maintaining-cjs-module-lexer.md

Maintaining cjs-module-lexer

The cjs-module-lexer dependency is used within the Node.js ESM implementation to detect the named exports of a CommonJS module.

It is used within node:internal/modules/esm/translators in which both internal/deps/cjs-module-lexer/lexer and internal/deps/cjs-module-lexer/dist/lexer are required and used.

internal/deps/cjs-module-lexer/lexer is a regular JavaScript implementation that is used when WebAssembly is not available on a platform. internal/deps/cjs-module-lexer/dist/lexer is a faster implementation using WebAssembly which is generated from a C based implementation. These two paths resolve to the files in deps/cjs-module-lexer due to their inclusion in the deps_files entry in node.gyp.

The two different versions of lexer.js are maintained in the nodejs/cjs-module-lexer project.

In order to update the Node.js dependencies to use to a newer version of cjs-module-lexer, complete the following steps:

• Clone nodejs/cjs-module-lexer and check out the version that you want Node.js to use.
• Follow the WASM build steps outlined in wasm-build-steps. This will generate the WASM based dist/lexer.js file.
• Preserving the same directory structure, copy the following files over to deps/cjs-module-lexer directory where you have checked out Node.js.

├── CHANGELOG.md
├── dist
│   ├── lexer.js
│   └── lexer.mjs
├── lexer.js
├── LICENSE
├── package.json
└── README.md

• Update the link to the cjs-module-lexer in the list at the end of doc/api/esm.md to point to the updated version.

• Create a PR, adding the files in the deps/cjs-module-lexer that were modified.

If updates are needed to cjs-module-lexer for Node.js, first PR those updates into nodejs/cjs-module-lexer, request a release and then pull in the updated version once available.