Change default typescript moduleResolution to bundler to match nextjs heuristics of using webpack/turbopack #75805

fuxingloh · 2025-02-08T06:44:08Z

Piggybacking on top of #51957
I believe the default generated tsconfig.json module resolution should be bundler for better DevEx and typescript language server compatibility—matching nextjs heuristics of using webpack/turbopack.

          "module": "esnext",
-         "moduleResolution": "node",
+         "moduleResolution": "bundler",
          "noEmit": true,

I started a new NextJS project manually (nextra to be precise) instead of using create-next-app, ran pnpm run dev and got an TS error/warning. The typescript language server was complaining that it doesn't understand the import semantics:

TS2307: Cannot find module nextra/ page-map or its corresponding type declarations.
There are types at
  /Users/fuxingloh/projects/some-docs/node_modules/nextra/dist/server/page-map/index.d.ts
,but this result could not be resolved under your current moduleResolution setting. Consider updating to node16, nodenext, or bundler

I ditched the manual setup and instead used create-next-app to set it up. I saw the tsconfig.json provided in create-next-app was different from the one created by "We detected TypeScript in your project and created a".

… webpack/turbppack

ijjk · 2025-02-08T06:44:33Z

Allow CI Workflow Run

approve CI run for commit: 8170ec6

Note: this should only be enabled once the PR is ready to go and can only be enabled by a maintainer

eps1lon

Basically just completing #51957. Let's see what CI says.

Thank you.

ijjk · 2025-02-09T11:50:01Z

Failing test suites

Commit: 097748a

pnpm test-dev-turbo test/development/correct-tsconfig-defaults/index.test.ts (turbopack)

correct tsconfig.json defaults > should add moduleResolution when generating tsconfig.json in dev
correct tsconfig.json defaults > should not warn for moduleResolution when already present and valid

Expand output

● correct tsconfig.json defaults › should add moduleResolution when generating tsconfig.json in dev

expect(received).toEqual(expected) // deep equality

- Expected  -  2
+ Received  + 18

- ObjectContaining {
-   "moduleResolution": "node",
+ Object {
+   "allowJs": true,
+   "esModuleInterop": true,
+   "incremental": true,
+   "isolatedModules": true,
+   "jsx": "preserve",
+   "lib": Array [
+     "dom",
+     "dom.iterable",
+     "esnext",
+   ],
+   "module": "esnext",
+   "moduleResolution": "bundler",
+   "noEmit": true,
+   "resolveJsonModule": true,
+   "skipLibCheck": true,
+   "strict": false,
+   "target": "ES2017",
  }

  39 |       expect(next.cliOutput).not.toContain('moduleResolution')
  40 |
> 41 |       expect(tsconfig.compilerOptions).toEqual(
     |                                        ^
  42 |         expect.objectContaining({ moduleResolution: 'node' })
  43 |       )
  44 |     } finally {

  at Object.toEqual (development/correct-tsconfig-defaults/index.test.ts:41:40)

● correct tsconfig.json defaults › should not warn for moduleResolution when already present and valid

expect(received).toEqual(expected) // deep equality

- Expected  -  2
+ Received  + 18

- ObjectContaining {
-   "moduleResolution": "node",
+ Object {
+   "allowJs": true,
+   "esModuleInterop": true,
+   "incremental": true,
+   "isolatedModules": true,
+   "jsx": "preserve",
+   "lib": Array [
+     "dom",
+     "dom.iterable",
+     "esnext",
+   ],
+   "module": "esnext",
+   "moduleResolution": "bundler",
+   "noEmit": true,
+   "resolveJsonModule": true,
+   "skipLibCheck": true,
+   "strict": false,
+   "target": "ES2017",
  }

  57 |       const tsconfig = JSON.parse(await next.readFile('tsconfig.json'))
  58 |
> 59 |       expect(tsconfig.compilerOptions).toEqual(
     |                                        ^
  60 |         expect.objectContaining({ moduleResolution: 'node' })
  61 |       )
  62 |       expect(next.cliOutput).not.toContain('moduleResolution')

  at Object.toEqual (development/correct-tsconfig-defaults/index.test.ts:59:40)

Read more about building and testing Next.js in contributing.md.

pnpm test-start-turbo test/e2e/app-dir/next-dist-client-esm-import/next-dist-client-esm-import.test.ts (turbopack)

next-dist-client-esm-import > should resolve ESM modules that have "next/dist/client" in their filename

