build,deps: replace cjs-module-lexer with merve by anonrig · Pull Request #61456 · nodejs/node · GitHub

Initially started a couple of years ago, the new cjs module lexer is 25% faster for cold importing cjs files. This change introduces a new dependency and removes the old one.

Benchmark CI: https://ci.nodejs.org/view/Node.js%20benchmark/job/benchmark-node-micro-benchmarks/1784/console

                                                                                                                                                                confidence improvement accuracy (*)
esm/detect-esm-syntax.js n=10000 type='with-package-json'                                                                                                              ***      1.47 %       ±0.40%
esm/detect-esm-syntax.js n=10000 type='without-package-json'                                                                                                           ***      0.64 %       ±0.35%
esm/esm-legacyMainResolve.js resolvedFile='node_modules/non-exist' packageConfigMain='./index.js' packageJsonUrl='node_modules/test/package.json' n=10000                *      0.95 %       ±0.92%
esm/esm-legacyMainResolve.js resolvedFile='node_modules/non-exist' packageConfigMain='' packageJsonUrl='node_modules/test/package.json' n=10000                                -0.06 %       ±0.95%
esm/esm-legacyMainResolve.js resolvedFile='node_modules/test/index.js' packageConfigMain='./index.js' packageJsonUrl='node_modules/test/package.json' n=10000                  -0.72 %       ±1.02%
esm/esm-legacyMainResolve.js resolvedFile='node_modules/test/index.js' packageConfigMain='' packageJsonUrl='node_modules/test/package.json' n=10000                             0.33 %       ±0.62%
esm/esm-legacyMainResolve.js resolvedFile='node_modules/test/index.json' packageConfigMain='./index.js' packageJsonUrl='node_modules/test/package.json' n=10000                 0.38 %       ±0.98%
esm/esm-legacyMainResolve.js resolvedFile='node_modules/test/index.json' packageConfigMain='' packageJsonUrl='node_modules/test/package.json' n=10000                   **      0.84 %       ±0.61%
esm/esm-legacyMainResolve.js resolvedFile='node_modules/test/index.node' packageConfigMain='./index.js' packageJsonUrl='node_modules/test/package.json' n=10000                 0.66 %       ±1.04%
esm/esm-legacyMainResolve.js resolvedFile='node_modules/test/index.node' packageConfigMain='' packageJsonUrl='node_modules/test/package.json' n=10000                           0.21 %       ±0.92%
esm/esm-loader-defaultResolve.js specifier='./relative-existing.js' n=1000                                                                                                     -1.93 %       ±5.48%
esm/esm-loader-defaultResolve.js specifier='./relative-nonexistent.js' n=1000                                                                                                  -0.48 %       ±1.94%
esm/esm-loader-defaultResolve.js specifier='node:os' n=1000                                                                                                                    -8.43 %       ±9.28%
esm/esm-loader-defaultResolve.js specifier='node:prefixed-nonexistent' n=1000                                                                                                  -8.48 %      ±10.15%
esm/esm-loader-defaultResolve.js specifier='unprefixed-existing' n=1000                                                                                                         0.56 %       ±3.21%
esm/esm-loader-defaultResolve.js specifier='unprefixed-nonexistent' n=1000                                                                                                     -0.08 %       ±1.73%
esm/esm-loader-import.js specifier='./relative-existing.js' n=1000                                                                                                       *      5.62 %       ±5.09%
esm/esm-loader-import.js specifier='./relative-nonexistent.js' n=1000                                                                                                           1.53 %       ±2.90%
esm/esm-loader-import.js specifier='data:text/javascript,{i}' n=1000                                                                                                            1.47 %       ±2.73%
esm/esm-loader-import.js specifier='node:os' n=1000                                                                                                                             0.43 %       ±7.59%
esm/esm-loader-import.js specifier='node:prefixed-nonexistent' n=1000                                                                                                           2.29 %       ±3.67%
esm/import-cjs.js type='cold'                                                                                                                                          ***     26.83 %       ±0.58%
esm/import-cjs.js type='warm'                                                                                                                                          ***     11.95 %       ±0.14%
esm/import-esm-reload.js n=1000 count=1                                                                                                                                         0.08 %       ±1.04%
esm/import-esm-reload.js n=1000 count=100                                                                                                                                *      0.99 %       ±0.92%
esm/import-meta.js valuesToRead='dirname-and-filename' n=1000                                                                                                           **      1.11 %       ±0.75%
esm/import-meta.js valuesToRead='dirname' n=1000                                                                                                                                0.50 %       ±0.67%
esm/import-meta.js valuesToRead='filename' n=1000                                                                                                                       **      1.17 %       ±0.76%
esm/import-meta.js valuesToRead='url' n=1000                                                                                                                                   -0.57 %       ±0.77%
esm/require-esm.js n=1000 exports='default' type='access'                                                                                                                       0.77 %       ±1.21%
esm/require-esm.js n=1000 exports='default' type='all'                                                                                                                          1.31 %       ±1.75%
esm/require-esm.js n=1000 exports='default' type='load'                                                                                                                         0.06 %       ±1.96%
esm/require-esm.js n=1000 exports='named' type='access'                                                                                                                         0.79 %       ±1.05%
esm/require-esm.js n=1000 exports='named' type='all'                                                                                                                           -0.54 %       ±1.98%
esm/require-esm.js n=1000 exports='named' type='load'                                                                                                                          -0.90 %       ±2.32%

