### What does this PR do?
### How did you verify your code works?
---------
Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>
Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: Claude Bot <claude-bot@bun.sh>
Co-authored-by: claude[bot] <209825114+claude[bot]@users.noreply.github.com>
## Summary
- Adds `Bun.JSON5.parse()` and `Bun.JSON5.stringify()` as built-in APIs
- Adds `.json5` file support in the module resolver and bundler
- Parser uses a scanner/parser split architecture with a labeled switch
pattern (like the YAML parser) — the scanner produces typed tokens, the
parser never touches source bytes directly
- 430+ tests covering the official JSON5 test suite, escape sequences,
numbers, comments, whitespace (including all Unicode whitespace types),
unquoted/reserved-word keys, unicode identifiers, deeply nested
structures, garbage input, error messages, and stringify behavior
<img width="659" height="610" alt="Screenshot 2026-01-25 at 12 19 57 AM"
src="https://github.com/user-attachments/assets/e300125a-f197-4cad-90ed-e867b6232a01"
/>
## Test plan
- [x] `bun bd test test/js/bun/json5/json5.test.ts` — 317 tests
- [x] `bun bd test test/js/bun/json5/json5-test-suite.test.ts` — 113
tests from the official JSON5 test suite
- [x] `bun bd test test/js/bun/resolve/json5/json5.test.js` — .json5
module resolution
closes#3175🤖 Generated with [Claude Code](https://claude.com/claude-code)
---------
Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>
## Summary
- Fix missing semicolons in minified output when using both default and
named imports from `"bun"` module
- The issue occurred in `printInternalBunImport` when transitioning
between star_name, default_name, and items sections without flushing
pending semicolons
## Test plan
- Added regression tests in `test/regression/issue/26371.test.ts`
covering:
- Default + named imports (`import bun, { embeddedFiles } from "bun"`)
- Namespace + named imports (`import * as bun from "bun"; import {
embeddedFiles } from "bun"`)
- Namespace + default + named imports combination
- Verified test fails with `USE_SYSTEM_BUN=1` (reproduces bug)
- Verified test passes with `bun bd test` (fix works)
Fixes#26371🤖 Generated with [Claude Code](https://claude.com/claude-code)
---------
Co-authored-by: Claude Bot <claude-bot@bun.sh>
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
### What does this PR do?
Fixes#5344Fixes#6356
### How did you verify your code works?
Some test coverage
---------
Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: Claude Bot <claude-bot@bun.sh>
## Summary
- Adds `import { feature } from "bun:bundle"` for compile-time feature
flag checking
- `feature("FLAG_NAME")` calls are replaced with `true`/`false` at
bundle time
- Enables dead-code elimination through `--feature=FLAG_NAME` CLI
argument
- Works in `bun build`, `bun run`, and `bun test`
- Available in both CLI and `Bun.build()` JavaScript API
## Usage
```ts
import { feature } from "bun:bundle";
if (feature("SUPER_SECRET")) {
console.log("Secret feature enabled!");
} else {
console.log("Normal mode");
}
```
### CLI
```bash
# Enable feature during build
bun build --feature=SUPER_SECRET index.ts
# Enable at runtime
bun run --feature=SUPER_SECRET index.ts
# Enable in tests
bun test --feature=SUPER_SECRET
```
### JavaScript API
```ts
await Bun.build({
entrypoints: ['./index.ts'],
outdir: './out',
features: ['SUPER_SECRET', 'ANOTHER_FLAG'],
});
```
## Implementation
- Added `bundler_feature_flags` (as `*const bun.StringSet`) to
`RuntimeFeatures` and `BundleOptions`
- Added `bundler_feature_flag_ref` to Parser struct to track the
`feature` import
- Handle `bun:bundle` import at parse time (similar to macros) - capture
ref, return empty statement
- Handle `feature()` calls in `e_call` visitor - replace with boolean
based on flags
- Wire feature flags through CLI arguments and `Bun.build()` API to
bundler options
- Added `features` option to `JSBundler.zig` for JavaScript API support
- Added TypeScript types in `bun.d.ts`
- Added documentation to `docs/bundler/index.mdx`
## Test plan
- [x] Basic feature flag enabled/disabled tests (both CLI and API
backends)
- [x] Multiple feature flags test
- [x] Dead code elimination verification tests
- [x] Error handling for invalid arguments
- [x] Runtime tests with `bun run --feature=FLAG`
- [x] Test runner tests with `bun test --feature=FLAG`
- [x] Aliased import tests (`import { feature as checkFeature }`)
- [x] Ternary operator DCE tests
- [x] Tests use `itBundled` with both `backend: "cli"` and `backend:
"api"`
🤖 Generated with [Claude Code](https://claude.com/claude-code)
---------
Co-authored-by: Claude Bot <claude-bot@bun.sh>
Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>
Co-authored-by: Alistair Smith <hi@alistair.sh>
Co-authored-by: Jarred Sumner <jarred@jarredsumner.com>
### What does this PR do?
Fixes printing `import.meta.url` and others with `--bytecode`. Fixes
#14954.
