[Solved] TypeError — yarn start stopped working

I’m posting this to try to help anyone who may find themselves stuck.

I am on macOS 10.14.6 / Yarn 1.22.

I started experiencing an error today — I don’t know why it started happening, all I know is several attempts to clean-wipe Node/NPM/Yarn/clone from GitHub, etc. nothing worked. I kept getting this stack trace whenever I tried to run yarn start:

TypeError [ERR_INVALID_ARG_TYPE]: The "path" argument must be of type string. Received undefined
    at validateString (internal/validators.js:118:11)
    at Object.join (path.js:1039:7)
    at noopServiceWorkerMiddleware (/Users/zaydek/github/codex-app/node_modules/react-dev-utils/noopServiceWorkerMiddleware.js:14:26)
    at Layer.handle [as handle_request] (/Users/zaydek/github/codex-app/node_modules/express/lib/router/layer.js:95:5)
    at trim_prefix (/Users/zaydek/github/codex-app/node_modules/express/lib/router/index.js:317:13)
    at /Users/zaydek/github/codex-app/node_modules/express/lib/router/index.js:284:7
    at Function.process_params (/Users/zaydek/github/codex-app/node_modules/express/lib/router/index.js:335:12)
    at next (/Users/zaydek/github/codex-app/node_modules/express/lib/router/index.js:275:10)
    at launchEditorMiddleware (/Users/zaydek/github/codex-app/node_modules/react-dev-utils/errorOverlayMiddleware.js:20:7)
    at Layer.handle [as handle_request] (/Users/zaydek/github/codex-app/node_modules/express/lib/router/layer.js:95:5)
    at trim_prefix (/Users/zaydek/github/codex-app/node_modules/express/lib/router/index.js:317:13)
    at /Users/zaydek/github/codex-app/node_modules/express/lib/router/index.js:284:7
    at Function.process_params (/Users/zaydek/github/codex-app/node_modules/express/lib/router/index.js:335:12)
    at next (/Users/zaydek/github/codex-app/node_modules/express/lib/router/index.js:275:10)
    at handleWebpackInternalMiddleware (/Users/zaydek/github/codex-app/node_modules/react-dev-utils/evalSourceMapMiddleware.js:42:7)
    at Layer.handle [as handle_request] (/Users/zaydek/github/codex-app/node_modules/express/lib/router/layer.js:95:5)

What ended up fixing it (at least for now) is updating to the latest CRA version e.g. yarn add --exact react-scripts@3.4.0.

Something react scripts was calling was breaking. Anyway, this is fixed — I hope this helps someone.

[HRussellZFAC023]

I also have this issue:

[nealeu]

I’m posting this to try to help anyone who may find themselves stuck.

@codex-zaydek Thank you for being so thoughtful. You certainly helped me, and I’m glad to say that it’s something I try to remember to do when I find an answer no one else seems to have done.