Sometime between Wednesday September 30th 2020 and Thursday October 1st 2020, the behavior of mocha during a clean npm install --production changed. Previously, the command resulted in no node_modules folder being created. Since, the command has consitently resulted in the creation of a node_modules folder with the following contents:

• define-properties
• es-abstract
• es-to-primitive
• function-bind
• has
• has-symbols
• is-callable
• is-date-object
• is-regex
• is-symbol
• object-inspect
• object-keys
• string.prototype.trimend
• string.prototype.trimstart

This is an important issue as AWS Lambda@Edge code packages have a size limitation of 1048576 bytes, and the automated build tooling provided by AWS SAM will include these node_modules contents, violating the service limit. The only workaround is to add a cleanup step in the build process to delete the node_modules folder after building but before publishing the package for use in Lambda@Edge.

1. git clone https://github.com/danludwig/npm-module-bug-reports.git
2. cd npm-module-bug-reports/mocha-2020-10-bug
3. Observe that the ./package.json has only a devDependency on mocha
4. npm install --production
5. Observe that a node_modules folder was created with the above listed contents.

1. cd ../mocha-2020-10-expected
2. Observe that the ./package.json has only a devDependency on chai
3. npm install --production
4. Observe that no node_modules folder was created.