Exception: Cannot set property message of [object Object] which has only a getter

[wojtekmaj]

When attempting to run a function, which crashed on startup (for an unrelated reason), I got the following error:

[2023-12-12T12:41:34.171Z] Worker failed to load function: 'func-name' with functionId: '…'.
[2023-12-12T12:41:34.171Z] Result: Failure
[2023-12-12T12:41:34.171Z] Exception: Cannot set property message of [object Object] which has only a getter
[2023-12-12T12:41:34.171Z] Stack: TypeError: Cannot set property message of [object Object] which has only a getter
[2023-12-12T12:41:34.171Z]     at h.<anonymous> (/opt/homebrew/Cellar/azure-functions-core-tools@4/4.0.5455/workers/node/dist/src/worker-bundle.js:2:33509)
[2023-12-12T12:41:34.171Z]     at Generator.throw (<anonymous>)
[2023-12-12T12:41:34.171Z]     at a (/opt/homebrew/Cellar/azure-functions-core-tools@4/4.0.5455/workers/node/dist/src/worker-bundle.js:2:32342).

instead of the actual error message that got thrown by my function.

worker-bundle.js:2:33509 corresponds to this line:

t.message=`Worker was unable to load function ${r.name}: '${t.message}'`

so there's something wrong with the way errors are handled.

[ejizba]

Hi @wojtekmaj can you share your version of core tools and the "@azure/functions" npm package? If you have sample repro code, that would also be very helpful

[wojtekmaj]

@ejizba @azure/functions was at 3.5.1 in the project I could reproduce that in. I don't think that's relevant though. I can now see that what was thrown from my function was not Error, but ZodError from zod schema validation library. I believe ensureErrorType helper does not account for this. When "pure" Error is thrown the issue cannot be reproduced.

[ejizba]

Okay I think I understand what's happening here. The ZodError type apparently makes the "message" property read-only and doesn't let us change the message. We'll look into this. If you need a workaround in the meantime, you could probably catch the error yourself and either log it or convert it to a more normal error type that we can handle

[castrodd]

I have just merged two PRs that should resolve this issue: Azure/azure-functions-nodejs-worker#732 and #220.

When these changes are deployed, I will close out this issue.

[sladkoff]

@castrodd Is the fix available on Azure yet? We are experiencing a similar problem and I'm not able to find any information on the currently deployed function-host versions.