Review requested:

@nodejs/gyp
@nodejs/security-wg

Codecov Report

❌ Patch coverage is 78.84615% with 11 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.78%. Comparing base (98d2331) to head (474c7e1).
⚠️ Report is 53 commits behind head on main.

Files with missing lines	Patch %	Lines
src/node_cjs_lexer.cc	77.55%	8 Missing and 3 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #61456      +/-   ##
==========================================
- Coverage   89.85%   89.78%   -0.07%     
==========================================
  Files         671      673       +2     
  Lines      203166   203822     +656     
  Branches    39057    39183     +126     
==========================================
+ Hits       182554   183001     +447     
- Misses      12967    13139     +172     
- Partials     7645     7682      +37

Files with missing lines	Coverage Δ
lib/internal/modules/esm/translators.js	92.58% <100.00%> (-0.39%)	⬇️
src/node_binding.cc	82.74% <ø> (ø)
src/node_builtins.cc	76.33% <ø> (+0.14%)	⬆️
src/node_metadata.cc	92.75% <100.00%> (+0.32%)	⬆️
src/node_cjs_lexer.cc	77.55% <77.55%> (ø)

... and 72 files with indirect coverage changes

🚀 New features to boost your workflow:

❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

Where does this new dep live?

Notable changes: async_hooks: * (SEMVER-MINOR) add trackPromises option to createHook() (Joyee Cheung) #61415 build,deps: * replace cjs-module-lexer with merve (Yagiz Nizipli) #61456 deps: * (SEMVER-MINOR) add LIEF as a dependency (Joyee Cheung) #61167 * (SEMVER-MINOR) add tools and scripts to pull LIEF as a dependency (Joyee Cheung) #61167 events: * (SEMVER-MINOR) repurpose `events.listenerCount()` to accept EventTargets (René) #60214 fs: * (SEMVER-MINOR) add ignore option to fs.watch (Matteo Collina) #61433 http: * (SEMVER-MINOR) add http.setGlobalProxyFromEnv() (Joyee Cheung) #60953 module: * (SEMVER-MINOR) allow subpath imports that start with `#/` (Jan Martin) #60864 process: * (SEMVER-MINOR) preserve AsyncLocalStorage in queueMicrotask only when needed (Gürgün Dayıoğlu) #60913 sea: * (SEMVER-MINOR) split sea binary manipulation code (Joyee Cheung) #61167 sqlite: * (SEMVER-MINOR) enable defensive mode by default (Bart Louwers) #61266 * (SEMVER-MINOR) add sqlite prepare options args (Guilherme Araújo) #61311 src: * (SEMVER-MINOR) add initial support for ESM in embedder API (Joyee Cheung) #61548 stream: * (SEMVER-MINOR) add bytes() method to stream/consumers (wantaek) #60426 * (SEMVER-MINOR) do not pass `readable.compose()` output via `Readable.from()` (René) #60907 test: * (SEMVER-MINOR) use fixture directories for sea tests (Joyee Cheung) #61167 test_runner: * (SEMVER-MINOR) add env option to run function (Ethan Arrowood) #61367 * (SEMVER-MINOR) support expecting a test-case to fail (Jacob Smith) #60669 util: * (SEMVER-MINOR) add convertProcessSignalToExitCode utility (Erick Wendel) #60963 PR-URL: #61924

