pdfjs-dist npm update from 2.0.489 to 2.0.943 causes webpack error: Can't resolve 'babel-runtime/regenerator'

[Jaans]

After updating our npm package for pdfjs-dist from 2.0.489 to 2.0.943, webpack fails to build.
If we downgrade back to version 2.0.489 all is well again and the errors go away.

Here's a copy of the webpack build log showing the failures:

 10% building 1/1 modules 0 activei ｢wds｣: Project is running at http://localhost:8081/
i ｢wds｣: webpack output is served from /
i ｢wds｣: Content not from webpack is served from C:\xxxxxx\Website\dist                                                                                                                                                                                                                                                                                                                                                         × ｢wdm｣:    2471 modules
ERROR in ./node_modules/pdfjs-dist/lib/core/pdf_manager.js
Module not found: Error: Can't resolve 'babel-runtime/regenerator' in 'C:\xxxxxx\Website\node_modules\pdfjs-dist\lib\core'

ERROR in ./node_modules/pdfjs-dist/lib/core/evaluator.js
Module not found: Error: Can't resolve 'babel-runtime/regenerator' in 'C:\xxxxxx\Website\node_modules\pdfjs-dist\lib\core'

ERROR in ./node_modules/pdfjs-dist/lib/core/obj.js
Module not found: Error: Can't resolve 'babel-runtime/regenerator' in 'C:\xxxxxx\Website\node_modules\pdfjs-dist\lib\core'

ERROR in ./node_modules/pdfjs-dist/lib/display/fetch_stream.js
Module not found: Error: Can't resolve 'babel-runtime/regenerator' in 'C:\xxxxxx\Website\node_modules\pdfjs-dist\lib\display'

ERROR in ./node_modules/pdfjs-dist/lib/display/network.js
Module not found: Error: Can't resolve 'babel-runtime/regenerator' in 'C:\xxxxxx\Website\node_modules\pdfjs-dist\lib\display'

ERROR in ./node_modules/pdfjs-dist/lib/display/node_stream.js
Module not found: Error: Can't resolve 'babel-runtime/regenerator' in 'C:\xxxxxx\Website\node_modules\pdfjs-dist\lib\display'

ERROR in ./node_modules/pdfjs-dist/lib/display/transport_stream.js
Module not found: Error: Can't resolve 'babel-runtime/regenerator' in 'C:\xxxxxx\Website\node_modules\pdfjs-dist\lib\display'

ERROR in ./node_modules/pdfjs-dist/lib/shared/message_handler.js
Module not found: Error: Can't resolve 'babel-runtime/regenerator' in 'C:\xxxxxx\Website\node_modules\pdfjs-dist\lib\shared'

ERROR in ./node_modules/pdfjs-dist/lib/web/ui_utils.js
Module not found: Error: Can't resolve 'babel-runtime/regenerator' in 'C:\xxxxxx\Website\node_modules\pdfjs-dist\lib\web'
i ｢wdm｣: Failed to compile.

Configuration:

• Chrome: latest
• Windows 10 Professional: Latest updates
• PDF.js version: 2.0.943
• Is a browser extension: No

What is the expected behavior? (add screenshot)
For the webpack build to succeed.

What went wrong? (add screenshot)
The webpack build fails, citing errors in the pdfjs-dist npm package for:
Module not found: Error: Can't resolve 'babel-runtime/regenerator'

Package.json excerpt follows:

