Warn when package.json contains an invalid "type" value

[velle]

What is the problem this feature will solve?

Valid (meaningful) values are:

• commonjs
• module

I had set CommonJS, and it behaves the same as if type was unset, which is so close to the actual commonjs behavior, that I thought I had set it correctly. But I kept having cases resulting in the MODULE_TYPELESS_PACKAGE_JSON warning, instead of failing hard.

Note that while tsconfig.js ignores case, the canonical version is CommonJS, so I never considered that I was using incorrect case.

What is the feature you are proposing to solve the problem?

Raise warning/error if "type" is set, but value is none of commonjs or module.

What alternatives have you considered?

No response

[Shuklax]

Hi @velle, I’d like to work on this. Could you point me to where the type field in package.json is currently validated/parsed in the Node.js codebase? I’d be happy to add the warning + tests.

[velle]

Great :)

I would think the check belongs in BindingData:ReadPackageJSON.

Docs for type setting: https://nodejs.org/api/packages.html#type. The text is not quite correct. When type is unset (or an invalid value) the behavior is actually different from when its set to commonjs.

• If type = 'commonjs': Processes as CJS, if fail then abort
• If type = 'module': Processes as ESM, if fail then abort
• If type is unset or other value: attempts with commonjs, and if that fails, falls back to module/ESM. And prints warning MODULE_TYPELESS_PACKAGE_JSON.

Also, I think the typescript compiler also reads package.json and looks for "type", but I don't know if it has its own check.

[abdulfarid-dev]

/assign