PR-URL: #61456 Reviewed-By: Guy Bedford <guybedford@gmail.com> Reviewed-By: Daniel Lemire <daniel@lemire.me> Reviewed-By: Richard Lau <richard.lau@ibm.com>

Notable changes: async_hooks: * (SEMVER-MINOR) add `trackPromises` option to `createHook()` (Joyee Cheung) #61415 build,deps: * replace cjs-module-lexer with merve (Yagiz Nizipli) #61456 deps: * (SEMVER-MINOR) add LIEF as a dependency (Joyee Cheung) #61167 events: * (SEMVER-MINOR) repurpose `events.listenerCount()` to accept `EventTarget`s (René) #60214 fs: * (SEMVER-MINOR) add `ignore` option to `fs.watch` (Matteo Collina) #61433 http: * (SEMVER-MINOR) add `http.setGlobalProxyFromEnv()` (Joyee Cheung) #60953 module: * (SEMVER-MINOR) allow subpath imports that start with `#/` (Jan Martin) #60864 process: * (SEMVER-MINOR) preserve `AsyncLocalStorage` in `queueMicrotask` only when needed (Gürgün Dayıoğlu) #60913 sea: * (SEMVER-MINOR) split sea binary manipulation code (Joyee Cheung) #61167 sqlite: * (SEMVER-MINOR) enable defensive mode by default (Bart Louwers) #61266 * (SEMVER-MINOR) add sqlite prepare options args (Guilherme Araújo) #61311 src: * (SEMVER-MINOR) add initial support for ESM in embedder API (Joyee Cheung) #61548 stream: * (SEMVER-MINOR) add `bytes()` method to `node:stream/consumers` (wantaek) #60426 * (SEMVER-MINOR) do not pass `readable.compose()` output via `Readable.from()` (René) #60907 test: * (SEMVER-MINOR) use fixture directories for sea tests (Joyee Cheung) #61167 test_runner: * (SEMVER-MINOR) add `env` option to `run` function (Ethan Arrowood) #61367 * (SEMVER-MINOR) support expecting a test-case to fail (Jacob Smith) #60669 util: * (SEMVER-MINOR) add `convertProcessSignalToExitCode` utility (Erick Wendel) #60963 PR-URL: #61924

nodejs/node#61456

* chore: bump node in DEPS to v24.14.0 * lib: prefer call() over apply() if argument list is not array nodejs/node#60796 * build,deps: replace cjs-module-lexer with merve nodejs/node#61456 * chore: fixup patch indices * test: use fixture directories for sea tests nodejs/node#61167 * src: throw RangeError on failed ArrayBuffer BackingStore allocation nodejs/node#61480 --------- Co-authored-by: electron-roller[bot] <84116207+electron-roller[bot]@users.noreply.github.com> Co-authored-by: Shelley Vohr <shelley.vohr@gmail.com>

nodejs/node#61456

* chore: bump node in DEPS to v24.14.0 * lib: prefer call() over apply() if argument list is not array nodejs/node#60796 * build,deps: replace cjs-module-lexer with merve nodejs/node#61456 * test: use fixture directories for sea tests nodejs/node#61167 * src: throw RangeError on failed ArrayBuffer BackingStore allocation * chore: fixup patch indices --------- Co-authored-by: electron-roller[bot] <84116207+electron-roller[bot]@users.noreply.github.com> Co-authored-by: Shelley Vohr <shelley.vohr@gmail.com>