Expand output

● next-dist-client-esm-import › should resolve ESM modules that have "next/dist/client" in their filename

next build failed with code/signal 1

   98 |           if (code || signal)
   99 |             reject(
> 100 |               new Error(`next build failed with code/signal ${code || signal}`)
      |               ^
  101 |             )
  102 |           else resolve()
  103 |         })

  at ChildProcess.<anonymous> (lib/next-modes/next-start.ts:100:15)

Read more about building and testing Next.js in contributing.md.

pnpm test test/integration/tsconfig-verifier/test/index.test.js

tsconfig.json verifier > Creates a default tsconfig.json when one is missing
tsconfig.json verifier > Works with an empty tsconfig.json (docs)
tsconfig.json verifier > Updates an existing tsconfig.json without losing comments
tsconfig.json verifier > allows you to set commonjs module mode
tsconfig.json verifier > allows you to set es2020 module mode
tsconfig.json verifier > allows you to set target mode
tsconfig.json verifier > allows you to set verbatimModuleSyntax true without adding isolatedModules
tsconfig.json verifier > allows you to set verbatimModuleSyntax true via extends without adding isolatedModules

Expand output

● tsconfig.json verifier › Creates a default tsconfig.json when one is missing

expect(received).toMatchInlineSnapshot(snapshot)

Snapshot name: `tsconfig.json verifier Creates a default tsconfig.json when one is missing 1`

- Snapshot  - 1
+ Received  + 1

@@ -11,11 +11,11 @@
      "strict": false,
      "noEmit": true,
      "incremental": true,
      "module": "esnext",
      "esModuleInterop": true,
-     "moduleResolution": "node",
+     "moduleResolution": "bundler",
      "resolveJsonModule": true,
      "isolatedModules": true,
      "jsx": "preserve",
      "plugins": [
        {

  25 |       const { code } = await nextBuild(appDir)
  26 |       expect(code).toBe(0)
> 27 |       expect(await readFile(tsConfig, 'utf8')).toMatchInlineSnapshot(`
     |                                                ^
  28 |         "{
  29 |           "compilerOptions": {
  30 |             "target": "ES2017",

  at Object.toMatchInlineSnapshot (integration/tsconfig-verifier/test/index.test.js:27:48)

● tsconfig.json verifier › Works with an empty tsconfig.json (docs)

expect(received).toMatchInlineSnapshot(snapshot)

Snapshot name: `tsconfig.json verifier Works with an empty tsconfig.json (docs) 1`

- Snapshot  - 1
+ Received  + 1

@@ -11,11 +11,11 @@
      "strict": false,
      "noEmit": true,
      "incremental": true,
      "module": "esnext",
      "esModuleInterop": true,
-     "moduleResolution": "node",
+     "moduleResolution": "bundler",
      "resolveJsonModule": true,
      "isolatedModules": true,
      "jsx": "preserve",
      "plugins": [
        {

  80 |       expect(code).toBe(0)
  81 |
> 82 |       expect(await readFile(tsConfig, 'utf8')).toMatchInlineSnapshot(`
     |                                                ^
  83 |         "{
  84 |           "compilerOptions": {
  85 |             "target": "ES2017",

  at Object.toMatchInlineSnapshot (integration/tsconfig-verifier/test/index.test.js:82:48)

● tsconfig.json verifier › Updates an existing tsconfig.json without losing comments

expect(received).toMatchInlineSnapshot(snapshot)

Snapshot name: `tsconfig.json verifier Updates an existing tsconfig.json without losing comments 1`

- Snapshot  - 1
+ Received  + 1

@@ -16,11 +16,11 @@
      "allowJs": true,
      "skipLibCheck": true,
      "strict": false,
      "noEmit": true,
      "incremental": true,
-     "moduleResolution": "node",
+     "moduleResolution": "bundler",
      "resolveJsonModule": true,
      "isolatedModules": true,
      "jsx": "preserve",
      "plugins": [
        {

  147 |       // Weird comma placement until this issue is resolved:
  148 |       // https://github.com/kaelzhang/node-comment-json/issues/21
> 149 |       expect(await readFile(tsConfig, 'utf8')).toMatchInlineSnapshot(`
      |                                                ^
  150 |         "// top-level comment
  151 |         {
  152 |           // in-object comment 1

  at Object.toMatchInlineSnapshot (integration/tsconfig-verifier/test/index.test.js:149:48)

● tsconfig.json verifier › allows you to set commonjs module mode

command failed with code 1 signal null
 ⚠ Linting is disabled.
   No config file found
   No config file found
   ▲ Next.js 15.2.0-canary.46

   Creating an optimized production build ...
   No config file found
   No config file found
   No config file found
 ✓ Compiled successfully
   Checking validity of types ...

