refactor(webpack-cli): replace fastest-levenshtein with in-tree implementation by alexander-akait · Pull Request #4762 · webpack/webpack-cli

alexander-akait · 2026-05-27T13:39:28Z

Drop the fastest-levenshtein dependency in favor of a small in-tree
Levenshtein distance (Myers' bit-parallel algorithm, inspired by
fastest-levenshtein) used for command/option "did you mean" suggestions,
and add unit tests for it.

https://claude.ai/code/session_013zogbY9uURTCwhdRrifVBt

…mentation Drop the fastest-levenshtein dependency in favor of a small in-tree Levenshtein distance (Myers' bit-parallel algorithm, inspired by fastest-levenshtein) used for command/option "did you mean" suggestions, and add unit tests for it. https://claude.ai/code/session_013zogbY9uURTCwhdRrifVBt

changeset-bot · 2026-05-27T13:39:34Z

🦋 Changeset detected

Latest commit: c4200f2

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
webpack-cli	Patch

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linux-foundation-easycla · 2026-05-27T13:39:36Z

❌ - login: @claude / name: Claude. The commit (74caa91, c4200f2) is not authorized under a signed CLA. Please click here to be authorized. For further assistance with EasyCLA, please visit our EasyCLA portal and chat with our support bot.

codecov · 2026-05-27T13:41:48Z

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.82%. Comparing base (183d0e6) to head (c4200f2).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4762      +/-   ##
==========================================
+ Coverage   92.58%   92.82%   +0.24%     
==========================================
  Files          14       15       +1     
  Lines        4911     5076     +165     
  Branches      731      752      +21     
==========================================
+ Hits         4547     4712     +165     
  Misses        362      362              
  Partials        2        2

Files with missing lines	Coverage Δ
packages/webpack-cli/src/levenshtein.ts	`100.00% <100.00%> (ø)`
packages/webpack-cli/src/webpack-cli.ts	`96.18% <100.00%> (ø)`

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Copilot

Pull request overview

This PR removes the fastest-levenshtein dependency from webpack-cli and replaces it with an in-tree Levenshtein distance implementation (Myers’ bit-parallel algorithm) to power “did you mean” suggestions, along with unit tests.

Changes:

Added an in-tree distance() implementation in packages/webpack-cli/src/levenshtein.ts and switched webpack-cli to use it.
Removed fastest-levenshtein from packages/webpack-cli/package.json and package-lock.json.
Added Jest tests for the new distance implementation and a changeset entry documenting the patch change.

Reviewed changes

Copilot reviewed 5 out of 6 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
`test/api/levenshtein.test.js`	Adds unit tests for the new in-tree Levenshtein `distance()` helper.
`packages/webpack-cli/src/webpack-cli.ts`	Replaces the external `fastest-levenshtein` import with the new in-tree implementation.
`packages/webpack-cli/src/levenshtein.ts`	Introduces the Myers bit-parallel Levenshtein implementation used for suggestions.
`packages/webpack-cli/package.json`	Drops `fastest-levenshtein` from dependencies.
`package-lock.json`	Removes the `fastest-levenshtein` lockfile entries.
`.changeset/replace-fastest-levenshtein.md`	Records the dependency replacement as a patch-level change.

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alexander-akait · 2026-05-27T13:48:12Z

+      peq[b.charCodeAt(k)] |= 1 << k;
+    }
+
+    for (let i = 0; i < n; i++) {
+      const eq = peq[a.charCodeAt(i)];
+      const pb = (phc[(i / 32) | 0] >>> i) & 1;
+      const mb = (mhc[(i / 32) | 0] >>> i) & 1;
+      const xv = eq | mv;
+      const xh = ((((eq | mb) & pv) + pv) ^ pv) | eq | mb;
+      let ph = mv | ~(xh | pv);
+      let mh = pv & xh;
+
+      if ((ph >>> 31) ^ pb) {
+        phc[(i / 32) | 0] ^= 1 << i;
+      }
+
+      if ((mh >>> 31) ^ mb) {
+        mhc[(i / 32) | 0] ^= 1 << i;


Leaving this as-is: the word is already selected explicitly via (i / 32) | 0, and the within-word shift intentionally relies on JS's standard mask-to-31 semantics. This is a faithful port of the upstream fastest-levenshtein algorithm, verified bit-for-bit against it (including a 2000-case fuzz across the myersX paths), so I'd prefer not to rewrite the hot loop and risk diverging from the reference. The parameter-naming and long-vs-short-test suggestions are addressed in c4200f2.

Generated by Claude Code

+function myersX(b: string, a: string): number {
+  const n = a.length;
+  const m = b.length;
+  const mhc: number[] = [];
+  const phc: number[] = [];
+  const horizontalSize = Math.ceil(n / 32);
+  const verticalSize = Math.ceil(m / 32);


+    const b = `${"a".repeat(39)}b`;
+
+    expect(distance(a, b)).toBe(1);
+    expect(distance("a".repeat(40), "b".repeat(40))).toBe(40);


…case Address review feedback: rename the swapped myersX parameters to longer/shorter so they match their internal usage, and add a regression test for a long string against a much shorter one (40 vs 5). https://claude.ai/code/session_013zogbY9uURTCwhdRrifVBt

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Pull request overview

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Copilot AI review requested due to automatic review settings May 27, 2026 13:39

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alexander-akait merged commit 2bbb639 into main May 27, 2026
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alexander-akait deleted the claude/replace-fastest-levenshtein-Tkvl9 branch May 27, 2026 13:59

github-actions Bot mentioned this pull request May 27, 2026

chore(release): new release #4711

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refactor(webpack-cli): replace fastest-levenshtein with in-tree implementation#4762

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