* chore: bump node in DEPS to v24.14.0 * lib: prefer call() over apply() if argument list is not array nodejs/node#60796 * build,deps: replace cjs-module-lexer with merve nodejs/node#61456 * chore: fixup patch indices * test: use fixture directories for sea tests nodejs/node#61167 * src: throw RangeError on failed ArrayBuffer BackingStore allocation * chore: fixup crypto patch --------- Co-authored-by: electron-roller[bot] <84116207+electron-roller[bot]@users.noreply.github.com> Co-authored-by: Shelley Vohr <shelley.vohr@gmail.com>

I've been having odd issues with my testing setup; I don't fully understand the problem, and haven't been able to reproduce it outside of a nix build, but I've been able to bisect the issue down to 68da144.

Unfortunately, I haven't been able to pare this down to a minimal reproducer, nor can I share the full project; I'm running firefox playwright tests against a project built with vite, and the breakage seems to boil down to a difference in how import * behaves in the code built by vite running in the browser, which seems pretty cursed!

My import looks like this:

import * as Chord from "@tonaljs/chord"

My code then uses Chord.get(), which works fine prior to this change and breaks afterwards with "Chord.get is not a function".

Logging the imported Chord object shed some light on the problem:

[Module: null prototype] {                                                                                                                                                                 
  chord: [Function (anonymous)],                                                                                                                                                           
  chordScales: [Function: chordScales],       
  default: {                                  
    chord: [Getter],                                                                                                                                                                       
    chordScales: [Getter],                                                                   
    default: [Getter],                        
    degrees: [Getter],                                                                       
    deprecate: [Getter],                                                                     
    detect: [Getter],                                                                        
    extended: [Getter],                                                                                                                                                                    
    get: [Getter],                                                                                                                                                                         
    getChord: [Getter],                                                                                                                                                                    
    reduced: [Getter],                                                                                                                                                                     
    steps: [Getter],                                                                                                                                                                       
    tokenize: [Getter],                                                                                                                                                                    
    transpose: [Getter]                                                                      
  },                                                                                                                                                                                       
  degrees: [Function: degrees],                                                                                                                                                            
  deprecate: [Function: deprecate],                                                                                                                                                        
  detect: [Function: detect],                                                                
  extended: [Function: extended],                                                            
  'module.exports': {                                                                        
    chord: [Getter],                                                                         
    chordScales: [Getter],                                                                                                                                                                 
    default: [Getter],                        
    degrees: [Getter],                                                                       
    deprecate: [Getter],                                                                     
    detect: [Getter],                                                                        
    extended: [Getter],                                                                                                                                                                    
    get: [Getter],                                                                                                                                                                         
    getChord: [Getter],                                                                                                                                                                    
    reduced: [Getter],                        
    steps: [Getter],                                                                         
    tokenize: [Getter],                                                                      
    transpose: [Getter]                                                                      
  }                                           
}

so somehow module.exports isn't exposed directly anymore?

If anyone has any idea how this might be happening, it would be much appreciated!

@lheckemann please open an issue to github.com/nodejs/merve

nodejs/merve#49

CreateString() and Parse() in node_cjs_lexer.cc unconditionally called ToLocalChecked() on the results of String::NewFromOneByte(), String::NewFromUtf8() and Set::Add(). If string or handle allocation fails or an exception is pending on the isolate, these return an empty MaybeLocal and ToLocalChecked() aborts the process with "FATAL ERROR: v8::ToLocalChecked Empty MaybeLocal". Since Parse() is on the hot path of every ESM import of a CJS module (cjsPreparseModuleExports), propagate the failure as a regular pending JavaScript exception instead so callers can recover. Fixes: nodejs#63323 Refs: nodejs#61456 Signed-off-by: Yagiz Nizipli <yagiz@nizipli.com>

