Webpack Compilation Error when upgrading @jscutlery/cypress-harness to 0.8.10

[hassamahmed]

After upgrading to @jscutlery/cypress-harness v0.8.10, Webpack 5 fails to compile ESM modules due to missing .js extensions in internal imports.

Module not found: Error: Can't resolve './lib/get-root-harness' in '/agent/_work/1/s/Source/Client/node_modules/@jscutlery/cypress-harness/src'
Did you mean 'get-root-harness.js'?
BREAKING CHANGE: The request './lib/get-root-harness' failed to resolve only because it was resolved as fully specified
(probably because the origin is strict EcmaScript Module, e. g. a module with javascript mimetype, a '*.mjs' file, or a '*.js' file where the package.json contains '"type": "module"').
The extension in the request is mandatory for it to be fully specified.
Add the extension to the request.
    at handle (/agent/_work/1/s/Source/Client/node_modules/@cypress/webpack-preprocessor/dist/index.js:296:23)
    at finalCallback (/agent/_work/1/s/Source/Client/node_modules/webpack/lib/Compiler.js:519:32)
    at /agent/_work/1/s/Source/Client/node_modules/webpack/lib/Compiler.js:597:17
    at /agent/_work/1/s/Source/Client/node_modules/webpack/lib/HookWebpackError.js:96:2
    at Hook.eval [as callAsync] (eval at create (/agent/_work/1/s/Source/Client/node_modules/tapable/lib/HookCodeFactory.js:31:10), <anonymous>:6:1)
    at Hook.CALL_ASYNC_DELEGATE [as _callAsync] (/agent/_work/1/s/Source/Client/node_modules/tapable/lib/Hook.js:21:14)
    at Cache.storeBuildDependencies (/agent/_work/1/s/Source/Client/node_modules/webpack/lib/Cache.js:129:37)
    at /agent/_work/1/s/Source/Client/node_modules/webpack/lib/Compiler.js:593:19
    at Hook.eval [as callAsync] (eval at create (/agent/_work/1/s/Source/Client/node_modules/tapable/lib/HookCodeFactory.js:31:10), <anonymous>:6:1)
    at Hook.CALL_ASYNC_DELEGATE [as _callAsync] (/agent/_work/1/s/Source/Client/node_modules/tapable/lib/Hook.js:21:14)
    at /agent/_work/1/s/Source/Client/node_modules/webpack/lib/Compiler.js:589:23
    at Compiler.emitRecords (/agent/_work/1/s/Source/Client/node_modules/webpack/lib/Compiler.js:1067:4)
    at /agent/_work/1/s/Source/Client/node_modules/webpack/lib/Compiler.js:579:11
    at /agent/_work/1/s/Source/Client/node_modules/webpack/lib/Compiler.js:1030:14
    at Hook.eval [as callAsync] (eval at create (/agent/_work/1/s/Source/Client/node_modules/tapable/lib/HookCodeFactory.js:31:10), <anonymous>:6:1)
    at Hook.CALL_ASYNC_DELEGATE [as _callAsync] (/agent/_work/1/s/Source/Client/node_modules/tapable/lib/Hook.js:21:14)
    at /agent/_work/1/s/Source/Client/node_modules/webpack/lib/Compiler.js:1027:27
    at /agent/_work/1/s/Source/Client/node_modules/neo-async/async.js:2818:7
    at done (/agent/_work/1/s/Source/Client/node_modules/neo-async/async.js:3522:9)
    at Hook.eval [as callAsync] (eval at create (/agent/_work/1/s/Source/Client/node_modules/tapable/lib/HookCodeFactory.js:31:10), <anonymous>:6:1)
    at Hook.CALL_ASYNC_DELEGATE [as _callAsync] (/agent/_work/1/s/Source/Client/node_modules/tapable/lib/Hook.js:21:14)
    at /agent/_work/1/s/Source/Client/node_modules/webpack/lib/Compiler.js:856:33
    at /agent/_work/1/s/Source/Client/node_modules/graceful-fs/graceful-fs.js:143:16
    at /home/AzDevOps/.cache/Cypress/14.5.2/Cypress/resources/app/node_modules/@packages/server/node_modules/graceful-fs/graceful-fs.js:143:16
    at /home/AzDevOps/.cache/Cypress/14.5.2/Cypress/resources/app/node_modules/@packages/server/node_modules/graceful-fs/graceful-fs.js:143:16
    at /home/AzDevOps/.cache/Cypress/14.5.2/Cypress/resources/app/node_modules/@packages/server/node_modules/graceful-fs/graceful-fs.js:61:14
    at FSReqCallback.oncomplete (node:fs:186:23)

This occurred while Cypress was compiling and bundling your test code. This is usually caused by:

- A missing file or dependency
- A syntax error in the file or one of its dependencies

Fix the error in your code and re-run your tests.

Workarounds Tried:

• Setting resolve.fullySpecified = false (Angular CLI ignores custom webpack settings)
• Setting loader override:
  { test: /@jscutlery\/cypress-harness\/.*\.js$/, type: "javascript/auto" }

Resolution:

• Downgraded @jscutlery/cypress-harness to 0.7.0

Cypress Version
14.5.4

Node version
22.22.1