Fixes printing `__toESM` when output module format is CJS and input
module format is ESM.
The key change is that `__toESM`'s `isNodeMode` parameter now depends on
the **input module type** (whether the importing file uses ESM syntax
like `import`/`export`) rather than the output format. This matches
Node.js ESM behavior where importing CommonJS from `.mjs` files always
wraps the entire `module.exports` object as the default export, ignoring
`__esModule` markers.
### How did you verify your code works?
Added comprehensive test suite in `test/bundler/bundler_cjs.test.ts`
with **23 tests** covering:
#### Core Behaviors:
- ✅ Files using `import` syntax always get `isNodeMode=1`, which
**ignores `__esModule`** markers and wraps the entire CJS module as
default
- ✅ This matches Node.js ESM semantics for importing CJS from `.mjs`
files
- ✅ Different CJS export patterns (`exports.x`, `module.exports = ...`,
functions, primitives)
- ✅ Named, default, and namespace (`import *`) imports
- ✅ Different targets (node, browser, bun) - all behave the same
- ✅ Different output formats (esm, cjs) - format doesn't affect the
behavior
- ✅ `.mjs` files re-exporting from `.cjs`
- ✅ Deep re-export chains
- ✅ Edge cases (non-boolean `__esModule`, `__esModule=false`, etc.)
#### Test Results:
- **With this PR's changes**: All 23 tests pass ✅
- **Without this PR (system bun)**: 22 pass, 1 fails (the one testing
that `__esModule` is ignored with import syntax + CJS format)
The failing test with system bun demonstrates the bug being fixed:
currently, format=cjs with import syntax still respects `__esModule`,
but it should ignore it (matching Node.js behavior).
---------
Co-authored-by: Jarred Sumner <jarred@jarredsumner.com>
Co-authored-by: Claude Bot <claude-bot@bun.sh>
### What does this PR do?
Fixes a crash related to the dev server overwriting the uws user context
pointer when setting abort callback.
Adds support for `return new Response(<jsx />, { ... })` and `return
Response.render(...)` and `return Response.redirect(...)`:
- Created a `SSRResponse` class to handle this (see
`JSBakeResponse.{h,cpp}`)
- `SSRResponse` is designed to "fake" being a React component
- This is done in JSBakeResponse::create inside of
src/bun.js/bindings/JSBakeResponse.cpp
- And `src/js/builtins/BakeSSRResponse.ts` defines a `wrapComponent`
function which wraps
the passed in component (when doing `new Response(<jsx />, ...)`). It
does
this to throw an error (in redirect()/render() case) or return the
component.
- Created a `BakeAdditionsToGlobal` struct which contains some
properties
needed for this
- Added some of the properties we need to fake to BunBuiltinNames.h
(e.g.
`$$typeof`), the rationale behind this is that we couldn't use
`structure->addPropertyTransition` because JSBakeResponse is not a final
JSObject.
- When bake and server-side, bundler rewrites `Response ->
Bun.SSRResponse` (see `src/ast/P.zig` and `src/ast/visitExpr.zig`)
- Created a new WebCore body variant (`Render: struct { path: []const u8
}`)
- Created when `return Response.render(...)`
- When handled, it re-invokes dev server to render the new path
Enables server-side sourcemaps for the dev server:
- New source providers for server-side:
(`DevServerSourceProvider.{h,cpp}`)
- IncrementalGraph and SourceMapStore are updated to support this
There are numerous other stuff:
- allow `app` configuration from Bun.serve(...)
- fix errors stopping dev server
- fix use after free related to in
RequestContext.finishRunningErrorHandler
- Request.cookies
- Make `"use client";` components work
- Fix some bugs using `require(...)` in dev server
- Fix catch-all routes not working in the dev server
- Updates `findSourceMappingURL(...)` to use `std.mem.lastIndexOf(...)`
because
the sourcemap that should be used is the last one anyway
---------
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Co-authored-by: Claude Bot <claude-bot@bun.sh>
Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: Alistair Smith <hi@alistair.sh>
## Summary
Implements the `typeof undefined === 'u'` minification optimization from
esbuild in Bun's minifier, and fixes dead code elimination (DCE) for
typeof comparisons with string literals.
### Part 1: Minification Optimization
This optimization transforms:
- `typeof x === "undefined"` → `typeof x > "u"`
- `typeof x !== "undefined"` → `typeof x < "u"`
- `typeof x == "undefined"` → `typeof x > "u"`
- `typeof x != "undefined"` → `typeof x < "u"`
Also handles flipped operands (`"undefined" === typeof x`).
### Part 2: DCE Fix for Typeof Comparisons
Fixed dead code elimination to properly handle typeof comparisons with
strings (e.g., `typeof x <= 'u'`). These patterns can now be correctly
eliminated when they reference unbound identifiers that would throw
ReferenceErrors.