   We detected TypeScript in your project and reconfigured your tsconfig.json file for you. Strict-mode is set to false by default.
   The following suggested values were added to your tsconfig.json. These values can be changed to fit your project's needs:

   	- target was set to ES2017 (For top-level `await`. Note: Next.js only polyfills for the esmodules target.)
   	- lib was set to dom,dom.iterable,esnext
   	- allowJs was set to true
   	- skipLibCheck was set to true
   	- strict was set to false
   	- noEmit was set to true
   	- incremental was set to true
   	- include was set to ['next-env.d.ts', '.next/types/**/*.ts', '**/*.ts', '**/*.tsx']
   	- plugins was updated to add { name: 'next' }
   	- strictNullChecks was set to true
   	- exclude was set to ['node_modules']

   The following mandatory changes were made to your tsconfig.json:

   	- esModuleInterop was set to true (requirement for SWC / babel)
   	- moduleResolution was set to bundler (to match webpack resolution)
   	- resolveJsonModule was set to true (to match webpack resolution)
   	- isolatedModules was set to true (requirement for SWC / Babel)
   	- jsx was set to preserve (next.js implements its own optimized jsx transform)



===== TS errors =====

[Test Mode] Type error: Option 'bundler' can only be used when 'module' is set to 'preserve' or to 'es2015' or later.


===== TS errors =====


Failed to compile.

Type error: Option 'bundler' can only be used when 'module' is set to 'preserve' or to 'es2015' or later.

Next.js build worker exited with code: 1 and signal: null

  312 |       ) {
  313 |         return reject(
> 314 |           new Error(
      |           ^
  315 |             `command failed with code ${code} signal ${signal}\n${mergedStdio}`
  316 |           )
  317 |         )

  at ChildProcess.<anonymous> (lib/next-test-utils.ts:314:11)

● tsconfig.json verifier › allows you to set es2020 module mode

expect(received).toMatchInlineSnapshot(snapshot)

Snapshot name: `tsconfig.json verifier allows you to set es2020 module mode 1`

- Snapshot  - 1
+ Received  + 1

@@ -11,11 +11,11 @@
      "allowJs": true,
      "skipLibCheck": true,
      "strict": false,
      "noEmit": true,
      "incremental": true,
-     "moduleResolution": "node",
+     "moduleResolution": "bundler",
      "resolveJsonModule": true,
      "isolatedModules": true,
      "jsx": "preserve",
      "plugins": [
        {

  259 |       expect(code).toBe(0)
  260 |
> 261 |       expect(await readFile(tsConfig, 'utf8')).toMatchInlineSnapshot(`
      |                                                ^
  262 |         "{
  263 |           "compilerOptions": {
  264 |             "esModuleInterop": true,

  at Object.toMatchInlineSnapshot (integration/tsconfig-verifier/test/index.test.js:261:48)

● tsconfig.json verifier › allows you to set target mode

expect(received).toMatchInlineSnapshot(snapshot)

Snapshot name: `tsconfig.json verifier allows you to set target mode 1`

- Snapshot  - 1
+ Received  + 1

@@ -11,11 +11,11 @@
      "strict": false,
      "noEmit": true,
      "incremental": true,
      "module": "esnext",
      "esModuleInterop": true,
-     "moduleResolution": "node",
+     "moduleResolution": "bundler",
      "resolveJsonModule": true,
      "isolatedModules": true,
      "jsx": "preserve",
      "plugins": [
        {

  424 |       expect(code).toBe(0)
  425 |
> 426 |       expect(await readFile(tsConfig, 'utf8')).toMatchInlineSnapshot(`
      |                                                ^
  427 |               "{
  428 |                 "compilerOptions": {
  429 |                   "target": "es2022",

  at Object.toMatchInlineSnapshot (integration/tsconfig-verifier/test/index.test.js:426:48)

● tsconfig.json verifier › allows you to set verbatimModuleSyntax true without adding isolatedModules

expect(received).toMatchInlineSnapshot(snapshot)

Snapshot name: `tsconfig.json verifier allows you to set verbatimModuleSyntax true without adding isolatedModules 1`

