feat: nativeMagicString `slice` by IWANABETHATGUY · Pull Request #7807 · rolldown/rolldown

IWANABETHATGUY · 2026-01-08T12:33:50Z

No description provided.

IWANABETHATGUY · 2026-01-08T12:34:11Z

feat: nativeMagicString lastChar #7819
feat: nativeMagicString snip #7818
feat: nativeMagicString construct with options #7814
feat: nativeMagicString clone #7813
feat: nativeMagicString insert #7812
feat: nativeMagicString slice #7807 👈 (View in Graphite)
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netlify · 2026-01-08T12:35:49Z

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packages/rolldown/tests/magic-string/MagicString.test.ts

Copilot

Pull request overview

This PR implements the slice method for the MagicString class, which returns the generated content between specified original character positions. The implementation adds native Rust support for this functionality that was previously unavailable.

Implements the core slice algorithm in Rust that handles character ranges, negative indices, and intro/outro content
Adds JavaScript/TypeScript bindings with proper character-to-byte index conversion for UTF-16/UTF-8 interop
Enables several slice tests while documenting specific test skips for known limitations (overlapping overwrites, move operations)

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 10 comments.

Show a summary per file

File	Description
`crates/string_wizard/src/magic_string/slice.rs`	Core Rust implementation of the slice algorithm with negative index handling and error checking for replaced characters
`crates/string_wizard/src/magic_string/mod.rs`	Adds slice module to the public API
`crates/rolldown_binding/src/types/binding_magic_string.rs`	JavaScript binding layer with character-to-byte index conversion and NAPI integration
`packages/rolldown/src/binding.d.cts`	TypeScript type definitions for the new slice method
`packages/rolldown/tests/magic-string/download-tests.mjs`	Removes slice from skipped test suites and documents specific test skips
`packages/rolldown/tests/magic-string/MagicString.test.ts`	Enables slice test suite with selective skips for complex move interactions

Comments suppressed due to low confidence (2)

packages/rolldown/tests/magic-string/MagicString.test.ts:1589

There is no test coverage for the case where start and end are equal (e.g., slice(5, 5)), which should return an empty string. Consider adding a test case to verify this edge case behaves correctly.

  describe('slice', () => {
    it.skip('should return the generated content between the specified original characters', () => {
      const s = new MagicString('abcdefghijkl');

      assert.equal(s.slice(3, 9), 'defghi');
      s.overwrite(4, 8, 'XX');
      assert.equal(s.slice(3, 9), 'dXXi');
      s.overwrite(2, 10, 'ZZ');
      assert.equal(s.slice(1, 11), 'bZZk');
      assert.equal(s.slice(2, 10), 'ZZ');

      assert.throws(() => s.slice(3, 9));
    });

    it('defaults `end` to the original string length', () => {
      const s = new MagicString('abcdefghijkl');
      assert.equal(s.slice(3), 'defghijkl');
    });

    it('allows negative numbers as arguments', () => {
      const s = new MagicString('abcdefghijkl');
      assert.equal(s.slice(-3), 'jkl');
      assert.equal(s.slice(0, -3), 'abcdefghi');
    });

    it('includes inserted characters, respecting insertion direction', () => {
      const s = new MagicString('abefij');

      s.prependRight(2, 'cd');
      s.appendLeft(4, 'gh');

      assert.equal(s.slice(), 'abcdefghij');
      assert.equal(s.slice(1, 5), 'bcdefghi');
      assert.equal(s.slice(2, 4), 'cdefgh');
      assert.equal(s.slice(3, 4), 'fgh');
      assert.equal(s.slice(0, 2), 'ab');
      assert.equal(s.slice(0, 3), 'abcde');
      assert.equal(s.slice(4, 6), 'ij');
      assert.equal(s.slice(3, 6), 'fghij');
    });

    it.skip('supports characters moved outward', () => {
      const s = new MagicString('abcdEFghIJklmn');

      s.move(4, 6, 2);
      s.move(8, 10, 12);
      assert.equal(s.toString(), 'abEFcdghklIJmn');

