Publish valid ESM types for dual output packages#120
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Pull request overview
This PR updates ts-toolkit’s packaging workflow to publish valid TypeScript declarations for dual ESM/CJS outputs and adds an arethetypeswrong export/types validation step to generated templates and this repo’s build.
Changes:
- Emit conditional
exportsentries with per-conditiontypesfor dual-output packages. - Add a build step to validate published artifacts with
@arethetypeswrong/cli(attw --pack dist), including wiring it into templates and devDependencies. - Add utilities + tests to generate
.d.mts/.d.ctssiblings and rewrite relative specifiers for ESM declaration resolution.
Reviewed changes
Copilot reviewed 5 out of 6 changed files in this pull request and generated 4 comments.
Show a summary per file
| File | Description |
|---|---|
| src/util/copy-package-json-from-config.ts | Builds new exports shapes and emits dual declaration siblings with ESM-specifier rewriting. |
| src/util/copy-package-json-from-config.spec.ts | Adds tests for conditional exports shapes and declaration emission/rewriting. |
| src/init/check-packages.ts | Ensures @arethetypeswrong/cli is installed in initialized Node projects. |
| src/init/add-scripts.ts | Adds build:* script to run attw against the packed dist output in templates. |
| package.json | Bumps version and adds attw build script + devDependency. |
| package-lock.json | Locks new @arethetypeswrong/cli dependency tree and updates version metadata. |
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tristanmenzel
approved these changes
Apr 24, 2026
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This worked well 
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4 tasks
cuzzlor
added a commit
that referenced
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Apr 28, 2026
* fix(types): rewrite .d.mts relative specifiers to .mjs
`emitDualDeclarations` was producing `.d.mts` files whose relative
specifiers ended in `.js`. Under TS's node16+ ESM resolver, a `.js`
specifier in a `.d.mts` is paired with the adjacent `.d.ts`, which —
in a dual-published package whose root `package.json` has
`"type": "commonjs"` — is treated as CJS-flavoured. Strict ESM
consumers then surface type-resolution errors against an otherwise
valid package.
`rewriteSpecifier` is only ever called for the `.d.mts` branch, so the
extension it emits should be `.mjs`, which pairs with the `.d.mts`
twin and keeps the resolution chain in ESM throughout.
The `.d.cts` branch is unaffected — those remain content-identical
copies of the source `.d.ts`, which CJS resolution handles via
extensionless specifiers.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
* test+docs: cover .mjs rewrite cases and document dual-decl emission
Tests
- Add focused unit test for the file case (was only exercised via the
integration test): `from './foo'` → `from './foo.mjs'` when `./foo.d.ts`
exists.
- Add test for resolving when only the `.d.mts` twin is present alongside
the source, exercising the second branch of `rewriteSpecifier`.
- Add test that runs all three module-specifier shapes through one pass
(`from '...'`, bare `import '...'`, dynamic `import('...')`).
Docs
- Add a `## copy-package-json` subsection covering dual-declaration
emission, the per-condition `exports` shape, and the `.mjs` rewrite
rules with the rationale for `.mjs` over `.js`.
- The original feature (PR #120) shipped without README coverage; this
fills that gap alongside the specifier-extension fix.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
* chore(release): 5.0.0-beta.1
Publishes the .d.mts specifier-extension fix so downstream packages can
drop their local workarounds (e.g. graphql-apollo-server's
build:4a-fix-dmts post-step).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
* chore(audit): bump postcss to 8.5.10 to fix GHSA-qx2v-qp2m-jg93
Resolves the moderate XSS advisory (PostCSS Stringify Output unescaped
`</style>`) reaching us via vitest > vite > postcss in dev. Within the
existing semver range; no package.json change, lockfile-only.
Surfaced by the PR check on #121.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
* docs+test: cover the .d.mts adjacency case for directory specifiers
Addresses Copilot review comments on #121. `rewriteSpecifier` already
resolves both `.d.ts` and `.d.mts` adjacents in the directory branch,
but the README bullet and the source-comment example only mentioned
`.d.ts`. Updated both to spell out either form.
Also adds a sibling unit test covering the case where only an
`index.d.mts` is present in a directory (matching the existing
"only a .d.mts twin alongside the source" test for the file case).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
* use interop: 'auto' as default for rollup CJS output
* fix default rollup external function to correctly switch between local and imported module code
---------
Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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Problem
https://arethetypeswrong.github.io/?p=%40makerx%2Fexpress-msal%40%5E2.0.0-beta.0
More details
https://github.com/arethetypeswrong/arethetypeswrong.github.io/blob/main/docs/problems/FalseCJS.md
Solution