NextJS project fails to build when using Tesseract.js

[fmercille]

Tesseract.js version (version number for npm/GitHub release, or specific commit for repo)
5.0.4

Describe the bug
A NextJS app using tesseract.js will fail to build with error Cannot find module '/my-dev-folder/.next/server/app/worker-script/node/index.js'

To Reproduce
Steps to reproduce the behavior:

1. Clone the following repo which I created to illustrate this bug: https://github.com/fmercille/tesseract-js-nextjs
2. In the project folder, run yarn install to install the dependencies
3. Run yarn build to build the NextJS app
4. See error

Expected behavior
I would expect to be able to use tesseract.js in a NextJS application.

Device Version:

• OS + Version: Ubuntu 22.04.3 LTS

Additional context
The project was created using npx create-next-app@latest tesseract-js-nextjs and accepting all the default values. The file that uses tesseract.js is /src/app/api/tesseract/route.ts. It includes reading a file into a buffer, creating a worker and then recognizing the buffer, but in reality, only creating the worker is enough to make the build fail.

[fmercille]

Another simple way to reproduce the issue without having to clone a repo:

1. Create a new NextJS project with npx create-next-app@latest my-project and accept all the default values
2. cd my-project
3. yarn install
4. yarn build --> See that the build is successful
5. yarn add tesseract.js
6. Create file src/app/api/route.ts and add the following code to it:

import { createWorker } from "tesseract.js";

export async function GET(req: Request) {
  const worker = await createWorker("eng");
  return new Response();
}

7. yarn build --> See the error

[Balearica]

When I ran your repo I got a file path (Cannot find module) error. This indicates that the worker code is not being found automatically, so the path needs to be set manually. This can be done using the workerPath argument. In your case, I think this would look like the following:

const worker = await createWorker("eng", 1, {workerPath: "./node_modules/tesseract.js/src/worker-script/node/index.js"});

For context, Tesseract.js "workers" get their own web worker (browser) or worker thread (Node.js), which is independent code that uses a different entry point. When Tesseract.js is used on its own, this entrypoint should be identified automatically. However, this may not hold with build systems implemented by various frameworks, as these build systems copy around files in a way that violates Tesseract.js's assumptions for where files are located.

[fmercille]

That is actually very helpful information. It works now. Thanks a lot :-)

[meronogbai]

I encountered this issue and setting workerPath didn't help. I fixed the issue by adding tesseract.js to serverComponentsExternalPackages in my next config.