aws-lambda-nodejs deploy fails: Uploaded file must be a non-empty zip

TL;DR

Delete the asset file for that function from the bootstrap S3 bucket and redeploy, which forces CDK to re-upload a fresh zip; a maintainer suggested exactly this. The dependencies had just been updated, and a nearly identical API and Lambda in the same project deployed fine.

Steps

1. Deploying a Lambda with the aws-lambda-nodejs NodejsFunction construct failed with Uploaded file must be a non-empty zip. The dependencies had just been updated, and a nearly identical API and Lambda in the same project deployed fine. The cause was a stale or empty asset zip that had landed in the CDK bootstrap S3 bucket, so CloudFormation received an empty package for that one function.
2. An empty zip for the asset got cached in the CDK bootstrap bucket. Delete the asset file for that function from the bootstrap S3 bucket and redeploy, which forces CDK to re-upload a fresh zip; a maintainer suggested exactly this. Several reporters also fixed it by removing the cdk.out directory and redeploying from scratch, which clears the stale local asset. Both workarounds were confirmed by multiple people in the thread.

When to use

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When not to use

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Versions

No specific versions are mentioned in the source material, so treat the fix as generally applicable and check the examples against whatever you have installed.

Why this happens

The original report does not dig into a root cause. It documents the symptom and the fix that resolved it.

In the thread https://vectle.com/threads/thr_k2XyngZuYFGInc5Ziug8RA, the question was: Deploying a Lambda with the aws-lambda-nodejs NodejsFunction construct failed with Uploaded file must be a non-empty zip. The dependencies had just been updated, and a nearly identical API and Lambda in the same project deployed fine. The cause was a stale or empty asset zip that had landed in the CDK bootstrap S3 bucket, so CloudFormation received an empty package for that one function. The verified resolution was: An empty zip for the asset got cached in the CDK bootstrap bucket. Delete the asset file for that function from the bootstrap S3 bucket and redeploy, which forces CDK to re-upload a fresh zip; a maintainer suggested exactly this. Several reporters also fixed it by removing the cdk.out directory and redeploying from scratch, which clears the stale local asset. Both workarounds were confirmed by multiple people in the thread.