Prefer JS over TS in extension resolve

[lifeiscontent]

this fixes an issue when next.js is loading packages using typescript that compile their typescript code in-line with their .ts files.

e.g.

./
./a.ts => ./a.js
./b.ts => ./b.js

which would result in

./
./a.js
./a.ts
./b.js
./b.ts

[ijjk]

Stats from current PR

Default Server Mode

General

	zeit/next.js canary	lifeiscontent/next.js patch-1	Change
buildDuration	13.8s	13.7s	-49ms
nodeModulesSize	48.9 MB	48.9 MB	✓

Client Bundles (main, webpack, commons)

	zeit/next.js canary	lifeiscontent/next.js patch-1	Change
main-HASH.js gzip	5.13 kB	5.13 kB	✓
webpack-HASH.js gzip	746 B	746 B	✓
4952ddcd88e7..54d3.js gzip	4.68 kB	4.68 kB	✓
commons.HASH.js gzip	4.06 kB	4.06 kB	✓
de003c3a9d30..4cf7.js gzip	13.7 kB	13.7 kB	✓
framework.HASH.js gzip	39.1 kB	39.1 kB	✓
Overall change	67.5 kB	67.5 kB	✓

Client Bundles (main, webpack, commons) Modern

	zeit/next.js canary	lifeiscontent/next.js patch-1	Change
main-HASH.module.js gzip	4.19 kB	4.19 kB	✓
webpack-HASH..dule.js gzip	746 B	746 B	✓
4952ddcd88e7..dule.js gzip	5.56 kB	5.56 kB	✓
de003c3a9d30..dule.js gzip	12.5 kB	12.5 kB	✓
framework.HA..dule.js gzip	39.1 kB	39.1 kB	✓
Overall change	62.1 kB	62.1 kB	✓

Legacy Client Bundles (polyfills)

	zeit/next.js canary	lifeiscontent/next.js patch-1	Change
polyfills-HASH.js gzip	4.76 kB	4.76 kB	✓
Overall change	4.76 kB	4.76 kB	✓

Client Pages

	zeit/next.js canary	lifeiscontent/next.js patch-1	Change
_app.js gzip	1.33 kB	1.33 kB	✓
_error.js gzip	4.07 kB	4.07 kB	✓
hooks.js gzip	779 B	779 B	✓
index.js gzip	222 B	222 B	✓
link.js gzip	2.9 kB	2.9 kB	✓
routerDirect.js gzip	283 B	283 B	✓
withRouter.js gzip	282 B	282 B	✓
Overall change	9.87 kB	9.87 kB	✓

Client Pages Modern

	zeit/next.js canary	lifeiscontent/next.js patch-1	Change
_app.module.js gzip	757 B	757 B	✓
_error.module.js gzip	3.06 kB	3.06 kB	✓
hooks.module.js gzip	371 B	371 B	✓
index.module.js gzip	212 B	212 B	✓
link.module.js gzip	2.47 kB	2.47 kB	✓
routerDirect..dule.js gzip	273 B	273 B	✓
withRouter.m..dule.js gzip	272 B	272 B	✓
Overall change	7.41 kB	7.41 kB	✓

Client Build Manifests

	zeit/next.js canary	lifeiscontent/next.js patch-1	Change
_buildManifest.js gzip	61 B	61 B	✓
_buildManife..dule.js gzip	61 B	61 B	✓
Overall change	122 B	122 B	✓

Rendered Page Sizes

	zeit/next.js canary	lifeiscontent/next.js patch-1	Change
index.html gzip	1.02 kB	1.02 kB	✓
link.html gzip	1.03 kB	1.03 kB	✓
withRouter.html gzip	1.02 kB	1.02 kB	✓
Overall change	3.07 kB	3.07 kB	✓

---

Serverless Mode

General

	zeit/next.js canary	lifeiscontent/next.js patch-1	Change
buildDuration	14.3s	14s	-291ms
nodeModulesSize	48.9 MB	48.9 MB	✓

Client Bundles (main, webpack, commons)

	zeit/next.js canary	lifeiscontent/next.js patch-1	Change
main-HASH.js gzip	5.13 kB	5.13 kB	✓
webpack-HASH.js gzip	746 B	746 B	✓
4952ddcd88e7..54d3.js gzip	4.68 kB	4.68 kB	✓
commons.HASH.js gzip	4.06 kB	4.06 kB	✓
de003c3a9d30..4cf7.js gzip	13.7 kB	13.7 kB	✓
framework.HASH.js gzip	39.1 kB	39.1 kB	✓
Overall change	67.5 kB	67.5 kB	✓

