[Netlify functions] TypeError on hitting function from netlify dev

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1

I deploy locally using netlify dev on netlify-cli@5.4.1 installed globally.

The (relevant) output is as follows

◈ Loaded function test.
◈ Functions server is listening on 56559
◈ Starting Netlify Dev with Create React App

However when I hit this function using postman or some other HTTP client the instance crashes with the following error

Request from ::1: GET /.netlify/functions/test
TypeError: Cannot read property 'join' of undefined
    at formatLambdaLocalError (/Users/eddyoc/.config/yarn/global/node_modules/netlify-cli/src/lib/functions/synchronous.js:36:100)
    at handleErr (/Users/eddyoc/.config/yarn/global/node_modules/netlify-cli/src/lib/functions/synchronous.js:40:55)
    at handleSynchronousFunction (/Users/eddyoc/.config/yarn/global/node_modules/netlify-cli/src/lib/functions/synchronous.js:17:12)
    at handler (/Users/eddyoc/.config/yarn/global/node_modules/netlify-cli/src/lib/functions/server.js:102:7)
    at processTicksAndRejections (internal/process/task_queues.js:95:5)
TypeError: Cannot read property 'join' of undefined
    at formatLambdaLocalError (/Users/eddyoc/.config/yarn/global/node_modules/netlify-cli/src/lib/functions/synchronous.js:36:100)
    at handleErr (/Users/eddyoc/.config/yarn/global/node_modules/netlify-cli/src/lib/functions/synchronous.js:40:55)
    at handleSynchronousFunction (/Users/eddyoc/.config/yarn/global/node_modules/netlify-cli/src/lib/functions/synchronous.js:17:12)
    at handler (/Users/eddyoc/.config/yarn/global/node_modules/netlify-cli/src/lib/functions/server.js:102:7)
    at processTicksAndRejections (internal/process/task_queues.js:95:5)

This function works fine when deployed on netlify. However it makes it impossible for me to locally run or debug my functions

2

Welcome to the forums @eddyoc

Are you able to share you code so that others may assist in determining what you are trying to join and why it is undefined?

3

The code is hello world. The error is being thrown inside netlify-cli. Note that this only happens locally, there are no errors once this is deployed.

const handler = async (event, context) => {
  return {
    statusCode: 200,
    body: JSON.stringify({ message : 'hello world' }),
  };
};

module.exports = {
  handler,
}
4

I see you opened an issue too Cannot read property 'join' of undefined · Issue #3050 · netlify/cli · GitHub. Have you tried they suggestions posted there?