      assert.equal(s.slice(1, -1), 'bEFcdghklIJm');
      assert.equal(s.slice(2, -2), 'cdghkl');
      assert.equal(s.slice(3, -3), 'dghk');
      assert.equal(s.slice(4, -4), 'EFcdghklIJ');
      assert.equal(s.slice(5, -5), 'FcdghklI');
      assert.equal(s.slice(6, -6), 'gh');
    });

    it.skip('supports characters moved inward', () => {
      const s = new MagicString('abCDefghijKLmn');

      s.move(2, 4, 6);
      s.move(10, 12, 8);
      assert.equal(s.toString(), 'abefCDghKLijmn');

      assert.equal(s.slice(1, -1), 'befCDghKLijm');
      assert.equal(s.slice(2, -2), 'CDghKL');
      assert.equal(s.slice(3, -3), 'DghK');
      assert.equal(s.slice(4, -4), 'efCDghKLij');
      assert.equal(s.slice(5, -5), 'fCDghKLi');
      assert.equal(s.slice(6, -6), 'gh');
    });

    it.skip('supports characters moved opposing', () => {
      const s = new MagicString('abCDefghIJkl');

      s.move(2, 4, 8);
      s.move(8, 10, 4);
      assert.equal(s.toString(), 'abIJefghCDkl');

      assert.equal(s.slice(1, -1), 'bIJefghCDk');
      assert.equal(s.slice(2, -2), '');
      assert.equal(s.slice(3, -3), '');
      assert.equal(s.slice(-3, 3), 'JefghC');
      assert.equal(s.slice(4, -4), 'efgh');
      assert.equal(s.slice(0, 3), 'abIJefghC');
      assert.equal(s.slice(3), 'Dkl');
      assert.equal(s.slice(0, -3), 'abI');
      assert.equal(s.slice(-3), 'JefghCDkl');
    });

    it('errors if replaced characters are used as slice anchors', () => {
      const s = new MagicString('abcdef');
      s.overwrite(2, 4, 'CD');

      assert.throws(() => s.slice(2, 3), /slice end anchor/);

      assert.throws(() => s.slice(3, 4), /slice start anchor/);

      assert.throws(() => s.slice(3, 5), /slice start anchor/);

      assert.equal(s.slice(1, 5), 'bCDe');
    });

    it('does not error if slice is after removed characters', () => {
      const s = new MagicString('abcdef');

      s.remove(0, 2);

      assert.equal(s.slice(2, 4), 'cd');
    });
  });

packages/rolldown/tests/magic-string/MagicString.test.ts:1589

There is no test coverage for the case where both start and end are negative and result in an empty range (e.g., slice(-3, -5) which has start > end after normalization). Consider adding a test case to verify this edge case returns an empty string as expected.

  describe('slice', () => {
    it.skip('should return the generated content between the specified original characters', () => {
      const s = new MagicString('abcdefghijkl');

      assert.equal(s.slice(3, 9), 'defghi');
      s.overwrite(4, 8, 'XX');
      assert.equal(s.slice(3, 9), 'dXXi');
      s.overwrite(2, 10, 'ZZ');
      assert.equal(s.slice(1, 11), 'bZZk');
      assert.equal(s.slice(2, 10), 'ZZ');

      assert.throws(() => s.slice(3, 9));
    });

    it('defaults `end` to the original string length', () => {
      const s = new MagicString('abcdefghijkl');
      assert.equal(s.slice(3), 'defghijkl');
    });

    it('allows negative numbers as arguments', () => {
      const s = new MagicString('abcdefghijkl');
      assert.equal(s.slice(-3), 'jkl');
      assert.equal(s.slice(0, -3), 'abcdefghi');
    });

    it('includes inserted characters, respecting insertion direction', () => {
      const s = new MagicString('abefij');

      s.prependRight(2, 'cd');
      s.appendLeft(4, 'gh');

      assert.equal(s.slice(), 'abcdefghij');
      assert.equal(s.slice(1, 5), 'bcdefghi');
      assert.equal(s.slice(2, 4), 'cdefgh');
      assert.equal(s.slice(3, 4), 'fgh');
      assert.equal(s.slice(0, 2), 'ab');
      assert.equal(s.slice(0, 3), 'abcde');
      assert.equal(s.slice(4, 6), 'ij');
      assert.equal(s.slice(3, 6), 'fghij');
    });