Client Bundles (main, webpack, commons) Modern

	zeit/next.js canary	lifeiscontent/next.js patch-1	Change
main-HASH.module.js gzip	4.19 kB	4.19 kB	✓
webpack-HASH..dule.js gzip	746 B	746 B	✓
4952ddcd88e7..dule.js gzip	5.56 kB	5.56 kB	✓
de003c3a9d30..dule.js gzip	12.5 kB	12.5 kB	✓
framework.HA..dule.js gzip	39.1 kB	39.1 kB	✓
Overall change	62.1 kB	62.1 kB	✓

Legacy Client Bundles (polyfills)

	zeit/next.js canary	lifeiscontent/next.js patch-1	Change
polyfills-HASH.js gzip	4.76 kB	4.76 kB	✓
Overall change	4.76 kB	4.76 kB	✓

Client Pages

	zeit/next.js canary	lifeiscontent/next.js patch-1	Change
_app.js gzip	1.33 kB	1.33 kB	✓
_error.js gzip	4.07 kB	4.07 kB	✓
hooks.js gzip	779 B	779 B	✓
index.js gzip	222 B	222 B	✓
link.js gzip	2.9 kB	2.9 kB	✓
routerDirect.js gzip	283 B	283 B	✓
withRouter.js gzip	282 B	282 B	✓
Overall change	9.87 kB	9.87 kB	✓

Client Pages Modern

	zeit/next.js canary	lifeiscontent/next.js patch-1	Change
_app.module.js gzip	757 B	757 B	✓
_error.module.js gzip	3.06 kB	3.06 kB	✓
hooks.module.js gzip	371 B	371 B	✓
index.module.js gzip	212 B	212 B	✓
link.module.js gzip	2.47 kB	2.47 kB	✓
routerDirect..dule.js gzip	273 B	273 B	✓
withRouter.m..dule.js gzip	272 B	272 B	✓
Overall change	7.41 kB	7.41 kB	✓

Client Build Manifests

	zeit/next.js canary	lifeiscontent/next.js patch-1	Change
_buildManifest.js gzip	61 B	61 B	✓
_buildManife..dule.js gzip	61 B	61 B	✓
Overall change	122 B	122 B	✓

Serverless bundles

	zeit/next.js canary	lifeiscontent/next.js patch-1	Change
_error.js gzip	77.8 kB	77.8 kB	✓
hooks.html gzip	1.06 kB	1.06 kB	✓
index.js gzip	78 kB	78 kB	✓
link.js gzip	80.4 kB	80.4 kB	✓
routerDirect.js gzip	78.1 kB	78.1 kB	✓
withRouter.js gzip	78.1 kB	78.1 kB	✓
Overall change	393 kB	393 kB	✓

Commit: 3a8b967

[timneutkens]

That sounds like a bug in the particular package (wrong publish). Also note that next does not compile node_modules, meaning you’re customizing webpack config to achieve that. Changing this will make resolving in typescript projects slower.

[lifeiscontent]

@timneutkens every other framework (gatsby/create-react-app) resolves node_modules via JS not TS.

this might not be the right fix, but it definitely feels like a bug somewhere in the pipeline.

Within the typescript ecosystem its pretty common to compile your JS files along side your TS.

just because you haven't happened to use a node_module which does this doesn't make it not valid.

once its a node_module, (after compilation/published) it would seem pretty weird to consume TS. (which is currently happening)

[Timer]

This seems breaking, however, I wouldn't mind changing this in the future (Next 10).

[lifeiscontent]

@timneutkens also for the record, this wouldn't be an issue (for me) if styled-jsx worked in typescript alone, but since it doesn't I have to use babel to run the babel transforms to get the UI Kit I'm building to work correctly in different projects.

[timneutkens]

Did a bunch more investigation into this and it seems that the TS compiler prefers .js files too so let's mirror that behavior, could you open a new PR and add tests for this behavior in test/integration/typescript.

I'll have to close this PR as it's fork has disappeared and I can't do a checkout for it.