feat(rolldown): add isRolldownMagicString property for reliable native detection by IWANABETHATGUY · Pull Request #8614 · rolldown/rolldown

IWANABETHATGUY · 2026-03-10T04:34:46Z

Summary

External packages like rolldown-string need to detect native BindingMagicString instances, but the existing obj.constructor.name check breaks under minification or bundling. This PR adds a reliable isRolldownMagicString boolean property to the BindingMagicString prototype via Object.defineProperty (non-writable, non-configurable). A new binding-magic-string.ts module centralizes the patching and re-exports the class with proper TypeScript typings. All internal imports now go through this module to ensure consistency. Tests cover prototype presence, instance access, and detection without importing rolldown.

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Copilot

Pull request overview

This PR adds Symbol.toStringTag = 'BindingMagicString' to the BindingMagicString prototype, enabling external packages to reliably detect native instances via obj[Symbol.toStringTag] === 'BindingMagicString' instead of the fragile constructor.name check.

Changes:

Introduces a new binding-magic-string.ts wrapper module that imports BindingMagicString from binding.cjs, patches its prototype with Symbol.toStringTag, and re-exports it.
Updates all runtime (non-type-only) imports of BindingMagicString to use the new wrapper module instead of binding.cjs directly.
Adds comprehensive tests verifying the Symbol.toStringTag behavior on prototypes, instances, and via Object.prototype.toString.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
`packages/rolldown/src/binding-magic-string.ts`	New wrapper module that patches `BindingMagicString.prototype[Symbol.toStringTag]` and re-exports the class
`packages/rolldown/src/index.ts`	Updates public export to use the patched wrapper module
`packages/rolldown/src/plugin/bindingify-build-hooks.ts`	Updates runtime import to use the patched wrapper module
`packages/rolldown/src/plugin/bindingify-output-hooks.ts`	Updates runtime import to use the patched wrapper module
`packages/rolldown/tests/magic-string/magic-string-to-string-tag.test.ts`	New test file verifying `Symbol.toStringTag` behavior

IWANABETHATGUY · 2026-03-10T05:03:08Z

Merge activity

Mar 10, 5:03 AM UTC: The merge label 'graphite: merge-when-ready' was detected. This PR will be added to the Graphite merge queue once it meets the requirements.
Mar 10, 2:54 PM UTC: IWANABETHATGUY added this pull request to the Graphite merge queue.
Mar 10, 3:00 PM UTC: Merged by the Graphite merge queue.

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Pull request overview

Copilot reviewed 7 out of 7 changed files in this pull request and generated no new comments.

packages/rolldown/tests/magic-string/magic-string-to-string-tag.test.ts

Copilot

Pull request overview

Copilot reviewed 7 out of 7 changed files in this pull request and generated 1 comment.

packages/rolldown/src/binding-magic-string.ts

hyf0

FYI: Your commits are not verified.

Sorry about the question tone, I talked to CC too much and got used to ask questions.

packages/rolldown/src/binding-magic-string.ts

packages/rolldown/tests/magic-string/magic-string-to-string-tag.test.ts

…e detection (#8614) ## Summary External packages like `rolldown-string` need to detect native `BindingMagicString` instances, but the existing `obj.constructor.name` check breaks under minification or bundling. This PR adds a reliable `isRolldownMagicString` boolean property to the `BindingMagicString` prototype via `Object.defineProperty` (non-writable, non-configurable). A new `binding-magic-string.ts` module centralizes the patching and re-exports the class with proper TypeScript typings. All internal imports now go through this module to ensure consistency. Tests cover prototype presence, instance access, and detection without importing rolldown. ## Related #7522 🤖 Generated with [Claude Code](https://claude.com/claude-code)

IWANABETHATGUY · 2026-03-10T15:00:05Z

FYI: Your commits are not verified.
Sorry about the question tone, I talked to CC too much and got used to ask questions.

This is because I sent a PR with a laptop that is not used often; the key is stale. will fix it

IWANABETHATGUY · 2026-03-10T15:05:15Z

FYI: Your commits are not verified. Sorry about the question tone, I talked to CC too much and got used to ask questions.

This is because I sent a PR with a laptop that is not used often; the key is stale. will fix it

There is a pro of graphite, it would auto-sign the commit when it is merged into the main branch .