    it.skip('supports characters moved outward', () => {
      const s = new MagicString('abcdEFghIJklmn');

      s.move(4, 6, 2);
      s.move(8, 10, 12);
      assert.equal(s.toString(), 'abEFcdghklIJmn');

      assert.equal(s.slice(1, -1), 'bEFcdghklIJm');
      assert.equal(s.slice(2, -2), 'cdghkl');
      assert.equal(s.slice(3, -3), 'dghk');
      assert.equal(s.slice(4, -4), 'EFcdghklIJ');
      assert.equal(s.slice(5, -5), 'FcdghklI');
      assert.equal(s.slice(6, -6), 'gh');
    });

    it.skip('supports characters moved inward', () => {
      const s = new MagicString('abCDefghijKLmn');

      s.move(2, 4, 6);
      s.move(10, 12, 8);
      assert.equal(s.toString(), 'abefCDghKLijmn');

      assert.equal(s.slice(1, -1), 'befCDghKLijm');
      assert.equal(s.slice(2, -2), 'CDghKL');
      assert.equal(s.slice(3, -3), 'DghK');
      assert.equal(s.slice(4, -4), 'efCDghKLij');
      assert.equal(s.slice(5, -5), 'fCDghKLi');
      assert.equal(s.slice(6, -6), 'gh');
    });

    it.skip('supports characters moved opposing', () => {
      const s = new MagicString('abCDefghIJkl');

      s.move(2, 4, 8);
      s.move(8, 10, 4);
      assert.equal(s.toString(), 'abIJefghCDkl');

      assert.equal(s.slice(1, -1), 'bIJefghCDk');
      assert.equal(s.slice(2, -2), '');
      assert.equal(s.slice(3, -3), '');
      assert.equal(s.slice(-3, 3), 'JefghC');
      assert.equal(s.slice(4, -4), 'efgh');
      assert.equal(s.slice(0, 3), 'abIJefghC');
      assert.equal(s.slice(3), 'Dkl');
      assert.equal(s.slice(0, -3), 'abI');
      assert.equal(s.slice(-3), 'JefghCDkl');
    });

    it('errors if replaced characters are used as slice anchors', () => {
      const s = new MagicString('abcdef');
      s.overwrite(2, 4, 'CD');

      assert.throws(() => s.slice(2, 3), /slice end anchor/);

      assert.throws(() => s.slice(3, 4), /slice start anchor/);

      assert.throws(() => s.slice(3, 5), /slice start anchor/);

      assert.equal(s.slice(1, 5), 'bCDe');
    });

    it('does not error if slice is after removed characters', () => {
      const s = new MagicString('abcdef');

      s.remove(0, 2);

      assert.equal(s.slice(2, 4), 'cd');
    });
  });

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crates/string_wizard/src/magic_string/slice.rs

crates/rolldown_binding/src/types/binding_magic_string.rs

crates/string_wizard/src/magic_string/slice.rs

github-actions · 2026-01-09T07:35:32Z

Benchmarks Rust

target: main(7d70b52)
pr: 01-08-feat_nativemagicstring_slice(1960898)

group                                                        pr                                     target
-----                                                        --                                     ------
bundle/bundle@multi-duplicated-top-level-symbol              1.00     68.6±2.28ms        ? ?/sec    1.05     72.4±1.80ms        ? ?/sec
bundle/bundle@multi-duplicated-top-level-symbol-sourcemap    1.00     74.7±2.09ms        ? ?/sec    1.01     75.6±2.50ms        ? ?/sec
bundle/bundle@rome_ts                                        1.01    110.3±2.41ms        ? ?/sec    1.00    109.3±2.38ms        ? ?/sec
bundle/bundle@rome_ts-sourcemap                              1.00    121.6±3.38ms        ? ?/sec    1.01    122.4±1.78ms        ? ?/sec
bundle/bundle@threejs                                        1.03     40.2±1.56ms        ? ?/sec    1.00     39.2±0.85ms        ? ?/sec
bundle/bundle@threejs-sourcemap                              1.02     45.7±0.96ms        ? ?/sec    1.00     44.7±0.75ms        ? ?/sec
bundle/bundle@threejs10x                                     1.01    396.8±5.02ms        ? ?/sec    1.00    394.4±7.93ms        ? ?/sec
bundle/bundle@threejs10x-sourcemap                           1.00    458.2±5.09ms        ? ?/sec    1.00    458.0±8.28ms        ? ?/sec
scan/scan@rome_ts                                            1.00     87.5±2.47ms        ? ?/sec    1.00     87.6±1.84ms        ? ?/sec
scan/scan@threejs                                            1.02     29.6±0.60ms        ? ?/sec    1.00     28.9±0.59ms        ? ?/sec
scan/scan@threejs10x                                         1.00    299.9±4.96ms        ? ?/sec    1.00    299.7±5.80ms        ? ?/sec