CreateString() and Parse() in node_cjs_lexer.cc unconditionally called ToLocalChecked() on the results of String::NewFromOneByte(), String::NewFromUtf8() and Set::Add(). If string or handle allocation fails or an exception is pending on the isolate, these return an empty MaybeLocal and ToLocalChecked() aborts the process with "FATAL ERROR: v8::ToLocalChecked Empty MaybeLocal". Since Parse() is on the hot path of every ESM import of a CJS module (cjsPreparseModuleExports), propagate the failure as a regular pending JavaScript exception instead so callers can recover. Fixes: #63323 Refs: #61456 Signed-off-by: Yagiz Nizipli <yagiz@nizipli.com> PR-URL: #63885 Reviewed-By: Filip Skokan <panva.ip@gmail.com> Reviewed-By: Matteo Collina <matteo.collina@gmail.com> Reviewed-By: René <contact.9a5d6388@renegade334.me.uk> Reviewed-By: Anna Henningsen <anna@addaleax.net>

nodejs-github-bot added build Issues and PRs related to build files or the CI. dependencies Pull requests that update a dependency file. needs-ci PRs that need a full CI run. labels Jan 20, 2026

anonrig force-pushed the yagiz/experiment-with-cjs-lexer branch 3 times, most recently from ae6ab98 to 5e69495 Compare January 21, 2026 16:24

anonrig force-pushed the yagiz/experiment-with-cjs-lexer branch 13 times, most recently from 9bfb358 to 1da16dd Compare January 21, 2026 19:44

anonrig changed the title [DO NOT MERGE] experiment with commonjs-lexer build,deps: replace cjs-module-lexer with merve Jan 21, 2026

anonrig requested a review from guybedford January 21, 2026 19:46

anonrig force-pushed the yagiz/experiment-with-cjs-lexer branch 5 times, most recently from 66e99b4 to d687c0a Compare January 21, 2026 20:29

anonrig requested a review from mcollina January 21, 2026 20:56

Hajime-san mentioned this pull request Feb 14, 2026

fix: detect bound require reexports in cjs analysis denoland/deno_ast#328

Merged

github-actions Bot mentioned this pull request Feb 22, 2026

2026-02-24, Version 24.14.0 'Krypton' (LTS) #61924

Merged

aduh95 pushed a commit that referenced this pull request Feb 22, 2026

build,deps: replace cjs-module-lexer with merve

68da144

PR-URL: #61456 Reviewed-By: Guy Bedford <guybedford@gmail.com> Reviewed-By: Daniel Lemire <daniel@lemire.me> Reviewed-By: Richard Lau <richard.lau@ibm.com>

codebytere mentioned this pull request Feb 25, 2026

build: fix GN for new merve dep #61984

Merged

codebytere added a commit to electron/electron that referenced this pull request Feb 25, 2026

build,deps: replace cjs-module-lexer with merve

2d5fb12

nodejs/node#61456

codebytere added a commit to electron/electron that referenced this pull request Feb 26, 2026

build,deps: replace cjs-module-lexer with merve

5e45bfd

nodejs/node#61456

codebytere added a commit to electron/electron that referenced this pull request Mar 2, 2026

build,deps: replace cjs-module-lexer with merve

93bfd6b

nodejs/node#61456

EgoziE mentioned this pull request Mar 11, 2026

SIGSEGV when ESM import() loads large CJS webpack bundle (merve regression in v24.14.0) #62212

Closed

makimaki mentioned this pull request May 15, 2026

Crash in cjs_lexer::Parse since v24.14.0: FATAL ERROR: v8::ToLocalChecked Empty MaybeLocal #63323

Closed

anonrig mentioned this pull request Jun 13, 2026

src: handle empty MaybeLocal in cjs_lexer::Parse #63885

Merged

mcollina mentioned this pull request Jul 19, 2026

ci: make runtime matrix resilient to one-off flaky failures platformatic/platformatic#4977

Merged

build,deps: replace cjs-module-lexer with merve by anonrig · Pull Request #61456 · nodejs/node · GitHub

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build,deps: replace cjs-module-lexer with merve#61456nodejs-github-bot merged 2 commits intonodejs:mainnodejs/node:mainfrom anonrig:yagiz/experiment-with-cjs-lexeranonrig/node:yagiz/experiment-with-cjs-lexerCopy head branch name to clipboard

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