- Snapshot  - 1
+ Received  + 1

@@ -12,11 +12,11 @@
      "strict": false,
      "noEmit": true,
      "incremental": true,
      "module": "esnext",
      "esModuleInterop": true,
-     "moduleResolution": "node",
+     "moduleResolution": "bundler",
      "resolveJsonModule": true,
      "jsx": "preserve",
      "plugins": [
        {
          "name": "next"

  536 |       expect(code).toBe(0)
  537 |
> 538 |       expect(await readFile(tsConfig, 'utf8')).toMatchInlineSnapshot(`
      |                                                ^
  539 |         "{
  540 |           "compilerOptions": {
  541 |             "verbatimModuleSyntax": true,

  at Object.toMatchInlineSnapshot (integration/tsconfig-verifier/test/index.test.js:538:48)

● tsconfig.json verifier › allows you to set verbatimModuleSyntax true via extends without adding isolatedModules

expect(received).toMatchInlineSnapshot(snapshot)

Snapshot name: `tsconfig.json verifier allows you to set verbatimModuleSyntax true via extends without adding isolatedModules 1`

- Snapshot  - 1
+ Received  + 1

@@ -12,11 +12,11 @@
      "strict": false,
      "noEmit": true,
      "incremental": true,
      "module": "esnext",
      "esModuleInterop": true,
-     "moduleResolution": "node",
+     "moduleResolution": "bundler",
      "resolveJsonModule": true,
      "jsx": "preserve",
      "plugins": [
        {
          "name": "next"

  594 |       expect(code).toBe(0)
  595 |
> 596 |       expect(await readFile(tsConfig, 'utf8')).toMatchInlineSnapshot(`
      |                                                ^
  597 |         "{
  598 |           "extends": "./tsconfig.base.json",
  599 |           "compilerOptions": {

  at Object.toMatchInlineSnapshot (integration/tsconfig-verifier/test/index.test.js:596:48)

Read more about building and testing Next.js in contributing.md.

ijjk · 2025-02-09T11:53:32Z

Stats from current PR

Default Build (Increase detected ⚠️)

General

	vercel/next.js canary	fuxingloh/next.js patch-module-resolution	Change
buildDuration	19s	17.3s	N/A
buildDurationCached	16.2s	13.5s	N/A
nodeModulesSize	393 MB	393 MB	N/A
nextStartRea..uration (ms)	446ms	447ms	N/A

Client Bundles (main, webpack)

	vercel/next.js canary	fuxingloh/next.js patch-module-resolution	Change
5306-HASH.js gzip	54.3 kB	54.3 kB	N/A
8276.HASH.js gzip	169 B	168 B	N/A
8377-HASH.js gzip	5.46 kB	5.46 kB	N/A
bccd1874-HASH.js gzip	53 kB	53 kB	✓
framework-HASH.js gzip	57.5 kB	57.5 kB	N/A
main-app-HASH.js gzip	245 B	246 B	N/A
main-HASH.js gzip	34.6 kB	34.5 kB	N/A
webpack-HASH.js gzip	1.71 kB	1.71 kB	N/A
Overall change	53 kB	53 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	fuxingloh/next.js patch-module-resolution	Change
polyfills-HASH.js gzip	39.4 kB	39.4 kB	✓
Overall change	39.4 kB	39.4 kB	✓

Client Pages

	vercel/next.js canary	fuxingloh/next.js patch-module-resolution	Change
_app-HASH.js gzip	193 B	193 B	✓
_error-HASH.js gzip	193 B	193 B	✓
amp-HASH.js gzip	512 B	510 B	N/A
css-HASH.js gzip	343 B	342 B	N/A
dynamic-HASH.js gzip	1.84 kB	1.84 kB	✓
edge-ssr-HASH.js gzip	265 B	265 B	✓
head-HASH.js gzip	363 B	362 B	N/A
hooks-HASH.js gzip	393 B	392 B	N/A
image-HASH.js gzip	4.59 kB	4.58 kB	N/A
index-HASH.js gzip	268 B	268 B	✓
link-HASH.js gzip	2.35 kB	2.35 kB	N/A
routerDirect..HASH.js gzip	328 B	328 B	✓
script-HASH.js gzip	397 B	397 B	✓
withRouter-HASH.js gzip	323 B	326 B	N/A
1afbb74e6ecf..834.css gzip	106 B	106 B	✓
Overall change	3.59 kB	3.59 kB	✓

Client Build Manifests

	vercel/next.js canary	fuxingloh/next.js patch-module-resolution	Change
_buildManifest.js gzip	748 B	747 B	N/A
Overall change	0 B	0 B	✓