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Pull request overview

Copilot reviewed 6 out of 6 changed files in this pull request and generated no new comments.

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crates/rolldown_binding/src/types/binding_magic_string.rs

Rewrites the `slice` method in `string_wizard` to be a faithful 1:1 port of the original JavaScript magic-string implementation (lines 598-650). Key changes: - Match the exact loop structure: find start chunk first, then iterate - Intro handling: include if not start chunk OR chunk.start == start - Content slicing: use same calculation as JS for sliceStart/sliceEnd - Outro handling: include if !containsEnd OR chunk.end == end - Error messages match JS format with period at end Also enables two previously skipped tests in MagicString.test.ts.

graphite-app · 2026-01-09T08:29:29Z

Merge activity

Jan 9, 8:29 AM UTC: IWANABETHATGUY added this pull request to the Graphite merge queue.

@shulaoda

## [1.0.0-beta.60] - 2026-01-14 ### 💥 BREAKING CHANGES - tsconfig: enable auto-discovery by default (#7817) by @shulaoda ### 🚀 Features - distinguish transformer diagnostics from parse errors (#7872) by @shulaoda - emit transformer warnings instead of ignoring them (#7850) by @shulaoda - node: add `output.codeSplitting` option and deprecate `output.advancedChunks` (#7855) by @hyf0 - nativeMagicString reset (#7828) by @IWANABETHATGUY - nativeMagicString lastChar (#7819) by @IWANABETHATGUY - dev/lazy: inject lazy compilation runtime automatically (#7816) by @hyf0 - nativeMagicString snip (#7818) by @IWANABETHATGUY - nativeMagicString construct with options (#7814) by @IWANABETHATGUY - nativeMagicString clone (#7813) by @IWANABETHATGUY - nativeMagicString `insert` (#7812) by @IWANABETHATGUY - nativeMagicString `slice` (#7807) by @IWANABETHATGUY - nativeMagicString trim methods (#7800) by @IWANABETHATGUY - make closeBundle hook receive the last error (#7278) by @Copilot ### 🐛 Bug Fixes - when package only contains export default, cjsDefault didn't resolve correctly (#7873) by @IWANABETHATGUY - inline __name calls for default exports (#7862) by @IWANABETHATGUY - improve variable renaming to avoid unnecessary shadowing in nested scopes (#7859) by @IWANABETHATGUY - use correct index when inserting keepNames statements during export default transformation (#7853) by @IWANABETHATGUY - transform non-static dynamic imports when `dynamicImportInCjs` is `false` (#7823) by @shulaoda - dev/lazy: should include imported and non-executed modules in the patch (#7815) by @hyf0 - set ExportsKind to Esm when json is none object literal (#7808) by @IWANABETHATGUY - nativeMagicString move api (#7796) by @IWANABETHATGUY - remove unnecessary exports after merging into commong and user defined entry (#7789) by @IWANABETHATGUY - use output.name instead of chunk.name in mixed export warning (#7788) by @Copilot ### 🚜 Refactor - generalize ParseError to OxcError with dynamic EventKind (#7868) by @shulaoda - rust: rename `advanced_chunks` to `manual_code_splitting` (#7856) by @hyf0 - string_wizard error hanlding (#7830) by @IWANABETHATGUY - remove `experimental.disableLiveBindings` option (#7820) by @sapphi-red - node/test: run fixture tests in concurrent (#7790) by @hyf0 - move ConfigExport and RolldownOptionsFunction types to define-config (#7799) by @shulaoda - cli: validate config after resolving and improve error message (#7798) by @shulaoda ### 📚 Documentation - rebrand (#7670) by @yyx990803 - fix incorrect default value for propertyReadSideEffects (#7847) by @Copilot - remove options pages and redirect to reference pages (#7834) by @sapphi-red - options: inline types to option property pages (#7831) by @sapphi-red - options: port checks.pluginTimings content from options page to reference page (#7832) by @sapphi-red - options: use `@linkcode` where possible (#7824) by @sapphi-red - options: port content from options page to reference page (#7822) by @sapphi-red - options: add descriptions for output options (#7821) by @sapphi-red - options: add description for input options (#7802) by @sapphi-red - options: add description for `checks.*` (#7801) by @sapphi-red - apis: add hook graph (#7671) by @sapphi-red ### 🧪 Testing - add all valid combination of chunk exports related test (#7851) by @IWANABETHATGUY - enable MagicString test after api return type alignment (#7797) by @IWANABETHATGUY - init magic-string test (#7794) by @IWANABETHATGUY ### ⚙️ Miscellaneous Tasks - vite-tests: configure git user for rebase operation (#7875) by @shulaoda - rolldown_binding: remove v3 native plugins (#7837) by @shulaoda - rolldown_binding: allow crate-type as lib (#7866) by @Brooooooklyn - README.md: adjust position and size of rolldown logo (#7861) by @hyf0 - deps: update test262 submodule for tests (#7857) by @sapphi-red - deps: update oxc to v0.108.0 (#7845) by @renovate[bot] - deps: update dependency oxlint to v1.39.0 (#7849) by @renovate[bot] - deps: update dependency oxfmt to ^0.24.0 (#7844) by @renovate[bot] - deps: update npm packages (#7841) by @renovate[bot] - deps: update rust crates (#7839) by @renovate[bot] - deps: update github-actions (#7840) by @renovate[bot] - use workspace edition for all crates (#7829) by @IWANABETHATGUY - deps: update dependency oxlint-tsgolint to v0.11.0 (#7827) by @renovate[bot] - deps: update napi to v3.8.2 (#7810) by @renovate[bot] - remove outdated snapshot files (#7806) by @shulaoda - deps: update crate-ci/typos action to v1.42.0 (#7792) by @renovate[bot] Co-authored-by: shulaoda <[email protected]>

