bug: viem 1.15.5 and above (isows) breaks jest

[mlenser]

Is there an existing issue for this?

• I have searched the existing issues

Package Version

1.15.5

Current Behavior

Hi, since viem switched to isows as part of 1.15.5 jest is unable to handle anything inside viem.

This is likely an upstream issue that needs to be solved in isows.

Error:

 Test suite failed to run
                                                                                                                                                                               
    Jest encountered an unexpected token                                                                                                                                       
                                                                                                                                                                               
    Jest failed to parse a file. This happens e.g. when your code or its dependencies use non-standard JavaScript syntax, or when Jest is not configured to support such syntax.                                                                                                                                                                              
                                                                                                                                                                               
    Out of the box Jest supports Babel, which will be used to transform your files into valid JS based on your Babel configuration.                                            
                                                                                                                                                                               
    By default "node_modules" folder is ignored by transformers.                                                                                                               
                                                                                                                                                                               
    Here's what you can do:                                                                                                                                                    
     • If you are trying to use ECMAScript Modules, see https://jestjs.io/docs/ecmascript-modules for how to enable it.                                                        
     • If you are trying to use TypeScript, see https://jestjs.io/docs/getting-started#using-typescript                                                                        
     • To have some of your "node_modules" files transformed, you can specify a custom "transformIgnorePatterns" in your config.                                               
     • If you need a custom transformation specify a "transform" option in your config.                                                                                        
     • If you simply want to mock your non-JS modules (e.g. binary assets) you can stub them out with the "moduleNameMapper" config option.

    You'll find more details and examples of these config options in the docs:
    https://jestjs.io/docs/configuration
    For information about custom transformations, see:
    https://jestjs.io/docs/code-transformation

    Details:

    REPO_PATH\node_modules\isows\_esm\native.js:1
    ({"Object.<anonymous>":function(module,exports,require,__dirname,__filename,jest){import { getNativeWebSocket } from "./utils.js";

We're running jest the recommended way by NextJS which does not transform node_modules.

If I add the following to my jest.config.mjs it works:

const config = {
  // other config
  moduleNameMapper: {
    isows: '<rootDir>/node_modules/isows/_cjs/index.js',
  },
  transformIgnorePatterns: ['node_modules/(?!isows/)'],
};

Expected Behavior

Jest is able to use viem utils as part of the components it tests.

Steps To Reproduce

A reproduction would be a bit time consuming to set up. If desired, I can do so.

Link to Minimal Reproducible Example (StackBlitz, CodeSandbox, GitHub repo etc.)

No response

Anything else?

No response

[jxom]

Jest has pretty poor support for CJS + ESM interop at the moment. I think they have plans to make this better. I'd consider your workaround fine.

I'd highly recommend a migration to Vitest though. It's relatively straight forward, and worth it.

[katspaugh]

For anyone in the same boat, you can bypass this by mocking the isows module.
Disregard that, see the workaround in the issue description.

[mlenser]

You don't need to mock it. The provided jest.config.mjs in the issue fixes the issue while using isows from node_modules.

[github-actions]

This issue has been locked since it has been closed for more than 14 days.

If you found a concrete bug or regression related to it, please open a new bug report with a reproduction against the latest Viem version. If you have any questions or comments you can create a new discussion thread.