feat: add TypeScript related extensions support #85

JounQin · 2025-07-08T04:43:39Z

Initial checklist

I read the support docs
I read the contributing guide
I agree to follow the code of conduct
I searched issues and discussions and couldn’t find anything or linked relevant results below
I made sure the docs are up to date
I included tests (or that’s not needed)

Description of changes

close #84

Note

It only works on Node 24+ for now: nodejs/node#57756 (comment)

close #84 Signed-off-by: JounQin <[email protected]>

codecov · 2025-07-08T04:43:48Z

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (6f35eae) to head (d740285).

Additional details and impacted files

@@            Coverage Diff            @@
##              main       #85   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           23        23           
  Lines         3214      3217    +3     
=========================================
+ Hits          3214      3217    +3

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Copilot

Pull Request Overview

Adds support for TypeScript-based configuration files by recognizing .cts, .mts, and .ts extensions in the loader lookup.

Introduces .cts, .mts, and .ts keys in the loaders map to route TS files through loadScriptOrModule.

Comments suppressed due to low confidence (2)

lib/configuration.js:102

Consider updating the README or configuration documentation to mention support for .cts, .mts, and .ts files so users know these extensions are now recognized.

  '.cts': loadScriptOrModule,

lib/configuration.js:102

Add or update tests to cover loading of .cts, .mts, and .ts configuration files, ensuring the new extensions are properly recognized in practice.

  '.cts': loadScriptOrModule,

github-actions · 2025-07-08T04:44:11Z

Hi team! I don’t know what’s up as there’s no phase label. Please add one so I know where it’s at.

Thanks,
— bb

remcohaszing · 2025-07-10T12:25:48Z

I like it, but this needs to be documented.

JounQin · 2025-07-10T15:10:52Z

I like it, but this needs to be documented.

I thought it would only work with custom rcPath, but after reading the source codes https://github.com/unifiedjs/unified-engine/blob/main/lib/configuration.js#L161-L169, it actually would also work for rcName, I'll add the related document tomorrow.

wooorm · 2025-07-10T16:40:58Z

rcPath is a full path, so people should be using .ts explicitly in those cases.
This would be rcName, which is a filename, for which extensions are inferred.

What should happen if both .ts and .js are found? That’s kinda typical for TS right, to build files.

What happens in older Node, when this finds .ts but cannot parse it?

Is this really worth 3 extra stats per folder above each file? That affects everyone.

wooorm · 2025-07-10T16:41:41Z

lib/configuration.js

  '.js': loadScriptOrModule,
+  '.cts': loadScriptOrModule,
+  '.mts': loadScriptOrModule,
+  '.ts': loadScriptOrModule,


Should this not come before .js? Or is it intentional that built JS is preferred over TS

Next to docs, tests are missing

Personally I think js configs should be preferred because they're supported natively and this is just old behavior, what means if a user have a .remarkrc.ts compiled into .remarkrx.js manually, this will continue work even on unsupported Node versions.

good point, probably!

JounQin · 2025-07-10T16:45:41Z

rcPath is a full path, so people should be using .ts explicitly in those cases.

rcPath is also loaded via these loaders, so it's same here.

What happens in older Node, when this finds .ts but cannot parse it?

It throws different errors compared with current behavior: parse TypeScript as json, and aftet this PR: parse as JavaScript failed.

wooorm · 2025-07-18T16:42:14Z

okay I’m up for this, if there are docs and tests. Looks like Remco is too. @ChristianMurphy?

ChristianMurphy

Looks good to me!

remcohaszing · 2025-07-19T09:44:00Z

Considering the number of fs calls, can node --strip-types actually handle .cts? I have my doubts about the usefulness of .cjs / .cts anyway.

JounQin · 2025-07-21T03:26:37Z

can node --strip-types actually handle .cts?

Sure: https://github.com/unifiedjs/unified-engine/pull/85/files#diff-ecf1a139df459ba97de02629e7c9f7e416079a70e54880d4921307eb861f9c5d.

I have my doubts about the usefulness of .cjs / .cts anyway.

Good point while I think it should be discussed in another issue/PR instead?

remcohaszing · 2025-07-21T08:29:15Z

test/fixtures/rc-module-cts/.foorc.cts

+import type {Settings} from 'unified'
+
+exports.settings = {
+  foo: 'bar'
+} satisfies Settings


TypeScript doesn’t understand the exports object inside TypeScript files. Instead, you are supposed to either use the special export = syntax

Suggested change

import type {Settings} from 'unified'

exports.settings = {

foo: 'bar'

} satisfies Settings

import type {PresetSupportingSpecifiers} from 'unified'

const config: PresetSupportingSpecifiers = {

settings: {

foo: 'bar'

}

}

export = config

or use an ESM style export (doesn’t work with verbatimModuleSyntax)

Suggested change

import type {Settings} from 'unified'

exports.settings = {

foo: 'bar'

} satisfies Settings

import type {Settings} from 'unified'

export const settings: Settings = {

foo: 'bar'

}

Not all features are supported by Node type stripping.

I know, though I don’t know entirely for sure which features are or aren’t supported. If neither of these syntaxes is supported by Node.js type stripping, then it doesn’t support .cts.

import type {Settings} from 'unified' work well in .cts, and .mts also doesn't support all TypeScript features, both of them are partial supported, I treat .cts same as .mts.

I consider a module format supported, if there’s a way to import and export things in a way that TypeScript understands. In CJS, for imports means at least one of:

import module = require('module') import {member} from 'module'

And for exports that means at least one of:

export = {} export const member = {}

If there’s no (proper) way to import or export from a .cts file, then it’s not properly supported. In that case IMO we should not support it either, as it promotes writing incorrect TypeScript code.

The test case is still a valid .cts usage, import for typings, exports for runtime codes.

We're talking about Node type stripping, and it's how .cts works in Node itself which is partial support.

Using .cts doesn't mean all module features are supported.

So IMO, .cts is supported by Node itself this way, then we could support how it works.

It’s not valid .cts usage. The use of the module, exports, or require variables in .cts is a hacky workaround. It only works, because the file isn’t imported by user code.

We shouldn’t promote this anti-pattern, especially considering this is already a topic of confusion in the TypeScript community.

feat: add TypeScript related extensions support

dc926b4

close #84 Signed-off-by: JounQin <[email protected]>

JounQin requested a review from Copilot July 8, 2025 04:43

github-actions bot added 👋 phase/new Post is being triaged automatically 🤞 phase/open Post is being triaged manually and removed 👋 phase/new Post is being triaged automatically labels Jul 8, 2025

Copilot AI reviewed Jul 8, 2025

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JounQin added 🦋 type/enhancement This is great to have and removed 🤞 phase/open Post is being triaged manually labels Jul 8, 2025

JounQin requested review from ChristianMurphy, remcohaszing and wooorm July 8, 2025 13:57

wooorm reviewed Jul 10, 2025

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ChristianMurphy approved these changes Jul 18, 2025

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test: add related docs and tests

d740285

JounQin requested a review from wooorm July 21, 2025 04:07

remcohaszing requested changes Jul 21, 2025

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JounQin commented Jul 8, 2025

Initial checklist

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