github-actions bot assigned IWANABETHATGUY Jan 8, 2026

IWANABETHATGUY force-pushed the 01-08-feat_nativemagicstring_slice branch from 4874141 to 8d38e99 Compare January 9, 2026 06:47

IWANABETHATGUY commented Jan 9, 2026

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IWANABETHATGUY force-pushed the 01-08-feat_nativemagicstring_slice branch from e5b2103 to 25f65a4 Compare January 9, 2026 06:59

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feat: nativeMagicString insert #7812

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IWANABETHATGUY changed the title ~~feat: nativeMagicString slice~~ feat: nativeMagicString slice Jan 9, 2026

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feat: nativeMagicString clone #7813

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crates/rolldown_binding/src/types/binding_magic_string.rs Outdated Show resolved Hide resolved

IWANABETHATGUY force-pushed the 01-08-feat_nativemagicstring_slice branch from bac73ef to 1960898 Compare January 9, 2026 08:11

IWANABETHATGUY mentioned this pull request Jan 9, 2026

feat: nativeMagicString construct with options #7814

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IWANABETHATGUY merged commit b20fec4 into main Jan 9, 2026
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IWANABETHATGUY deleted the 01-08-feat_nativemagicstring_slice branch January 9, 2026 08:29

IWANABETHATGUY mentioned this pull request Jan 9, 2026

feat: nativeMagicString snip #7818

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IWANABETHATGUY mentioned this pull request Jan 9, 2026

feat: nativeMagicString lastChar #7819

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This was referenced Jan 14, 2026

release: v1.0.0-beta.60 #7869

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release: v1.0.0-beta.60 #7877

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sapphi-red mentioned this pull request Feb 14, 2026

Native Magic String Support #7522

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