{
 ...
 "engines": {
    "node": ">= 8.9.0"
  },
  "private": true,
  "devDependencies": {
    "@babel/core": "^7.1.6",
    "@babel/plugin-proposal-class-properties": "^7.1.0",
    "@babel/plugin-syntax-dynamic-import": "^7.0.0",
    "@babel/preset-env": "^7.1.6",
    "babel-eslint": "^10.0.1",
    "babel-loader": "^8.0.4",
    "clean-webpack-plugin": "^1.0.0",
    "copy-webpack-plugin": "^4.6.0",
    "css-loader": "^1.0.1",
    "eslint": "^5.9.0",
    "file-loader": "^2.0.0",
    "html-loader": "^0.5.5",
    "html-webpack-plugin": "^3.2.0",
    "http-server": "^0.11.1",
    "less": "^3.8.1",
    "less-loader": "^4.1.0",
    "mini-css-extract-plugin": "^0.4.4",
    "optimize-css-assets-webpack-plugin": "^5.0.1",
    "style-loader": "^0.23.1",
    "webpack": "^4.26.0",
    "webpack-cli": "^3.1.2",
    "webpack-dev-server": "^3.1.10"
  },
  "dependencies": {
    "@babel/polyfill": "^7.0.0",
    "bootstrap": "^3.3.7",
    "font-awesome": "^4.7.0",
    "jquery": "^3.3.1",
    "jquery-ui": "^1.12.1",
    "moment": "^2.22.2",
    "pdfjs-dist": "^2.0.943",
    "popper.js": "^1.14.5",
    "uuid": "^3.3.2",
    "whatwg-fetch": "^3.0.0"
  }
}

[Jaans]

Coincidentally, version 2.0.550 works fine and does not give webpack build errors.

[timvandermeij]

I think this is because babel-runtime/regenerator is necessary for supporting the async/await syntax with Babel; refer to 099ed08#diff-b9e12334e9eafd8341a6107dd98510c9R185. It looks like the problem is that we require Babel 6 (refer to https://github.com/mozilla/pdf.js/blob/master/package.json#L7) whereas in your package.json you're requiring Babel 7, which may lead to a conflict. This could perhaps be resolved by us upgrading to Babel 7, but that is already tracked in #10229 for a different reason, so we can close this.

[wojtekmaj]

@timvandermeij Babel 6 or 7, doesn't really matter. If your code requires something, it should have it listed as a dependency. As such, I consider all currently released versions as faulty in that matter, and I suggest to add @babel/runtime as a dependency of pdfjs-dist. Another idea is to get rid of @babel/runtime dependency (probably the best approach).
May you consider reopening this?

[Snuffleupagus]

None of this will be a problem if you actually use the pre-built library; please see the files distributed in https://github.com/mozilla/pdfjs-dist/tree/master/build respectively in https://github.com/mozilla/pdfjs-dist/tree/master/web, which are officially supported and won't suffer from the issues described here.

[wojtekmaj]

Ah, I see. I was importing PDFLinkService which does not belong to the main lib. Thanks a bunch!

[Jaans]

I'm a little confused. The versions at https://github.com/mozilla/pdfjs-dist/tree/master/build and https://github.com/mozilla/pdfjs-dist/tree/master/web are still version 2.0.489 at the time of this writing and this version is devoid from the issue I was reporting here.

Assuming @Snuffleupagus means that we should be using the pdfjs-dist version over pdfjs then I'm confused even more because the npm package for pdfjs-dist is at version 2.0.943 which has the issue (see https://www.npmjs.com/package/pdfjs-dist)

We are needing to pin the pdfjs-dist npm package at "2.0.550" as anything more recent breaks.

Am I missing something?

[Snuffleupagus]

The versions at https://github.com/mozilla/pdfjs-dist/tree/master/build and https://github.com/mozilla/pdfjs-dist/tree/master/web are still version 2.0.489 at the time of this writing and this version is devoid from the issue I was reporting here.

See https://github.com/mozilla/pdfjs-dist/releases for the latest version, the other problem described here (non-updating master branch) is being tracked in issue #10391.

Assuming @Snuffleupagus means that we should be using the pdfjs-dist version over pdfjs

That's not what #10280 (comment) implies; rather it just points out that if you are using https://github.com/mozilla/pdfjs-dist, then you should (in general) use the files found in the build and web folders (and not the ones in the lib folder).

[Jaans]

That actually helps. Thanks for clearing up.