…8626) from #8614 (comment) ## Summary Rename the exported `BindingMagicString` class to `RolldownMagicString` in the public API. Only the exported name is changed — internal TypeScript code continues to use `BindingMagicString` to keep naming consistent with the binding layer. The public rename aligns the class name with its detection flag `isRolldownMagicString` (introduced in #8614). ## Changes - Update the re-export in `packages/rolldown/src/index.ts` - Update test imports to use the new name

@IWANABETHATGUY

## [1.0.0-rc.9] - 2026-03-11 ### 💥 BREAKING CHANGES - rename exported BindingMagicString to RolldownMagicString (#8626) by @IWANABETHATGUY ### 🚀 Features - rolldown: add isRolldownMagicString property for reliable native detection (#8614) by @IWANABETHATGUY - cli: align object type with rollup (#8598) by @h-a-n-a ### 🐛 Bug Fixes - rust: circular inter-chunk imports when external dynamic imports exist (#8596) by @Dunqing - update minify default docs from `false` to `'dce-only'` (#8620) by @shulaoda ### 💼 Other - fix early exit in script build-node (#8617) by @h-a-n-a ### 🚜 Refactor - binding: remove outdated TODO comment in MagicString to_string() (#8613) by @IWANABETHATGUY ### 📚 Documentation - add viteplus alpha announcement banner (#8615) by @mdong1909 - update VitePress theme to 4.8.2 for narrow-screen layout regression (#8612) by @Copilot ### ⚡ Performance - merge 4 integration test binaries into 1 (#8610) by @Boshen ### 🧪 Testing - replace heavy filename_with_hash test with targeted hash fixtures (#8597) by @Boshen ### ⚙️ Miscellaneous Tasks - ci: remove redundant `--no-run` build step from cargo-test (#8623) by @Boshen - rust: use `cargo-shear` to toggle Cargo.toml [lib] test = bool (#8622) by @Boshen - deps: update test262 submodule for tests (#8611) by @sapphi-red - skip macOS CI jobs on pull requests (#8608) by @Copilot - add rust cache to repo validation job (#8607) by @Boshen - skip running empty bin test targets (#8605) by @Boshen - skip building examples in cargo-test to reduce build time (#8603) by @Boshen - switch plain workflow checkouts to taiki-e action (#8601) by @Boshen - skip Windows CI jobs on PRs (#8600) by @Boshen - remove unused asset module (#8594) by @shulaoda ### ◀️ Revert - "docs: add viteplus alpha announcement banner (#8615)" (#8616) by @shulaoda Co-authored-by: shulaoda <165626830+shulaoda@users.noreply.github.com>

github-actions bot assigned IWANABETHATGUY Mar 10, 2026

IWANABETHATGUY changed the title ~~feat: magic string constructor toString tag~~ feat: add Symbol.toStringTag to BindingMagicString Mar 10, 2026

IWANABETHATGUY marked this pull request as ready for review March 10, 2026 04:38

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IWANABETHATGUY marked this pull request as draft March 10, 2026 04:46

IWANABETHATGUY force-pushed the 03-10-feat_magicstring_tostringtag branch from c85fbb4 to 024f0d9 Compare March 10, 2026 04:56

IWANABETHATGUY marked this pull request as ready for review March 10, 2026 05:03

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IWANABETHATGUY added the graphite: merge-when-ready label Mar 10, 2026

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IWANABETHATGUY force-pushed the 03-10-feat_magicstring_tostringtag branch from 024f0d9 to afeba2f Compare March 10, 2026 05:41

IWANABETHATGUY marked this pull request as draft March 10, 2026 05:49

IWANABETHATGUY force-pushed the 03-10-feat_magicstring_tostringtag branch from afeba2f to 0c5522e Compare March 10, 2026 07:46

IWANABETHATGUY marked this pull request as ready for review March 10, 2026 07:55

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IWANABETHATGUY force-pushed the 03-10-feat_magicstring_tostringtag branch from 82ddb03 to 6ac16a2 Compare March 10, 2026 07:59

IWANABETHATGUY changed the title ~~feat: add Symbol.toStringTag to BindingMagicString~~ feat(rolldown): add isRolldownMagicString property for reliable native detection Mar 10, 2026

IWANABETHATGUY mentioned this pull request Mar 10, 2026

Native Magic String Support #7522

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IWANABETHATGUY requested a review from hyf0 March 10, 2026 09:14

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graphite-app bot force-pushed the 03-10-feat_magicstring_tostringtag branch from 6ac16a2 to b08184e Compare March 10, 2026 14:55

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graphite-app bot merged commit b08184e into main Mar 10, 2026
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IWANABETHATGUY mentioned this pull request Mar 10, 2026

refactor!: rename exported BindingMagicString to RolldownMagicString #8626

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release: v1.0.0-rc.9 #8629

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release: v1.0.0-rc.9 #8638

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feat(rolldown): add isRolldownMagicString property for reliable native detection#8614

feat(rolldown): add isRolldownMagicString property for reliable native detection#8614
graphite-app[bot] merged 1 commit intomainfrom
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