer class doesn't exist in the browser but some dependencies rely on it
        Buffer: ['buffer', 'Buffer']

thanks, in order to avoid surprises I uninstalled 16 and instsalled nodejs12. And I get this error with v12

Hi @tsadigov,

I think this is the same issue as here. You need to add the @theia/monaco dependency to your build. Not only does Theia not build without it, even if you were to get it to build, it does not run correctly.

Hello thanks for your replies

It was my fault of misunderstanding documentation. Sorry for not being able to provide good context.

I downloaded source and checked readme for quick way to execute it to start playing with ide. Got to this link and tried to execute them inside the repo with code.
I applied commands in wrong context.

I should have looked into this link
And should have run this command
&& yarn download:plugins
&& yarn browser build
&& yarn browser start

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