## Before/After
### Minification
Before:
```javascript
console.log(typeof x === "undefined");
```
After:
```javascript
console.log(typeof x > "u");
```
### Dead Code Elimination
Before (incorrectly kept):
```javascript
var REMOVE_1 = typeof x <= 'u' ? x : null;
```
After (correctly eliminated):
```javascript
// removed
```
## Implementation
### Minification
- Added `tryOptimizeTypeofUndefined` function in
`src/ast/visitBinaryExpression.zig`
- Handles all 4 equality operators and both operand orders
- Only optimizes when both sides match the expected pattern (typeof
expression + "undefined" string)
- Replaces "undefined" with "u" and changes operators to `>` (for
equality) or `<` (for inequality)
### DCE Improvements
- Extended `isSideEffectFreeUnboundIdentifierRef` in `src/ast/P.zig` to
handle comparison operators (`<`, `>`, `<=`, `>=`)
- Added comparison operators to `simplifyUnusedExpr` in
`src/ast/SideEffects.zig`
- Now correctly identifies when typeof comparisons guard against
undefined references
## Test Plan
✅ Added comprehensive test in `test/bundler/bundler_minify.test.ts` that
verifies:
- All 8 variations work correctly (4 operators × 2 operand orders)
- Cases that shouldn't be optimized are left unchanged
- Matches esbuild's behavior exactly using inline snapshots
✅ DCE test `dce/DCETypeOfCompareStringGuardCondition` now passes:
- Correctly eliminates dead code with typeof comparison patterns
- Maintains compatibility with esbuild's DCE behavior
🤖 Generated with [Claude Code](https://claude.ai/code)
Co-Authored-By: Claude <noreply@anthropic.com>
---------
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Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>
Co-authored-by: Jarred Sumner <jarred@jarredsumner.com>
Co-authored-by: Dylan Conway <dylan.conway567@gmail.com>
in JS, `new TextDecoder("latin1").decode(...)` uses cp1252. In python,
latin1 is half-width utf-16. In our code, latin1 typically refers to
half-width utf-16 because JavaScriptCore uses that for most strings, but
sometimes it refers to cp1252. Rename the cp1252 functions to be called
cp1252
Also fixes an issue where Buffer.from with utf-16le would sometimes
output the wrong value:
```js
$> bun -p "Buffer.from('\x80', 'utf-16le')"
<Buffer ac 20>
$> node -p "Buffer.from('\x80', 'utf-16le')"
<Buffer 80 00>
$> bun-debug -p "Buffer.from('\x80', 'utf-16le')"
<Buffer 80 00>
```
Replace `catch bun.outOfMemory()`, which can accidentally catch
non-OOM-related errors, with either `bun.handleOom` or a manual `catch
|err| switch (err)`.
(For internal tracking: fixes STAB-1070)
---------
Co-authored-by: Dylan Conway <dylan.conway567@gmail.com>
### What does this PR do?
This PR adds builtin YAML parsing with `Bun.YAML.parse`
```js
import { YAML } from "bun";
const items = YAML.parse("- item1");
console.log(items); // [ "item1" ]
```
Also YAML imports work just like JSON and TOML imports
```js
import pkg from "./package.yaml"
console.log({ pkg }); // { pkg: { name: "pkg", version: "1.1.1" } }
```
### How did you verify your code works?
Added some tests for YAML imports and parsed values.
---------
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Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>
Co-authored-by: Jarred Sumner <jarred@jarredsumner.com>
* `IncrementalGraph(.client).File` packs its fields in a specific way to
save space, but it makes the struct hard to use and error-prone (e.g.,
untagged unions with tags stored in a separate `flags` struct). This PR
changes `File` to have a human-readable layout, but adds methods to
convert it to and from `File.Packed`, a packed version with the same
space efficiency as before.
* Reduce the need to pass the dev allocator to functions (e.g.,
`deinit`) by storing it as a struct field via the new `DevAllocator`
type. This type has no overhead in release builds, or when
`AllocationScope` is disabled.
* Use owned pointers in `PackedMap`.
* Use `bun.ptr.Shared` for `PackedMap` instead of the old
`bun.ptr.RefPtr`.
* Add `bun.ptr.ScopedOwned`, which is like `bun.ptr.Owned`, but can
store an `AllocationScope`. No overhead in release builds or when
`AllocationScope` is disabled.
* Reduce redundant allocators in `BundleV2`.
* Add owned pointer conversions to `MutableString`.
* Make `AllocationScope` behave like a pointer, so it can be moved
without invalidating allocations. This eliminates the need for
self-references.
* Change memory cost algorithm so it doesn't rely on “dedupe bits”.
These bits used to take advantage of padding but there is now no padding
in `PackedMap`.
* Replace `VoidFieldTypes` with `useAllFields`; this eliminates the need
for `voidFieldTypesDiscardHelper`.
(For internal tracking: fixes STAB-1035, STAB-1036, STAB-1037,
STAB-1038, STAB-1039, STAB-1040, STAB-1041, STAB-1042, STAB-1043,
STAB-1044, STAB-1045)
---------
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Co-authored-by: Claude Bot <claude-bot@bun.sh>
Co-authored-by: Claude <noreply@anthropic.com>