Rendered Page Sizes

	vercel/next.js canary	fuxingloh/next.js patch-module-resolution	Change
index.html gzip	522 B	523 B	N/A
link.html gzip	538 B	538 B	✓
withRouter.html gzip	518 B	520 B	N/A
Overall change	538 B	538 B	✓

Edge SSR bundle Size

	vercel/next.js canary	fuxingloh/next.js patch-module-resolution	Change
edge-ssr.js gzip	130 kB	130 kB	N/A
page.js gzip	211 kB	211 kB	N/A
Overall change	0 B	0 B	✓

Middleware size

	vercel/next.js canary	fuxingloh/next.js patch-module-resolution	Change
middleware-b..fest.js gzip	676 B	671 B	N/A
middleware-r..fest.js gzip	155 B	156 B	N/A
middleware.js gzip	31.3 kB	31.3 kB	N/A
edge-runtime..pack.js gzip	844 B	844 B	✓
Overall change	844 B	844 B	✓

Next Runtimes

	vercel/next.js canary	fuxingloh/next.js patch-module-resolution	Change
app-page-exp...dev.js gzip	394 kB	394 kB	✓
app-page-exp..prod.js gzip	132 kB	132 kB	✓
app-page-tur..prod.js gzip	145 kB	145 kB	✓
app-page-tur..prod.js gzip	141 kB	141 kB	✓
app-page.run...dev.js gzip	381 kB	381 kB	✓
app-page.run..prod.js gzip	129 kB	129 kB	✓
app-route-ex...dev.js gzip	39.3 kB	39.3 kB	✓
app-route-ex..prod.js gzip	25.6 kB	25.6 kB	✓
app-route-tu..prod.js gzip	25.6 kB	25.6 kB	✓
app-route-tu..prod.js gzip	25.4 kB	25.4 kB	✓
app-route.ru...dev.js gzip	40.9 kB	40.9 kB	✓
app-route.ru..prod.js gzip	25.4 kB	25.4 kB	✓
dist_client_...dev.js gzip	356 B	356 B	✓
dist_client_...dev.js gzip	349 B	349 B	✓
pages-api-tu..prod.js gzip	9.69 kB	9.69 kB	✓
pages-api.ru...dev.js gzip	11.8 kB	11.8 kB	✓
pages-api.ru..prod.js gzip	9.68 kB	9.68 kB	✓
pages-turbo...prod.js gzip	21.9 kB	21.9 kB	✓
pages.runtim...dev.js gzip	31.5 kB	31.5 kB	✓
pages.runtim..prod.js gzip	21.9 kB	21.9 kB	✓
server.runti..prod.js gzip	60.6 kB	60.6 kB	✓
Overall change	1.67 MB	1.67 MB	✓

build cache Overall increase ⚠️

	vercel/next.js canary	fuxingloh/next.js patch-module-resolution	Change
0.pack gzip	2.11 MB	2.11 MB	N/A
index.pack gzip	75.4 kB	76.4 kB	⚠️ +1.02 kB
Overall change	75.4 kB	76.4 kB	⚠️ +1.02 kB

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Commit: 097748a

stale

eps1lon

Can you take care of updating the remaining tests?

fuxingloh · 2025-02-09T14:42:24Z

Can you take care of updating the remaining tests?

I fix a few more that are obvious to me, but I don't have a proper setup so I'm gonna stop here.

default moduleResolution: bundler to match nextjs heuristics of using…

097748a

… webpack/turbppack

ijjk added the type: next label Feb 8, 2025

fuxingloh changed the title ~~Change default typescript moduleResolution to bundler to match nextjs heuristics of using webpack/turbppack~~ Change default typescript moduleResolution to bundler to match nextjs heuristics of using webpack/turbopack Feb 8, 2025

fuxingloh marked this pull request as ready for review February 8, 2025 06:45

eps1lon previously approved these changes Feb 9, 2025

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eps1lon requested changes Feb 9, 2025

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fix some tests

8170ec6

ijjk added the tests label Feb 9, 2025

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Change default typescript moduleResolution to bundler to match nextjs heuristics of using webpack/turbopack #75805

Change default typescript moduleResolution to bundler to match nextjs heuristics of using webpack/turbopack #75805

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fuxingloh commented Feb 9, 2025

Change default typescript moduleResolution to bundler to match nextjs heuristics of using webpack/turbopack #75805

Are you sure you want to change the base?

Change default typescript moduleResolution to bundler to match nextjs heuristics of using webpack/turbopack #75805

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Failing test suites

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