If `tsconfig.json` is set to CommonJS mode, the declaration files cannot be read.

[yuheiy]

Reproduction link

No response

Bug description

If tsconfig.json is set to CommonJS mode, the declaration files for almost modules cannot be read.

tsconfig.json:

{
  "compilerOptions": {
    "module": "CommonJS",
    "moduleResolution": "Node10",
    "strict": true
  }
}

test.ts:

The cause is probably that the types is not set in package.json.

	"main": "dist/index.cjs",
	"module": "dist/index.mjs",
+	"types": "dist/index.d.ts",
	"exports": {
		".": {
			"import": {
				"types": "./dist/index.d.ts",
				"default": "./dist/index.mjs"
			},
			"require": {
				"default": "./dist/index.cjs"
			}
		}
	},

Actual Behavior

No response

Expected Behavior

No response

Can you reproduce it with npx @csstools/csstools-cli <plugin-name> minimal-example.css?

None

npx Output

No response

Extra config

No response

What plugin are you experiencing this issue on?

No response

Plugin version

What OS are you experiencing this on?

No response

Node Version

20

Validations

• Follow our Code of Conduct
• Check that there isn't already an issue that request the same feature to avoid creating a duplicate.

Would you like to open a PR for this bug?

• I'm willing to open a PR

[romainmenke]

Hi @yuheiy,

This is not a bug, this is by design.
We do not provide types for commonjs, only for es modules.

The types we do have for es modules are only valid for the es modules source, not for the commonjs source.

See #1031 (comment) for more context.

[yuheiy]

Oh, thanks for your reply.

I found the following comment in that issue:

If however such a tool does exist, please let us know.
We are happy to change our setup to make this possible.

So, do you know about unbuild and tshy? What do you think about these?

[romainmenke]

Thank you for checking out some tools @yuheiy,

At first glance unbuild doesn't seem to solve the hard problems and only works for projects that happen to have compatible JavaScript that can be easily transpiled between commonjs and es modules (unjs/unbuild#374)

I tried tshy and it didn't work at all, I am sure it can work. It just doesn't work at all for me, for what I want it to do.
It also fails to solve the hard problems : https://github.com/isaacs/tshy?tab=readme-ov-file#handling-default-exports

---

At this time I've kinda embraced this issue. Typings are a secondary feature and es modules is the future. So from our perspective it makes more sense to focus on providing the best dev experience for es modules while also having a correct runtime for commonjs.

[yuheiy]

Thank you for your explanation. Now that I understand what the problem is, I will close the issue.

[yuheiy]

Just so you know, I initially aimed to create a CommonJS (only) package using your module with tsc, specifically a PostCSS plugin. Given the issue, I've now decided to go with a bundler instead.